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MG Midget and Sprite Technical - Good news bad news
| Just started the engine of my rebuild for the first time. Good news is that once the timing was sorted the engine started up pretty easily and seemed quite smooth without fettling. Then after about 5 mins it started producing prodigious amounts of smoke from the exhaust :-(. I'm pretty sure the smoke was white so am guessing head gasket. Pulled the plugs and all bar number two look great. Number 2 produced loads of steam when I pulled it ( head gasket again) Rather annoying. I have rebuilt the bottom end, rebore, new pistons etc. only thing in the whole car that wasn't rebuilt was the head which came with a pile if spares. Looked clean. Valves all tight. Checked flatness. Seemed ok. But was slightly worried about my ability to measure accurately. Guessing I should have had it skimmed. Darn! Tim |
| T Dafforn |
| Bad luck! I would get the head crack tested. I suspect that if it just needed skimming, your gasket would have blown between cylinders, and two adjacent ones would show evidence of the leak. Just on one suggests a different kind of problem. |
| Guy W |
| Bad news indeed: I'm with Guy here, I'd wager a beer you'll find a crack between the valves on #2 cylinder. If that's the case and you end up buying a new head, have the new one crack tested. I learned the hard way after spending a small fortune on a 4AGZE head (ceramic coated combustion chambers, sodium cooled valves, flow bench ported... it was exquisite. The best sprinkler I've ever owned.) |
| Growler |
| Makes sense. Will pull the head this weekend. Might buy a recon one. Tim |
| T Dafforn |
| Would it be worth simply trying a new Payen head gasket - after cleaning up the mating faces? |
| Mark O |
| Not sure it would help as I built the engine up with a new head gasket. I think it was a payen one. Tim |
| T Dafforn |
| Not sure whether this is linked, but the cylinder head I used seemed to already have hardened valve seats. Part of the reason that in used it. Could a bad valve seat job cause a head to crack? Tim |
| T Dafforn |
| Early Cooper S 12G940 heads were prone to cracking due to the big valves, and Sprites have the same casting only with smaller valevs. It's possible that removing material to fit hardened seats could introduce the same kind of weakness. |
| Growler |
| If the valves were 1.44 or larger and an ex larger then 1.15 then id sayba crack between the valves is a reality What might be possiable is to put a hardened seat in the intake The idle size for big valve is 1.401 and 1.15 Prop |
| Prop and the Blackhole Midget |
| Hi chaps, Thought I'd update you all on this. Went on holiday. Came back and thought I'd try a new payen head gasket and studs just to check that my head gasket failure was not assembly issues. Anyhow, same result, car started and idled ok. Then after about 60 seconds, loadsa white sweet smelling smoke from the exhaust. Disassembled engine. Oil/water in all bores. Checked the head and block with a straight edge. Inconclusive. Using one edge of the straight edge I get a gap in the middle of the head. Using the other side I get a gap at one end of the head. So I guess my straight edge is not straight! Anyhow I have sent a spare head have off for recon. Just hope the block is ok! (Any one know whether blocks warp as much as heads?) Tim |
| T Dafforn |
| Tim, I feel your pain regarding your cyl head problems. Before refitting it (whether 'reconditioned' or just skimmed), one way or another, do get it pressure tested for any crack(s). 'Reconditioning' may not involve pressure/crack testing - but it needs to be done. Hunt around, you should be able to get a pressure test done for approx £40. More likely circa £55. But it will be worth the reassurance that you are not working with a cracked head. Even a second-hand head - it needs to be crack tested. There is a reason that cylinder heads appear in breakers yards . . . . |
| Andy Hock |
| Thanks Andy. It is very frustrating as this is close to the last part of A 4 year rebuild. Should have known better really. I bought an engine for the car that was running but needed reconditioning. Reconed the block but decided to use a head that came in a pile of spares that I got with the car. I made this choice because the head had valve seat inserts which I thought might be unleaded tolerant and the valves sealed well with the paraffin test ( the one that came with he car needed a valve job). I am guessing now that the reason o was given the head with the car was that it was bu£&ered. DOH! tim |
| T Dafforn |
| Tim wrote>>decided to use a head that came in a pile of spares that I got with the car. Andy replies>> My tale of agony begins in a similar way. (Although not my midget) I was sold a 'running engine' from by a mobile mechanic. Rather than fit the entire engine, I decided to remove its head and just use that to replace my visibly damaged head in my car. I had the >>running engine's<< head reconditioned (ie skimmed, valves lapped in etc etc). I then fitted that head to my car. It was two or three days' work. One hundred miles of use, I noticed oil deposits forming in the coolant water. And then I noticed excessive pressure within the coolant hoses (ie 'hard hoses' when the engine was hot). Despair set in. I again removed the head and had it pressure checked. It was confirmed that a hairline crack was present between combustion chamber #1 and the water jacket. The head that I was sold was complete scrap. I decided to buy a completely new head (the car is a '95 Astra) and start again with cut/ground valves, etc etc. I learnt my lesson. If at all suspicious, ALWAYS check the head for cracks before skimming/recon and fitting. For the sake of £40 or £50, it will save immeasurable agony. |
| Andy Hock |
| Tim, if you need the motor testing, there is no better A series builder than Southam Mini Metro Centre (Southam Motorsport ) in Napton on the hill near Southam. Rod Taylor is the contact name and the number is 01926 815681 tell him I sent you. Hope you get it sorted |
| J L HEAP |
| Hi J Heap, Brilliant tip. Will get onto him test head when it returns Tim |
| T Dafforn |
| Tim, Need to find the source of the water getting into the bores, water in all of them makes me wonder if an intake manifold water leak, what engine is it? I had a failure years ago that I assumed was a head gasket failure. I was cruising along the M4 at the time and felt a slight drop in performance and when I looked in the rear view mirror I had a great cloud of white smoke behind me so stopped and got recovered. Had the head skimmed and back on it ran great briefly dry so topped up the water to have it sputter and run bad. Intake manifold off and I had a pin hole leak into 1/2 inlet tract (A series) and a wee fountain. A nice ported head scrapped, luckily I had a spare. I did try to braze it but without success. BTW a mate some years back had an A head with a crack between inlet and exhaust welded by an old boy that was reputed to perform miracles and that seemed to work well all the time he had the car on the road after the repair. He welded it and we re-cut the seats. |
| David Billington |
| Interesting. I am using a single carb manifold. With water heating I did notice that there was signs of water in the inlet manifold. I also didn't see any bubbling in the water in the rad but I don't think that I had run the engine until the thermostat had opened. I'll have a look tomorrow. Tim |
| T Dafforn |
| Just been down to the garage to have a look at the inlet manifold. Looking down the manifold with a torch I cannot see anything obvious. Also tried blowing down the pipe with one end closed and it seems ok although I guess the true test is to pressurise it with water from the tap. The pipe in my manifold is copper so I am guessing it hasn't corroded. If it has failed I guess it must have been breached during machining. I'll check some more tomorrow. Tim |
| T Dafforn |
| Hi chaps Have been looking through the archives and interestingly there is a long thread in 2006 that describes exactly what I am seeing. Eg new engine smoke from exhaust shortly after starting Smoke at idle less at open throttle Dime sized oil drops on all cylinders Oil in inlet manifold In this case the issue was the combination of high manifold vacuum combined with possibly slightly higher crankcase pressure as rings have not bedded in. This leads to oil being drawn up the breather into the carbs. I seem to remember another thread on this in the recent past. Can't test whether his is what I have as have sent the head for rebuild. But sounds possible. Tim |
| T Dafforn |
| Maybe, Tim. But l thought that you said the smile was white and that what you were getting was steam. |
| Guy W |
| Yes that's what I thought first time I ran it but I didn't run it for long as I was worried about doing damage. Second time it could have been bluish. But what was clear was that there seemed to be oily residue in each cylinder and the intake. Probably just have waving and should wait til the reconned head returns. Cheers Tim |
| T Dafforn |
| Tim: the suction of oil up into the manifold from the crankcase breather is a much discussed and disputed phenomonem. I believe it usually happens with the mushroom-shaped pressure control valve mounted onto the top of the inlet manifold rather than a direct connection into the body of the SU (no pcv). The whys and wherefores are a minefield and generally divides owners into two categories: those who say it can't happen and those who have disappeared in a cloud of smoke. I fall into the latter category. When you reassemble watch out for this one. BTW in my case compression tests showed no issues which could lead to excess pressure in the sump. Cue: Lawrence on this one |
| G Williams (Graeme) |
| Graeme, I know what you mean this seems to be on just a little less contentious than front wheel bearings. One issue with my engine maybe the non stock setup. It has a single HIF44 a la vizard with the breather connected directly to the inlet manifold. The suction it creates is pretty strong, certainly it feels strong when my hand is over the oil filler. I didn't plumb in a pcv but I do have one that I can fit if need be. I think the key anomoly is finding the same oil droplets in all four cylinders and residue in the inlet. Would oil get into the inlet from a knackered head gasket? Surely that would be going against the flow! Cheers Tim |
| T Dafforn |
| I too have HIF 44, and cranckcase breather plumbed into manifold, but via PCV - no issues with burning oil. I would strongly suggest you do similar and see what happens. The manifold depression is far too great unless controlled by the pcv, and as such, chances are you will be scavenging neat oil from the crankcase. As an aside, you can plumb the breather directly into the body of the HIF 44. Whilst this may cure your oil issue, I found it to be inadequate to maintain a slight vacuum in the crankcase. Perversely, now not enough suction. The result of this scenario is that the crankcase over-pressurises the scroll seal at the rear, and the car leaks oil underneath from the crankcase. Fitting a PCV appears to have cured both scenarios for me. May also be worth looking at the "oil seperator" on the timing chain cover and seeing if it is blocked up. Cannot see that it does that much, but I guess retruning it to how it should be is not a bad idea. |
| Mark O |
| Hi Mark, thats good to know.. I had wondered about the vacuum port on the HIF44 when I was assembling the engine.. Went with the one on the manifold because it fitted with the piping.. I know the Oil separator is OK as I cleaned and replaced the innards as part of the rebuild.. Cheers Tim |
| T Dafforn |
| On a fresh motor you'll always need to accomodate crankcase pressure and plumbing the breather directly into the inlet manifold is a recipe for a major smokescreen. Just try it on the overrun for maximum effect! I find on a rebuilt engine it's better to keep all breathers open to atmosphere for the first 1000 miles or so, then install the PCV.Some engines need top hat stem seals on all the valves - don't reuse old ones as they work harden and can split - this will also show as oil in the inlet manifold. You can bypass the inlet manifold with more heater pipe,to check with and without,and agree that Rod at Southam IS the man. |
| F Pollock |
| I ignored this thread, as the description included water. But I did suspect oil sucking, because, apart from the water, everything else matched exactly my experiences with two separate engines. Oil sucking may be disputed by some, but that's because those people haven't experienced 'exactly' what I and quite a few others have experienced. And now it seems one more can be added to the list. In the pic below you can see where the connection should be made on the HIF without the PCV. As suggested, if using the manifold connection you have to use the PCV. The only real dispute about this oil sucking condition, is exactly why it happens. Because it does happen. Is it too much crankcase pressure, or too much vacuum, or too slow drain back of oil from the timing cover into the sump, or too much oil feed into the timing cover in the first place? Or is it a combination of all those factors, with one or two of them having more significance than others? The current and previous engines in my car BOTH did it when I first built them. I lived with it on both because when the engines reached a certain temperature, the sucking stopped and the car could be driven normally. Then a few years later, on the current engine, I swapped the twin SU's for the single HIF SU below. The oil sucking has stopped. Was this due to reduced vacuum at the take off point on the HIF, or due to the rings having bedded in, or a combination of the two? I don't know for certain, but I suspect less vacuum. The reason being that on the previous engine, I did over 100000 miles, and the oil sucking was present for the whole time when the engine was cold. Clearly the rings had bedded in by then, and apart from when the engine was cold, the engine didn't consume more oil than it should, and didn't smoke either. So as an experiment, as I'm due to rebuild the current engine, I'm going to swap back the twin SU's and see what happens. I'm also going to try various experiments on the previous engine and see if I can cause the timing cover to fill with oil.  |
| Lawrence Slater |
| Tim Try it by all means. If you already have the PCV there is nothing to lose. Block off the breather port on the carb though. Mark |
| Mark O |
| Hi Lawrence I think I remember your thread now. Amazing how such a simple thing can be contreversial. My guess as to why it may not happen when the engine gets warm is that the viscosity of the oil drops allowing it to drain quicker from the front cover. One experiment that i could do is to monitor the vacuum at idle as the engine ages. Could also attempt to measure crank case pressure at idle. Cheers Tim |
| T Dafforn |
| "when the engine gets warm is that the viscosity of the oil drops allowing it to drain quicker from the front cover." Yup, I agree with that. But the engine should be able to cope with cold oil. If it can't, then is the timing cover too full, or the crankcase pressure too high, preventing the oil draining back into the block?. I can see this will run and run. lol. |
| Lawrence Slater |
| Yes it is strange. One possibility is that the vacuum drawn from the single carb inlet manifold without the PCV is just too high. I know for the spitfire engine which had no pcv the vacuum is drawn from the carb in a position that I don't think experienced the full inlet vacuum as mentioned earlier in this thread. Otherwise I can see that direct manifold vacuum would need a pcv. It could also be that he timing chain case is over full and that can only be due to over feeding or low draining. The former seems unlikely to me, but it is possible that drain holes become obscured. I tried to be fatidious with my use of sealant when putting the cover in place so would hope this didn't happen! O well! This could all be a academic if the new head and disconnected breather don't work! Tim |
| T Dafforn |
| I'm not sure how the 1500 breaths, or if they've ever suffered from this. But on the A series, connecting directly to the manifold without a PCV will definitely suck up oil. When the vacuum is high at the manifold, for example when the carb butterflies are shut on the overrun, the valve in the PCV should close off the opening to the timing cover pipe. Without that happening, there's so much suction, that along with the crankcase pressure resisting oil drain, by effectively pushing the oil back into the timing cover through the small drain holes, and the oil feed from the end of the camshaft, the timing cover fills up. As soon as it covers the breather canister hole, up goes the oil into the engine. There's less suction on the twin y piece carb connection setup, when compared to connected directly to the manifold, but nevertheless, on my engines, and others have reported the same thing, oil can still be sucked up for whatever reason, -- as yet still not really determined. I haven't measured it, but it seems apparent that there's less suction at the carb connection on a single HIF, when compared to the Y piece connection on twin carbs. But if less suction obviously solves the problem of oil sucking, it doesn't relieve the crankcase pressure and stop oil being pushed out of the rear scroll. So I'm still trying to get to the bottom of what happens. But I'm certain it's not the drain holes per se causing the problem. I think the timing case 'has' been over fed with oil from the camshaft front bearing. The camshaft end-plate, fitted flush against the engine end-plate, limits the amount of oil fed into the timing cover. But if either of the end-plates are distorted or very worn, more oil can escape from the end of the cam bearing, rather than the measured amount that's supposed to be delivered on each revolution of the camshaft. This coupled with sufficient crankcase pressure, possibly aided by increased suction, allows the timing cover to fill. There must be a tipping point. Just enough crankcase pressure, coupled with just enough oil over feed, along with thick enough oil when the engine is cold. Or maybe, the crankcase pressure lessens when the engine warms up as the rings seal better against the bores. This seems unlikely, as over the miles this should cure itself as the rings bed in. But it never did with mine. So my money is on too much oil in the timing cover when the engine is cold and the oil slow(er) to drain back into the block. I've wondered about drilling an extra hole in the block face, below the critical level where the oil can enter the breather canister. But when the oil is warm, if the oil drains too quickly, it could starve the timing chain and gears of lubrication. Also, would this extra hole weaken the block face? Or maybe enlarging the existing drain holes in the front main cap. But would this weaken the main cap too much? One other thing occurs to me. Could it be exacerbated by having larger inlet valves in the head? An engine, near to the tipping point might not suck oil. But then, could adding larger inlet valves into the equation, give it just enough more suck to pull up the oil? But I'm guessing Tim has standard valves, as he has a spare head, and less likely to have 2 big valve heads than 2 standard ones. Also, when this first happened to me back in the late '70s early eighties, I had a standard 1275 head too. |
| Lawrence Slater |
| Lawrence, I don't think your and Tim's issues are exactly the same. Tim's is clearly to do with too much suction due to incorrect vacuum connection. Yours, I think, is too much oil in the chain case. Maybe yours is / was occurring when accelerating immediately after heavy braking, causing oil surge in the sump so that oil overflowed through the window into the chain case, and then got sucked up by the vacuum system. Aggrivated by cold oil, and other factors you have identified. It would be interesting to find out if using a baffled sump might have cured it. |
| Guy W |
| Guy, I agree. Connecting directly to the manifold without a PCV will cause a lot more suction, and it's quite possible/probable, that when Tim connects one, or connects to the reduced suction of the carb, his problem will be cured. But too much suction alone can't cause the problem. It needs a sufficient level of oil in the timing cover in the first place, for the suction to "grab hold" of the oil, pull it up the breather pipe, and into the manifold. As regards it not being the same as mine, Tim wrote in the 1st post "Then after about 5 mins it started producing prodigious amounts of smoke from the exhaust :-(." That's precisely what I experienced when it first happened to me many many years ago, directly after starting a rebuilt 1275 engine for the 1st time. I was using a PCV at the time, but swapped to the Y connection on the carbs. That 'didn't' cure it completely. Subsequent to that, it doesn't require the car to be moving. But usually within 5 minutes of starting the engine, I'm on the move. It needs suction, so inevitably it happens on the overrun, not when the throttle is wide open. But once it starts, opening the throttle makes it worse. No doubt oil surging forward under braking doesn't help, but it's not the cause. If it was, it would be a lot more common. |
| Lawrence Slater |
| Suction upstream from the butterfly - I.e. when using the carb connection, is greatest at WOT. It's only when connected downstream of the butterfly, I.e. to the manifold, that suction is greatest on the overrun. Suction is also proportional to the swept volume of the cylinders so is dependant on the volumetric efficiency and the revs. |
| Guy W |
| Guy - you forgot the temperature and air pressure ... |
| Chris at Octarine Services |
| Yup your right Guy it happens on the overrun with the PCV not the carb connection. It's been at least 13 years since I had the problem at all, because I swapped to an HIF, and it hasn't happened since, so my memories aren't what they used to be. But I won't be suprised if I fit my twin SU's back on and the oil sucking happens again. Temperature definitely has a part to play, because it most often happened, but not only, in the winter when the engine was cold. In the summer months it only happened on early chilly mornings. That has to be the oil viscosity factor. I can't see air pressure having much to do with it, although I never checked the occurence against a barometer. ;). |
| Lawrence Slater |
| I'll have to get on with my experiments on my spare engine. All I need to do is cut a viewing window in the spare timing cover, spin the engine, watch the oil enter the cover, and see how high it rises before it drains out via the main cap and the hole in the block face. I'm going to vary the gap behind the camshaft endplate, to see how it affects the oil feed. |
| Lawrence Slater |
| I think Chris was meaning that temp and pressure affected the vacuum pulled by the engine. Which is true, but would already be included as factors in the calculation of volumetric efficiency. Lawrence, I suspect that your perspex window idea will instantly be so smeared with oil splash that you won't be able to judge the actual oil level with a spinning engine. Is the exit hole out to the oil canister baffled on your engine ? |
| Guy W |
| It's an unknown as yet Guy. I'll have to experiment. First I'll try it with a clear window, but if it is too smeared, then I'll run without. One idea I have is to take off the chain and spin the cam directly to prevent splashing. For that I'll cut a hole over the cam nut and put a socket on it, rather then spin the engine from the crank nut. No, my timing cover doesn't have a baffle. That's a good thought. I wonder if baffling the lower section of the entry hole to the breather, thereby raising the level for oil entry to the hole, might prevent sucking? My thinking is that it wouldn't help, because the 'vacuum' needed to suck the oil up the pipe as a solid column of oil, doesn't occur until the entry hole is fully covered with oil anyway. As long as the oil isn't fully covering the hole, air and fumes can still be drawn up through the pipe. It must only be when the oil covers the hole completely, that the vacuum suddenly grabs the oil. Then as the engine and thus the oil warms and gets thinner, draining exceeds filling. But I wonder how many timing covers are baffled as a ratio to those that aren't. Could it really be as simple as that? Inspite of my theory about the hole needing to be fully covered, could it only be engines with non baffled timing covers that experience oil sucking? But then you'd have to ask why those engines didn't suck oil straight from the factory. Additionally, a baffle might make it worse, preventing draining from the timing cover breather. |
| Lawrence Slater |
| I am not sure if they are baffled. I can't really remember but seem to think that mine is. But I may be imagining it though. That is why I asked. I am still not convinced that Tim's is the same issue. Same symptoms don't always arise from the same cause. |
| Guy W |
| Here's my timing cover from the inside, baffle-less. Assuming Tim's engine is delivering a continous column of oil to the manifold, and as the described symptoms are the same, the only place it can be coming from is the timing cover. So essentially the cause is at least related. In tim's case, running without a PCV on the manifold could well be the problem. But I still argue that there has to be sufficient oil in the timing cover to initiate the oil suck in the first place.  |
| Lawrence Slater |
Here's a little comparison from early to late timing covers - with the increased prominence of the splash guard on A Plus.
 |
| F Pollock |
| Yep I remember that pic from the long engine breather thread Fergus. As you imply, there must have been a good reason for the evolution of that ring(baffle?). |
| Lawrence Slater |
| I can see a scenario that with a high enough oil level in the cover, and without an effective splash guard, the timing gears and chain could effectively fling oil directly into the open port.And from then on it's hello Mr Bond. But this debate will probebly run forever. What would help would be to speak to someone who worked in powertrain development - Mike Theaker perhaps. |
| F Pollock |
| Who is Mr Theaker, and who are powertrain developement? |
| Lawrence Slater |
| I suspect that it is not just oil splatter flying off the chain. That will fly outwards away from the centre which is why the orifice is centred on the cam socket. But with the chain moving fast in a bath of viscous oil it will draw up a substantial standing wave. This should overflow through the front plate window but It seems that under certain combinations of conditions, it doesn't all escape. |
| Guy W |
| If the pcv doesn't work I may have another option. My engine is a marina engine with a high oil filter which means it has a mehanical fuel pump hole. I am pretty sure that the mini guys sell a blanking plate for this with a breather. I am guessing this would provide a route for he vacuum with no oil issue. Cheers Tim |
| T Dafforn |
| Agree with that Guy.Move to the top of the class. |
| F Pollock |
| Well, I got blue smoke, on tickover with a hot or cold engine. Connection from crank case breather through pcv to tapping on manifold. Significantly, it only happened when the oil was close to max on dipstick, not when nearer to "min". And yes, I checked for correct dipstick by draining oil and filling with correct number of litres. I drove around for weeks with no problems until I topped up the oil. It was a new pcv - I can only assume it was working ok. At one point the car kept running on the oil sucked over - turning off the ingintion didn't stop it! |
| G Williams (Graeme) |
| "This should overflow through the front plate window but It seems that under certain combinations of conditions, it doesn't all escape." And those conditions are when the cover has too much oil in it. Question is. Why does it have too much oil in it? |
| Lawrence Slater |
| Tim, I've just read your comment that you have a Marina engine. That wouldn't originally have had a PCV would it? But I think it could have had the middle of the three timing covers that Fergus posted, with the 3/4 spash ring. If it has got that 3/4 splash ring, and when you connect to the HIF connection rather than the manifold, you still getting oil sucking symptoms, that rather mitigates against it being an oil splash problem, and leans it much more to a timing cover overfill problem; -- for whatever reason. But with less suck from the HIF, it may go away altogether of course. With Graeme, Tim, and me included, I now have a list of circa 20 people who have reported these exact same sysmptoms on 20 different cars. Very few of the total number of cars made are represented by posts on this BBS, so I reckon that this problem was(is?) a whole lot more common that is believed. The reason it hasn't been heard about much, is that most people misunderstand and misdiagnose it. Most often it's dismissed as rings, valve seals, blocked pipes etc, and lot of engines run without the breather connected. I've started experimenting on my spare engine, and when I get some more results, I'll start a seperate thread for it with an apt title so it makes more sense when looking in the archives for it later. |
| Lawrence Slater |
| Hi Lawrence Unfortunately although it is a marina engine, it is running with a midget chain cover. The marina item doesn't work well with the midget front plate without modification. Didn't have any ancillaries with the engine when I bought it so don't know about PRVs. Wondering about tapping the vacuum from the HIF44 rather than the manifold by might measure vacuum vs throttle position to get a real idea of the situation. Cheers Tim |
| T Dafforn |
| Regarding measuring the oil level in the front cover. Why not just drill it and put in a siting tube like you have on old heating oil tanks. Tim |
| T Dafforn |
| You mean use a dip stick? Not sure I understand what you mean Tim. What I want to do is watch the timing cover fill up, hence the idea of putting in a window so i can see what's happening. |
| Lawrence Slater |
| Sorry Lawrence wasn't being clear. Drill a hole in the bottom if the cover and attach a clear pipe. The level in the pipe will then match that in the case. ( sighting tube) Tim |
| T Dafforn |
| Ah yes, I get you now. Good idea. I have some clear tube, all I need is a way to seal the pipe into the cover. I think I can do that with a plumbing connecion. I'll have a rummage in my plumbing stuff tomorrow. |
| Lawrence Slater |
| That will give a reasonable indication of a moderately static oil level, but will not necessarily reflect the oil wave effect of a duplex chain pulling oil into the surge that I think is probably occurring. If anything, the sight tube level could drop under these conditions. |
| Guy W |
| Yup was thinking that too Guy. If the pipe's too big, it will increase the capacity of the timing cover. The sprockets and chain already take up a fair portion of the volume, unless the pipe's quite small, it give a misleading reading. But too small and the oil, being quite thick compared to water, may not rise properly in the pipe with all that washing machine like action going on inside the cover. |
| Lawrence Slater |
| I've reactivated the previous long "engine breather" thread from last year for my expeiments, as it continues on with all the posts and pictures in that thread, and I think it will be more useful to try and keep most of it in one place. Also, Tim's problem may well turn out to be caused purely by too much vacuum from the direct connection to the manifold. If not, then the other thread might contain the answers. |
| Lawrence Slater |
| O yes, and to answer another of your comments Lawrence... RE: the cam thrust plate, the one on my rebuild is new as is the cam.. So hopefully I am only seeing oil coming out where it should be.. Tim |
| T Dafforn |
| Yep I think most people who've rebuilt their engines have also used a new cam endplate too. And most people who've reported this problem have also just rebuilt their engines, but not all. Some have re-built it some x number of miles previously, and the problem hasn't started until quite a while later. Add to that, many people have "hotter" engines and don't get this kind of oil sucking. So why on some engines and not others? Why on some engines would the timing cover have enough oil in it to be sucked up the breather, and not on other engines? Splashing from the chain churning the oil in the cover is a constant, on ALL the engines, and yet some don't have a problem, even with high compression and hot cams. Some have high crankcase pressure, as evidenced by oil scroll leaks, but they don't have oil sucking. So, if not the cam endplate, which definitely incorporates a designed oil feed to the timing cover, what else could it be? I have to admit, if mine isn't fixed by fitting a new cam endplate, then I'm as stumped as I was when it first happened to my engine back in the early eighties. |
| Lawrence Slater |
| Lawrence, one thing I have noticed is that the overflow window into the block consists of a sand cast recess that looks as if it has been knocked out in the factory to create the opening. Not sure that that is how it was done, but it looks a bit like that. Perhaps if this is the case, some windows are either larger than others, or the lower lip of the opening varies according to how accurately the hymen was penetrated. Could affect the overflow level between otherwise very similar spec engines? |
| Guy W |
| That maybe it Guy, or maybe it's the variation in cranckase pressure in some engines? Hope you don't mind if I answer more fully in the "engine breather" thread I reactivated. I'm keeping a copy of that thread, and it's easier to follow all the nuances if they're in one place. |
| Lawrence Slater |
| Not following that thread Lawrence. As with the Wheel bearing one the very long threads, especially with lots of photos, just become too slow to load for practical use on rural broadband speeds! |
| Guy W |
| Didn't know you had low bradband speed Guy. I've only got a bb speed of 1.5 to 2MB/s, and i can load it ok. Is yours slower than that? I should have started a new thread then it seems. I could always start another and copy the most recent posts into it? But I suspect there may not be the interest lol. |
| Lawrence Slater |
| Generally around 0.7 down and 0.4 upload speeds. Annoying when BT keep wanting me to upgrade to a 24 mb/sec account and just don't understand that some connections just cannot even handle their basic 8 mb/sec service. |
| Guy W |
| Yup that is slow. That's not much better than a modem connection of old on the download. Sometimes I get as much as 4MB/s download, but not often. The explanation I get, is that capacity on the line from the exchange to the service provider(plusnet) is limited, and when others are using it, the through rate drops. I'm also told the distance from my house to the exhange is a factor, along with the ambient temperature, and age of the copper cable going to the exchange, which was only ever designed for, and can still cope with voice signals. All of which makes sense I suppose. At the same time though, they want me to upgrade to fibre optic. So I'm a bit doubtful and I suspect they don't really want to improve my signal on copper, so they can sell me a more expensive 100MB/s fibre signal that I don't need. |
| Lawrence Slater |
| Really not sure about the relevance of crankcase pressure here? If it was an issue we would see two populations of engines having an issue with oil blowby.. One would be new engines prior to bedding in piston rings while the second would be the old tired engine where the rings are worn.. Lawrence, do you see this ? I do think that the way the inlet is linked to the timing chain cover must have an influence.. There seem to be a number of options for this: 1) no connection (do these cars just dump oil out of the breather into collection bottles if attached 2) direct connection to inlet manifold (probably the worst case, and what I had..) also need to consider whether the manifold is for a single or dual carb setup 3) connection to inlet manifold with PCV 4) direct connection to vacuum ports on SUs, again need to consider dual with or without y-piece or single carb setups 5) connection to vacuum ports on SUs with PCV these all add extra variation to the results.. On a side note it would be good to know the vacuum level from the inlet and SU.. cheers tim |
| T Dafforn |
| Tim To confim....Have you tried the PCV attached to manifold and breather as discussed? |
| Mark O |
| Will do when I get the head back from reconditioning next week :-) |
| T Dafforn |
| I was going to post this on the other thread for better continuity, and easier searching the archives in the future. And because Tim's problem may be simply due to not using a PCV. However, unfortunately it seems that thread might have lost interest due to it's length and the time taken to load. It's a shame as all the arguments have mostly been aired in that discussion, and will no doubt be repeated here again. But I'll ramble here instead, because I think I now have the answer – yet again-- to why oil sucking happens in a lot of engines for no obvious reason. If I assume(for now at least) that I'm unique in fitting a badly knackered camshaft endplate on my spare engine, and have a worse case of oil sucking than anyone else, then "if" that's the case, the distorted camshaft endplate is a red herring. But I have a 2nd engine that has oil sucking, and the question remains, why do some other engines in which perfectly good new camshaft endplates have been fitted, also suffer from oil sucking? Firstly, I found the answer to my question in the other thread about the "vent/overflow/casting" hole, in a picture Guy posted back down in that thread of a 948cc engine. That engine has the same hole in the same location as the later engines. Therefore, it can't be a crankcase vent hole, as there was no breather in the timing chain cover of the early engines. If it was just a casting hole, why not cover it with the engine plate? Why make a bigger hole around it in the front engine plate? So it's clearly there for a purpose. I'm 100% certain it's not a splash feed to lubricate the chain. In my experiment spinning the engine, -- there wasn't a single drop of oil expelled from that hole into the timing chain cover. Instead, oil is delivered into the cover under pressure from two sources. From the end of the crankshaft front main bearing, and from the end of the camshaft. It initially collects at the bottom of the cover, and provides plenty of oil for the lower section of chain and sprocket to run in a bath of oil, and carry oil up with it as the crank rotates. So all that's left for the hole in the block face is as an overflow hole. But why would you need an overflow hole? Especially if there's no breather for the oil to flow out of, if the cover fills up. The two small drain holes in the front main cap, could be overcome by the oil feeding in from the front camshaft and main bearings. This might well happen when the oil is still "cold" and hence thicker, and won't then flow so easily back through those two small drain holes. Also, apart from the constant flow of oil from those two oil feeds, there's also crankcase pressure, blowing the oil back into the cover, or at least resisting the oil being drained through those two small holes in the main cap. If there wasn't an additional drain hole higher up, the cover could completely fill up with oil. With a constant oil feed, and crankcase pressure being applied in the timing chain cover, oil would very likely be forced out of the front crankshaft oil seal. So there's an overflow hole to take the extra oil back into the sump. The overflow hole in the block was introduced before the breather in the timing chain cover was introduced. It must have been expected that the oil could reach that level, but the overflow hole would prevent it rising above that. I doubt it was expected that the oil would rise above that overflow level, but in some circumstance it must be above that level for oil sucking to happen. When the timing chain cover breather was introduced, the entry hole to the breather canister on the inside the timing chain cover, was set at almost the same level as the overflow hole in the block. In fact the bottom of the entry hole to the breather canister, sits BELOW the bottom of the overflow hole in the block face. So BEFORE the oil starts to flow through the overflow, it is already flowing into the breather canister. So now with sufficient crankcase pressure, and some suction from the breather, with an already high level of oil in the timing cover, the lower oil drain holes and overflow are completely overcome, the timing chain cover fills to the top of the breather inlet hole, and up goes the oil into the manifold or carbs. But not all engines have the oil sucking problem. So what common variable(s) applies to those engines that do? All the engines, new or old, have crankcase pressure, but that varies due to wear in the engine and or modifications. Assume the oil feeds from the front main and camshaft bearings --- ignoring oil pressure for now ---, and the drain hole sizes of the main cap and overflow are considered fixed, but the crankcase pressure and strength of breather suction can vary. So maybe those latter two factors alone can combine to cause the oil in the timing chain cover to rise sufficiently above the overflow level to commence oil sucking. Higher than "normal" crankcase pressure will pose even more resistance to the flow of oil back into the sump via the drain and overflow holes. At the same time, breather vacuum applied to the timing chain cover canister, from the inlet manifold or carburettor connections, will also pull on the oil, and slow down the flow rate through the lower drain holes and the overflow hole, causing the oil level to rise high enough. So I reckon those must be the cause(s). In all engines the oil can reach quite high levels in the timing chain cover. The overflow and drain holes cope well enough with normal crankcase pressure and when there isn't too much suction from the breather. But in engines with either too much suction or crankcase pressure, alone or combined, when the oil is thick enough(usually cold), this causes the timing cover to fill with oil to a level that completely covers the breather entry hole. Then the oil is grabbed by the suction and pulled into the engine. When the oil warms up, it gets just thin enough to drain fast enough. But if there's too much suction or pressure the problem continues. Here's a picture I took yesterday, combined with a sketch of measurements, I posted in the long other thread last year. It's a view looking forwards from behind the engine front plate, into the timing cover behind it. It shows the relative heights of the overflow and breather canister entry holes. My biro cap indicates the centre of the overflow hole in the block face.  |
| Lawrence Slater |
| Guy, Have you asked neighbours or looked up broadband speed rating sites for your area. Is your speed typical for your area and distance from the exchange. I'm on about 6mbps down at the moment and the exchange is over 1.5 miles away. A couple I know maybe 200yds down the road were with BT and were amazed at the speed I get as they got very poor speed and reliability and BT weren't helpful just saying that's what you get, they're now with TalkTalk and improved. Looking at a speed rating site for my area BT seemed to consistently be the slowest, I'm with Zen. |
| David Billington |
| PS Tim. You asked about degrees of vacuum at the manifold. My Smiths gauge deflects from 0 to 30-InHg. When cruising and resting very lightly on the throttle, my gauge reads circa 20. Coming off the throttle at high revs, momentarily sends the needle all the way to 30, but it's often over 20. I don't know what it is at the carb connections, because my gauge isn't connected there, but probably similar/same as the distributor vacuum take off. Vacuum advance on a standard 1275 Spridget it's quoted as finishing at 8-Inhg. Whereas on an Austin 1300GT for example, it's quoted at finish at 18-InHg. So at least 18-InHg I'd say. How much is needed to lift a column of engine oil? Mercury weighs a lot more than oil. |
| Lawrence Slater |
| Hi Lawrence.. Good summary.. possibly only a slight clarification.. For the early engines without the breather I don't think the crankcase pressure is driving anything in the timing chain cover. The cover is contiguous with the crankcase and without the breather (open to atmos or vacuum) there is no pressure differential.. therefore the level in the timing case would not be effected by the crankcase pressure. I bet that the addition of the breather/vacuum system in later engines was purely to solve the scroll seal leak issue. This would have become more important as time went on and it became less acceptable to have a leaky engine in a new car. However adding the breather effectively added a route to a lower pressure system and a new issue was introduced (e.g. the potential for oil to be driven up the breather.) Again in this system I am not sure that the crankcase pressure drives the oil into the timing chain cover (the presence of the second opening into the crankcase (the overflow)) would prevent that. But it would certainly drive it up the breather if the oil level were to reach it.. If this is true then there are two causative factors for oil moving up the breather. 1) excessive oil entering the chain cover (through leakage from the front plate, overfilling or something else) 2) positive pressure differential between the engine and the breather Given that the pressure differential is present to some extent in all engines with a breather then it is likely that excessive oil in the chain cover is probably more important, although given my current issue it is also possible that V high vacuum may also be an issue? Please forgive me if this is what you already said! Cheers tim |
| T Dafforn |
| "The cover is contiguous with the crankcase and without the breather (open to atmos or vacuum) there is no pressure differential.." -- But is that the case? With only the small hole in the block face, would that be enough to equalise the pressure? Also there would be air in the timing cover, and that compresses. But maybe your right and the "overflow" hole was first added, to prevent oil being blown out of the crank oilseal under pressure from the crankcase. Also, I don't(didn't mean to imply) say that crankcase pressure drives the oil into the timing chain cover. I say it resists the flow of oil back into the sump via the drain holes and the overflow in the block face. This must be so once the breather in the timing cover is introduced, and with the addition of suction, the effect must be magnified, to the extent that draining slows down and is overcome until the oil thins with heat. "1) excessive oil entering the chain cover (through leakage from the front plate, overfilling or something else)" ---- I ignored the effect oil pressure in my last long post. But that "something else" you refer to could be the oil pressure. Many posters(including me) with this issue, have oil pressure well above 65lbs. Mine easily hits 90+ when cold. Do you have high oil pressure too? Maybe it's forcing excess oil into the timing cover. But anyway. If we assume it's high vacuum, and higher than desireable crankcase pressure, both of which on a newly built non-standard spec engine can't be reduced, what's the solution? If the leaking cam endplate isn't the cause on all engines other than mine, then what else? The high oil pressure issue can be investigated, and at worst the spring in the relief valve can be shortened. I'm not sure I want to try lowering the overflow hole by enlarging the blockface hole, as it may weaken the block. But the other approach is to raise the breather entry hole. Cut the breather out of the timing chain cover, and move it up an inch or two. Again though, I'm not sure I really want to modify the timing chain cover in this way. -- I'll come back to that in a moment. Then there's the addition of another breather point. I was giving that some thought last year. The old timing chain cover I bought, also has a breather canister. It's my thinking to adapt it and drill the side of the block over the mechanical fuel pump take off(just as you're thinking, and fit it there. So when I finally strip my spare engine fairly soon -- hopefully --, I'm going to look at that too. But the camshaft lobe that drives the mechanical fuel pump, must fling a fair amount of oil at the pump. So a baffle of some kind would also be needed inside the side of the block to prevent oil being sucked into that 2nd breather. Coming back to modifying the the timing chain cover. Here's a pic of the cover I bought last year. I believe it's a prototype from a test engine. As the breather canister entry hole is higher in the cover, and the canister sits at the end of a long tube, this may solve the problem without alteration. So I'm thinking of putting my twin carbs back on the engine in my sprite. This sucked oil before i changed to the HIF. If I can make it suck oil again, I can then try fitting this cover to see if it cures it.  |
| Lawrence Slater |
| Lawrence, With the cam sprocket spinning around likely throwing oil outwards I would have thought the cover shown would be more prone to getting oil in the tube. With the production one being situated near the centre of the cam sprocket it would be near the centre of the maelstrom and less likely to get oil in the tube. I don't think the relative level issue has much bearing while the engine is running. Just my thoughts. Maybe you need to make a perspex cover for trial, do you no anyone with vacuum forming equipment or that could glue one up. i don't expect hot oil will help its life but for a short test I would expect it'll last well enough. |
| David Billington |
| Hi Lawrence Looks like we were thinking alone the same lines! I think the overflow hole is probably enough to ensure equal pressures. If it is enough to let oil flow back then it is enough equalise air pressure. I do think that the crank pressure won't drive the oil into the chain cover through the lower drain holes if the pressures are equal. Your observation regarding placement of the vent near the middle of the sprocket is really important. You are absolutely right this reduces the likelihood that the movement of the chain is "pumping" oil into the breather. It think moving the breather is a good idea as I don't want to remove the vacuum totally as it makes good sense. One other thought I had was that if the oil flow from the cam was governed by the differential between the oil pressure and the tank case pressure then having a low pressure in the crankcase would increase oil flow. Hmm this would mean that using vacuum to reduce scroll seal leaks could increase oil flow into the timing chain cover! Interesting? Cheers Tim |
| T Dafforn |
| The positioning of the outlet orifice to the breather canister at the centre of the sprocket to avoid oil splatter was a point I made a couple of days ago. I doubt very much if there is any significant pressure between the chain cover and the general crankcase area. The size of the overflow hole between the two is quite large enough to equalise the pressures between the two compartments under all operating conditions. The amount of suction through the breather pipe is strictly moderated, too. Either by a pcv valve if connected to the greater suction of the manifold, or by connection to the carbs, which suck less. I am pretty convinced that suction through the breather system only becomes significant in this oil smoke belching phenomenon in situations where the oil level rises sufficient to engulf the outlet. Only then is the suction sufficient to have an effect. Relative to the volumes of the combined crankcase and chaincase, the rate of suction is insufficient to draw oil up to any extent until it reached the confined diameter of the breather pipe. |
| Guy W |
| The breather entry hole, may well have been located where it is to avoid oil being thrown in. And from Fergus's pictures of the later covers, it appears that an "oil splash" ring gradually evolved around it. However, placing it below the overflow hole exposed it to being flooded with oil when the level rises. Or maybe the hole in the block face really isn't an overflow hole at all, but a pressure equaliser hole instead. In which case BMC had no idea that oil could reach such a high level inside the timing cover. Guy you said, "I am pretty convinced that suction through the breather system only becomes significant in this oil smoke belching phenomenon in situations where the oil level rises sufficient to engulf the outlet. Only then is the suction sufficient to have an effect." ---- I've been saying that since last year and long before. That's exactly what I observed back in the early 1980's long before the bbs existed. In 1998 I wrote this here on this bbs, 30 October 1998 ------ "the oil is filing up the timing cover and not being able to drain away sufficiently quickly enough when cold and less fluid, and hence getting sucked right into the inlet. And that's the point it only does it when the engine is cold. When it approaches normal operting temp the problem goes away." Nobody knew the answer then. Nor did they know the answer in the BMC technical department (Oxford I think) when I telephoned them to ask about it back in the 1980's sometime. Either that, or they knew, but weren't telling. David, the timing cover in the picture has a baffle over the inlet to the breather. No doubt put there to counter the oil being thrown in there. The small amount that does get in there will fall out again I think. Unless that is, the oil level rises sufficiently to completely cover the hole. But the hole is a lot higher than the "overflow" so I doubt it will. But I won't know for sure, unless I try it. As I wrote in the reactivated thread, I can make a perspex window easily enough, but my drill can't spin the engine for long enough without the risk of burning out the drill. So I've given up on that. As for a vacuum, I've got a hand vacuum pump, but it's not much use if I can't spin the engine for long enough to fill the cover. I think the levels of the breather and overflow holes, are absolutely relevant. If the overflow hole was lower than the breather hole, oil would begin draining through it, "BEFORE" it flowed into the breather hole. In which case if the oil level never reaches the breather hole, the suction can't take a hold and pull it up the canister. As for the crankcase pressure not being sufficient to slow the oil draing back through the holes, it's certainly enough to overcome open breathers and blow oil into jars, and in spite of an open breather, still blow oil out of the rear scroll. I can't see how it can be discounted. It's the reason the breather(s) exists in the first place, and suction was added to increase the breathing ability. It just happens to have added a new problem. Something, call it factor X if you like, enables the timing chain cover to fill with oil, until it completely covers the entry hole to the breather canister. Then the suction pulls it into the inlet. That suction is apparently weaker on a single HIF, than on twin HS2's. I know that because I swapped from twin HS2's when I had oil sucking, to a single HIF and the sucking stopped. Stop all suction and the sucking stops. The trouble is, lower suction or none, means higher crankcase pressure, and leaking through the rear scroll. I'm fortunate if you can call it that, in that I have not one, but two engines in which this has happened. I've stripped one(my spare), and the only anomaly I found was a dodgy cam endplate that leaked oil from the sides. When I strip the 2nd engine(my current in the Sprite), I'll be able to look for the same thing. However, in the 2nd engine, I believe I used a new cam endplate. So it'll be an interesting comparison. The other things they both share are big valve heads, and bored out blocks. Both have standard cams. Both have oil pressure even when hot, of well above 65PSI, AND, both engines sucked oil right after a rebuild. Apart from me :), what else do they have that causes them to suck oil? |
| Lawrence Slater |
| PS Tim you wrote, "Hmm this would mean that using vacuum to reduce scroll seal leaks could increase oil flow into the timing chain cover!" Yup that's what I said a while back too. Crankcase pressure pushing the oil from behind, vacuum pulling the oil from the front. That'll slow down draining and allow the cover to fill. But I don't think that high crankcase pressure, prevents or slows the oil feed from the crank or cam bearings. The oil is driven by pump pressure and my engine oil pressure is well over at least 65pis even when hot, and never below 25/30 when idling. |
| Lawrence Slater |
| Hi Lawrence Thanks for reiterating the history of this. I doubt there has been any other issue with the midgets which remains unsolved despite 30 years of investigation. You have my greatest respect. One thought it had (and you have probably covered this) is whether any of the pro engine rebuilders hat sometimes pop up on here had any experience. Surely if this is partly a new engine phenomenon then they should have seen it on dyno tests? I'm going to trial the pcv and if that doesn't work I am going to use the fuel pipe blanking plate. I really think the vacuum is important and given the "nut and bolt " nature of my rebuild I don't want oil pissing out of the scroll seal all over the underside of the car! Cheers Tim |
| T Dafforn |
| Tim, earlier you listed possible combinations for the breather system. But there are only two basic configurations. Early cars operated a simple "open to atmosphere" breather system which was perfectly compatible with with their lower power and lower engine capacities. Various arrangements open vented the engine cavities to prevent a build up of pressure. Some fed the fumes into the intake system to control engine bay fumes, but there was no positive extraction involved. As power and capacity increased, so did the potential for sufficient piston blow by to build up crankcase pressure and defeat the rear scroll system.Also there was an increasing awareness about environmental issues. So the passive breathing system was upgraded to positive extraction. The positive extraction only takes two forms. Either to the manifold, always controlled by a PCV unit, or the later improved system via a Y branch to the carbs. All other variants are aftermarket or individual's modifications. Tim, if your system connects to the manifold without a PCV to control the excessive suction then it is only a partial system. Its not surprising that it is drawing excess oil fumes. And I would expect that suction to be sufficient, especially on the over-run, to capture and draw oil droplets into the breather orifice, even without Lawrenc'e high oil level scenario. |
| Guy W |
| Lawrence <<---- I've been saying that since last year and long before>> I know you have and I have never denied it! What I have been saying is that there are other, probably more common situations, which also cause a belch of oil smoke so I don't think its a one answer fits all circumstances. As far as I know, my car has never belched oil fumes in the mega style that would indicate a submerged breather orifice. Mine does give an occasional brief oil belch(or did before I added a catch tank)which is short lived, a second or two, and I think was just the clearing of condensed oil within the breather pipe. A one second spit of oil phlegm. Similar, but of a different scale to what you experience, for quite different reasons. One aspect that I don't think you have focussed on is this point I was making about a standing wave of oil. Quite apart from the oil splattering around with the rotating parts, the oil surface won't just rise and fall evenly within the chaincase. The chain will act as a drag on the oil, pulling a "bulge" of oil up on the rising side and probably a corresponding depression of oil on the falling side (where the "overflow" hole is (!) With viscous (cold?) oil this wave differential could be quite substantial so the oil perhaps is dragged high enough to reach and submerge the breather orifice. Add that in to your thoughts and I think it is a more likely explanation than the effect of pressure in the chaincase on the oil flow in or out via the oilways. I think that the window isn't an overflow (as your measurements confirm) but is simply to connect the voids within the engine to prevent different pressures building up. To all practical purposes the window is large enough that there will be no pressure difference between the chaincase and the crankcase. |
| Guy W |
| If you remove the suction completely, cap the breather outlets, remove the oil filler cap and put your hand over the opening on the rocker cover, there will be pressure felt there too, transfered via the push rod holes. If you put a light piece of paper over that opening, it will lift under that pressure. If you try pouring oil into an engine with pressure in the rocker box cover, it will be pushed back somewhat, and you won't be able to pour in the oil as quickly as when there is no pressure, such as when the engine isn't running. -- Ford 1500 engine for example with no vacuum breather, and any other engine with pressure in the rocker box cover. If at the same time you tried to pour oil into the rocker box, you also applied a suction at the rear end of the bottle, (such as squeezing the bottle to squirt the oil in, and then releasing it, which draws the oil back again), that would magnify the effect. The oil flow into the rocker would at least slow down, and at some point cease, and reverse. Engine pressure begins in the crankcase. On a Spridget, if the timing cover chamber was sealed off from the interior of the block, there could be no pressure in the timing cover. But as there are 3 holes, pressure is "transferred" to the timing cover via those 3 holes. The pressure(gasses) are moving from the large interior of the block, to the small interior of the timing cover, just as in the scenario above. Oil draining from the timing cover back into the pressurised block interior, is much the same as pouring oil into the pressurised rocker box cover. With an open breather canister on the timing chain cover, the 2 small drain holes, and the single hole in the block face, are the equivalant of the oil filler hole in the rocker cover. If you were able to place a light seal over those 3 holes, when the engine was running, the seal would be blown out into the timing cover interior, by the crankcase pressure exerted on the other side of the seal. Oil draining back through those holes acts like a light seal. It restricts the attempt to pressurise the timing cover interior, and is likewise resisted by the pressure pushing the other way. The oil is blown back or it's progress is slowed down. All the while, the crankshaft front main bearing, and camshaft front bearing are pumping oil into the timing chain cover. And here we go again on the belch of smoke idea. As I said before countless times, no doubt some goblets of oil do get sucked up by the vacuum. No doubt too, some oil residue gets left in the breather hose, and on the breather mesh. Also no doubt, that some degree of condensed oil mist also gets sucked up and may cause a little smoke. And finally it's reasonable to suppose that a standing wave of oil is dragged up the inside of the timing cover. FORGET THAT. Put it aside. Those things happen in ALL spridget engines. But NOT what I'm talking about. What we are talking about here, is of an ENTIRELY greater magnitude. A full timing chain cover of oil, plus the full breather hose, in a continous column of liquid oil sucked into the engine and the remains squirted out of the exhause and visibly dripping from the tail pipe. I calculated my breather hose alone as containing .185 ltr of oil. Taking into account the oil displaced by the shafts, chain and sprockets, how much does the timing chain cover contain if full of oil? This cannot be caused by mist, droplets, goblets or a partial standing wave of oil. If anyone wants to see exactly what it looks like. Attach the breather hose directly to the manifold ala Tim. The suction must be so great, as to completely overcome the oil draining back into the sump. Do that, and then you'll really know and ignore the other effects that aren't the cause of this problem. The next question is always asked. "Are you saying that if left to continue it would drain the sump?" Nope I'm not. If left to continue, it would go on until the breather entry hole inside the cover was open again. But neither I or anyone else ever lets that happen. We stop the engine. Pity I didn't have a digi cam back in 1980 or 1998, the last time I had it on my engines. Tim, there are quite a few posts about people who've had an engine built "professionally", and have had this problem. Nobody ever resolved it. Some simply got rid of the car, and others got rid of the vacuum on the breathers, preferring instead multiple breathers left open to atmosphere. You asked if this is a partly a new engine phenomenon. No it's not. I was showing this to a Rolls Royce trained mechanic back in 1982/3. He concluded my engine was knackered, or that something was wrong internally. You may or may not have read about my camshaft front bearing being recessed. -- see the other thread -- engine breather-- for a picture (Posted 20 February 2012 at 17:38:15). He thought that wasn't right, but I've since been told it is. I'm still not so sure. Anyway, I know from posts -- other than just mine, back as far as May 2000, that this has been going on, and misunderstood, for a very long time. It's not new at all. But clearly, not everybody has experienced this. So in some special way, not all engines of the same performance spicification, are the same. Something else is going on in these engines. |
| Lawrence Slater |
| Lawrence, I did say I had not experienced this. I did say that a short 1 -2 second belch of smoke can be caused by oil droplets in the breather hose. All this is true. I did also say that this was similar (i.e. oil smoke) but of a different scale to what you experience, and for different reasons. Got that this time? I am agreeing that your oil suction phenomenon is different, a different scale and no doubt caused be different circumstances. Pressure gradients. Of course if you seal up all the openings you can detect and feel the pressure build up whose origin is the piston blow by. So it is significant. There will be a pressure gradient from the source in the crankcase, through to the outside via the breather system. On cars with positive extraction this pressure gradient will be increased by the lowered pressure at the PCV or carbs. But the pressure gradient will be at its greatest where the flow of gasses is restricted through the narrowed pipes. Where there are wide open "windows" between chambers of the engine the pressure will equalise pretty well instantly between those two spaces, but remain very different to the external pressure where the suction from the induction system is being applied. I think the oil wave is significant. Once the rotating chain has lifted this wave up it will remain raised so long as engine revs are maintained. If it is lifted high enough to reach the sucking orifice of the breather system it will provide a continuous supply to that point until the revs drop and the wave subsides. Its an additional and relevant factor. |
| Guy W |
| The standing wave isn't to discount any of your other theorising about the problem. It is just an addition to the process. If there is too much oil in the chaincase then a situation where that oil is raised even higher by the rotating chain simply means that the breather hole gets submerged that bit sooner. Perhaps you are thinking of a wave like a wave on the beach which comes and recedes. Such that it would deliver a dollop of oil to the breather and then subside. That is not what I was describing. I described a standing wave, which does just that. It remains and retains its height in the same place. In this case, so long as the timing chain continues to rotate. |
| Guy W |
| Yup I got all of that Guy. LOL. "Where there are wide open "windows" between chambers of the engine the pressure will equalise pretty well instantly between those two spaces," But there aren't wide open windows. The 2 small drain holes in the front main cap are ALWAYS submerged in oil. Even on my hand cranked engine, -- pics in the other thread -- I was pretty much able to fill those drain holes with oil expelled from the front main bearing. In a running engine, when the thick cold oil level reaches sufficient height, -- aided probably by the wave effect you describe dragging it right over that hole -- it begins to spill into the block face hole, and reduces the size of the opening. Because it's thick and viscous, it lingers there longer than if it was hot and thin. As it rises higher still, the hole size is reduced further. Pressure tries to maintain the hole size, and the only way that can happen, is to blow the oil back into the timing cover. Eventually the oil covers the breather inlet, and suction takes it away. Gradually the oil warms and gets thin enough to pour away more easily via the block face hole and the two lower drain holes. But that doesn't solve the riddle. Just like the pressure in the crankcase, and the strength of the vacuum, the lifting of the oil in the timing cover by the rotating chain is a given, that can't be altered. Those things are there in all the engines to some extent, and since they can't be changed, they're not the X factor that truly causes this. As I said, there are tuned engines with way more power, and thus suction capability than mine ever had, that don't have this problem. So around in a circle again, discussing everything in the other thread that's already been discussed before. What is the X factor, that CAN be rectified or altered, that makes a difference? What that can be altered, will lower the oil level in the timing chain cover? Maybe nothing. But to restrict suction is to increase rear scroll leak, so that's out. An additional breather, at the mechanical fuel pump take off, would in effect provide a counter to the suction from the breather canister. Maybe the two suction points would cancel eachother out -- the same suction split and pulling on opposite sides of the same holes. Maybe that would be just enough to allow the oil to drain just that little bit quicker, and prevent it reaching the critical level. And that will be great as a solution -- if it works. But I still don't think it satisfactorily answers the real question. Why do some engines of same "performance" spec, have this problem and others not? I still think it's primarily an oil (over)feed problem. (you can't have a standing wave of oil, unless the oil is present. And if there's too much oil the wave will be bigger). But excluding a bad cam endplate, I have no real idea how it happens. |
| Lawrence Slater |
| PS. If there's anyone anywhere in the world, a professional engine builder, or expert on the A series engine in particular, whose reading this thread with derisory ammusement, ----- then please lower yourself to my ignorant ammatuer level, and step in and solve the puzzle. Be ever so grateful. LOL. |
| Lawrence Slater |
| Agree all that. (Although I still think the window is high enough and large enough to continue to provide relatively equal pressures between crankcase and chaincase.) But put that aside as it is also common to all engines unless just possibly the "knock out" isn't cleared to the same degree in all cases. So as you have said, that leaves a few engines that perform this trick. Probably very few in the total numbers of BMC engines manufactured, but some at least. I am inclined to think that you got it right first time when you identified the worn / bent cam shaft end plate. That is pumping oil out at 60 - 70 psi which must create quite a flow rate. Could that be the underlying cause that tips the balance? |
| Guy W |
| So if the timing chain cover is being over fed why not simply reduce the size of the feed hole in the cam plate? - and additionally assemble the plate with Stag Wellseal to avoid any additional spillage. I bet the plate hole has remained the same size from the first 803's which had weedy pumps, and may need reducing in line with the increased oil flow we now have. Additionally the width of the Duplex gear and chain setup may force a higher standing wave than was ever the case with the simplex arrangement. |
| F Pollock |
| Hi Fergus. Tim said earlier something about restricting the oil feed, and that sent me thinking exactly the same as you, reduce the size of the hole. But I figured it might be a bit crazy, as it may starve the chain. Now you've thought it too though, I feel more confident. lol. So just how much oil do the chain and sprockets need anyway? Given how long I used to make my exposed Triumph Bonneville drive chain last, with just a few drops of oil from a feeder, it does seem that the chain in an A series engine lives a life of luxury. And if they're over fed, reducing the hole might work. But how to do it. I thought about a gasket under the plate, but that would increase endfloat, and a plate over the top of the hole will interfere with the cam sprocket nose, if it doesn't clear the hole. I think I remember you mentioning about using wellseal in the other thread, but using that -- aside from under the plate -- to partially obstruct the hole sounds a bit iffy. It might come out. So how do you reduce the hole size? Guy, I do still feel pulled towards the cam plate as the solution, but others say they've used new cam endplates, and yet they still have the problem. But I too am coming back to my high oil pressure. Bob had it too. Tim, what's your oil pressure? BTW. I took my pressure relief valve spring out, and had no pressure at all. So I know the bi-pass channels are clear back to the sump. |
| Lawrence Slater |
| Spot of weld in the cam plate and re-drill? Thinking about the cross sectional area of the hole. I guess the flow rate through it will be proportional in some way to the cross section of the hole, so a small reduction in the diameter should produce a significant reduction in flow rate. A fluids engineer would know the formula. That in itself could have side effect (benefits?) in increasing the flow onwards and upwards to the rockers. Given that oil is also spilling out from the front bearing that should still give plenty for chain lubrication. Would reducing the oil flow have an impact on the front cam bearing? I think it would remain well enough lubricated, but what about the other oil function of removing excess heat from a hot spot? I would guess it would still be OK, but it is something worth bearing (!) in mind. I thought on your engine that the problem was excess oiling from the cam plate because it was bowed around the edges and allowed oil to escape around the circumference as well as through the cam plate hole? Also, if the inner face of the camplate is worn and scored, it will allow a continuous flow of oil around and out, rather than just a squirt once every revolution as the delivery holes align. |
| Guy W |
| perhaps the following observation; I did renew the front cam plate when i rebuilt the engine but did not renew the cam bearings. It does seem that excessive oil in the timing cover is the problem. A slightly worn cam bearing coupled with the right viscosity of oil could be enough to cause the problem. I think its all marginal. Since I renewed the oil cap and breather pipe to the carbs the problem has pretty much disappeared. I got a very slight puff when i used the car in April when the weather was cooler but since then all is ok. interestingly i have been rebuilding a spare 1275 and when measuring the cam bearings they were on the edge of tolerance yet it had apparently only covered 50K miles. |
| Bob Beaumont |
| Guy, that's the problem. Yes I found a warped camplate, and gaps under it. But given others good camplates, how can I be sure that I don't have an underlying problem; -- The same problem that causes oil sucking in other engines? Of course I'll put in a new camplate this time, and new bearings too. If at least one other person had reported a used camplate or a deformed one, then I'd say we have an answer. But nobody has, and that makes me doubt my own conclusions. A blob of weld, if I'm careful I suppose is the only answer. But now you've made me wonder about the knock on effects. Would the designers have figured in extra capacity? Would they have tended to be generous with the oil supply to the chain? If anything, partially closing the camplate hole will increase the supply to the front cam bearing, as less escapes into the timing cover and as you say, the rockers will benefit too. Worn bearings. I don't suppose I bothered to measure mine bob. Mine are indeed scored, but were renewed at the time so I would just have assumed them to be right. I've always thought the front bearing was set too far back, but the holes align in the block. I intend to remove it and see if it will fit reversed, but further forwards. However, if it was fitted correctly, and since it was new, it can't have been the cause, because the engine sucked oil the first time it was run in the road outside my house in London. And that's another point I've just recalled. Where I lived was on a hill. I lived on the uphill side. So because the car was always facing uphill when parked, the oil migrated to the rear of the sump. That rules out oil surge or too higher oil level in the sump. -- At least on this engine. What we need is another engine that sucks oil, -- maybe Tim's if it still sucks oil after fitting a PCV or connecting the breather ot the carbs --- to strip and compare components. Luckily i have the engine in my car that used to before the HIF went on. So when I strip that, the first thing I'll look at is the camplate and bearing. |
| Lawrence Slater |
| Hi Lawrence etc.. couple of answers to you questions: 1) oil pressure was around 75-80 psi (I didn't look closely as I only ran the engine for a short time) 2) Hopefully I won't need to take the engine apart once I have the PCV fitted! I am not sure a agree with your comment "An additional breather, at the mechanical fuel pump take off, would in effect provide a counter to the suction from the breather canister. Maybe the two suction points would cancel each other out -- the same suction split and pulling on opposite sides of the same holes." If the vacuum feed is the same to the two sides then the pressure developed in the crankcase will be the same if one or two feeds are used and both feeds will contribute equally. You are right that if the timing chain case is isolated from the crankcase by oil blocking the 2 holes then two vacuum feeds would allow the two (now isolated) chambers to equalise. In essence you are just providing another connection between the two parts of the engine via the vacuum lines which happens to also be connected to the vacuum source. To me, the 100% cure would be to pull the vacuum from somewhere else other than the timing case. Interestingly most triumph engines have vacuum systems connected to the rocker cover (as you mention) as did a ford crossflow I had in the past.. So perhaps the other interesting question is WHY the breather was put where it was? It is inconveniently placed for installation and plumbing. A breather from the rocker cover would have been better and quite cheap to fabricate (although I suppose it could of increased the height of the rocker which would have been tricky). Interestingly last night I was visiting a friend who has a Gilbern with a ital 1275 A-series. He worked in the head office of many of the incarnations of BL/austin/rover as an engineer and a number of members of the team who designed the A-series personally. I asked him about the breather and oil puffing and he hadn't heard of the problem before. Unfortunately he thought that most of the people he knew were no longer with us.. Cheers tim |
| T Dafforn |
| I doubt that in normal practice (and Lawrence's engine may differ !) the chaincase and the cranckase ever become isolated from one another. The "window" is quite high up and quite large, which is why I believe that the pressure is always equalised between the two spaces. The significant pressure gradient is between the chaincase and wherever the suction end of the system is, pcv or carb. I think that the reason for the breather system being on the chaincase was an attempt to design it so as to re-condense oil within the canister where it is cooled by the air flow from the fan. Whether this really works or not I don't know, but it explains both the positioning and also the existence of the canister itself. Otherwise it would work just as well with an ordinary hose connection. Tim, I really don't think from your initial description that your problem is the same as Lawrence describes. Lawrence did say "now it seems one more can be added to my list", but I think that was before you mentioned the missing PCV. Anyway, if this is the case then you shouldn't have to start dismantling that engine! |
| Guy W |
| Guy, I agree, I think having a single carb system with vacuum taken from the inlet without a PCV was a bad thing! Tim |
| T Dafforn |
| Guy, why do you keep saying the hole in the block is quit large? It's only a circle just over 1/2" diameter, and its half the size of the entry hole to the breather. As for Tim's problem, I've said a couple of times, his may not be a problem at all, since he connected directly to the manifold, which obviously wss inviting trouble. True, I think I did add Tims to my list of 20 or so that I know of, but that doesn't affect the existance of the others. Interesting that you too have over 65psi oil pressure. A number of people have proposed high oil pressure as the problem, forcing too much oil from the cam and crankcase bearings. But who knows? I think you misunderstood my comment about split vacuum points. My meaning was that the suction being applied on both sides of the block face, would reduce the suction on the front of the block face if the suction was applied there alone, as it is now, --- irrespective of any crankcase pressure. As for connecting suction the rocker box, that was how the early A series were. The timing cover connection was a later developement. |
| Lawrence Slater |
| Sorry Lawrence, I am not trying to disagree with everything you say! ;-) It is in part the old problem of fully conveying (or reading) what is intended when its done by e-mail or on a forum. When I said the window is quite large, I was relating it to the size of the drainage holes in the bearing. Relative to those, the window hole is quite large. It is ample for equalising pressure between crankcase and chaincase. All 3 of my engines currently have the chaincases on and I don't plan on removing them just to check the hole size. But I think that the front plate hole is around 2" diameter, and behind that sits the recessed hole in the block which is around half that diameter. And as for "Tim's problem" I said that you added to your list BEFORE Tim mentioned the missing PCV. That was in acknowledgment that once you knew of the PCV your advice changed. |
| Guy W |
| No need for sorry at all Guy. I was just wondering why, but asked a bit too bluntly :). And agreed. It's exhausting – and somewhat time consuming -- trying to write full explanations, in order to convey exactly what you mean, and what you are thinking. In a face to face conversation it takes seconds to make a correction, or give clarification, but on line -- at my typing speed -- it takes a lot longer, and once committed to print, well as you say it's the old problem. It's why "I try at least", to be clear in what I write, and don't(often) use abbreviations or acronyms. Actually I quite enjoy trying to get my full meaning across in writing. Good exercise for the brain and improves my writing skills, even if not my two fingered and my right thumb typing skills. :). Ok I see what you mean about the relative sizes of the drain holes and the hole in the block face. Yes definitely. But ----"It is ample for equalising pressure between crankcase and chain case." ------ Perhaps it is ample EVENTUALLY, but NOT in the crucial warm up period, when the oil is thicker, and draining slowly. At that time, with the oil still thicker than when warm, when the oil level reaches that hole, it partially obscures it. Hence in order to maintain equal pressure, the oil has to be blown back out of the way, back into the timing chain cover. BUT another BUT, and this is VERY interesting, and puts your "ample size" comment in a different context. You said --- "But I think that the front plate hole is around 2" diameter, and behind that sits the recessed hole in the block which is around half that diameter." I've since been pondering the size of the hole in the front plate too. Earlier I mentioned it's existence, to justify the existence of the "overflow" hole in earlier engines. But it didn't occur to me at the time to wonder why it was so large relative to the 9/16" hole in MY block face. If your block face holes are circa twice that size, then perhaps that's significant. Fergus already suggested making mine larger. Mine -- is a well formed circle on the front face I can see, but maybe behind, it's a ragged knockout that might have scope to be enlarged. Maybe mine, and maybe some other engines that suffer oil sucking, have small block face holes, and those that don't, have larger ones? |
| Lawrence Slater |
| Lawrence, see my post of: Posted 12 August 2013 at 20:54:58 I thought my use of language might have initiated a response then, but I guess you missed it. Or didn't understand what I was getting at! |
| Guy W |
| Looks like we need to commission a survey of hole diameter! Cheers Tim |
| T Dafforn |
| Yep saw that Guy, and kind of answered it, ignoring the reference to virgins, since it's a long time since I had one. lol. At the time though the relative sizes of the engine plate hole vs the block face hole, hadn't quite triggered a thought process. But now it has, it's a reasonable question to ask, -- why is the engine plate hole so large for such a small block face hole? |
| Lawrence Slater |
| Dunno. Maybe its lighter, 'though this isn't convincing me! |
| Guy W |
| Me neither, lol. Must have been a reason though, even if it was a mistake. |
| Lawrence Slater |
| I wonder if some sort of spring loaded poppet valve fitted to the canister could be devised. It wouldn't solve the cause, but could be arranged to stop the oil column when it starts. The idea is this: Whilst the induction suction is pulling fumes and excess crankcase pressure out, the valve would remain closed and the breather system would work as normal. If, or when, the canister opening begins to suck oil the resistance to suction must increase quite sharply. Under normal conditions it is pulling just gas, or oil filled vapour. Once that is changed to lifting the column of oil the resistance will increase. Arrange the tension on the spring so that the spring in the poppet valve is overcome at the point that increased resistance from the oil being drawn up, the valve will then open and draw air from the outside, allowing the oil column to fall and drain back into the chaincase. |
| Guy W |
| Yup I remember you suggesting that before on the other thread, and it's a good idea if the fault can't be identified and rectified. Do you know if there's an "off the shelf" type of valve that could be adopted for the purpose? LOL. 2 threads at once now, repeating and discussing all the same issues. Madness :). In retrospect, I should never have reactivated "engine breather", but I wanted to keep Tim's thread "clean" as his problem is probably very specific, --- connecting directly to the manifilold without a PCV |
| Lawrence Slater |
| Tim, have you got your head back yet? Are you going to put the PCV on the manifold as standard? It may very well solve your issue entirely. |
| Lawrence Slater |
| Hi Lawrence, With a bit of luck I should get my reconned head back tomorrow so I can fit it over the bank holiday. Was very tempted to fit another head I have just to test the hypothesis but would have been a waste of time as I would have had to take it off to fit the new one.. Cheers tim |
| T Dafforn |
| Right, so have replaced the head on the engine disconnected the breather from the manifold and fired her up. And......, No plumes of smoke! Then connected up the breather via the PCV and still no smoke! So all good. Looks like directly connecting the breather to the manfold is a bad bad thing! |
| T Dafforn |
| Tim Hurrah....Next thing to check is whether your rear crankcase seal is leaking. Tell tale drips on the drive and suitable chastisement from the C in C did it for me... Would also take it for a damn good thrashing to verify everything. |
| Mark O |
| just got to fit: bonnet Passenger seat seatbelts and wire the lights Definitely the home straight though (I hope!) Tim |
| T Dafforn |
| Going back to the original question...Always re-torque the head gasket after it's warmed up, rather than write the head off as cracked, a leaking HG might be because you'll find that the head nuts are only finger tight despite being torqued when the gasket was firt put on there. Regarding breathing, I had oil sucked up through the timing cover as you described, far worse when it was all new. I machined up a nylon 'bung, that sits in the pipe from the timing cover to the y connector on the SUs, this has a 4 mm hole drilled through it, so restricting the amount of air that can be drawn up through it. |
| Robin Cohen |
| Trouble is, restricting the suction defeats the point of having it. |
| Lawrence Slater |
| Although all seems well slightly confused about the action of the PCV. It is one of the ones that looks like a frying pan with one tube being the handle and a second perpendicular to the pan. Initially I attached the inlet manifold to the pipe perpendicular to the pan but I couldn't feel any vacuum from the other pipe. I then swapped the connections an felt the vacuum. Confusion is that this may be the reverse of the way I thought these were attached to the manifolds in other cars. Once all connected up I could feel a good vacuum on the oil filler. Cheers Tim |
| T Dafforn |
| Hmmmm. Looking at http://mgaguru.com/mgtech/engine/cv103.htm It looks like I fitted the valve back to front. Doh! Tim |
| T Dafforn |
| Checked the pcv and it seemed not to function when fitted the correct way round. Took it apart and swapped the orientation of the diaphragm round and Robert's your fathers brother. Tim |
| T Dafforn |
| Phew, thought it was me going mad. I'm in the same boat, engine rebuilt all setup nicely running twin su's and the big K&N filter, y breather connected from the crankcase to the carbs. I also have a tube running from the rocker box to the back plate of the filter. Get five minutes down the road and a plume of smoke from the exhaust. Accelerating makes it worse. Give it a minute and then no smoke. Always seems to happen when the thermostat on the head opens (theory - only mention it as the temp gauge moves). Once it's happened it wont do it again. If I run the engine first on the driveway and let it get warm it will not do it at all. Think I will leave the crankcase open to the atmosphere and see if I get the same. All interesting reading though and this engine did it before the rebuild as well but no one could answer it then either. Regards Shaun |
| Shaun |
| Shaun, as it's not the standard set up do you have a vented or non-vented oil filler cap |
| Nigel Atkins |
| Hi Shaun. Another to add to the list then. Very interesting that is sucked oil before you rebuilt it, and it STILL does it afterwards. That proves an underlying cause. Did you read all the "engine breather" thread? I'm firmly convinced the chain cover overfills and doesn't drain fast enough, --- until the oil gets warm enough and thin enough, to drain faster, and then the sucking stops just as you describe. |
| Lawrence Slater |
| I have a vented filler cap, tempted to put a small filter on the crankcase breather. I recall this was a popular mod back in my mini days. Not sure if my engine is running a duplex timing chain but wonder if that might be the cause of the oil not draining fast enough. Might check with my engine builder. Regards Shaun |
| Shaun |
| What engine is it Shaun? |
| Lawrence Slater |
| It's a 1972 1275 with a +60 overbore making it 1330 now, before the work it was a 1310. Head has been modified and the pistons dished to lower the CR after a block skim. Typically runs about 30 psi at idle and 50 psi when cruising. Mated to the std 4 speed box. Only got about 150 miles since the rebuild planning several 60 mile trips once I have confidence in it. Regards Shaun |
| Shaun |
| Shaun, as your system seems to be a bit of both breather systems (the standard '72 doesn't the rocker cover tubing) I just wondered if you might be better with a non-vented filler cap, if you've got one of these chrome ones with a hole in the top you could just put a bit of blue-tac over the hole to do a test run before putting a filter on the crankcase I'd check with the engine builder and explain to him exact your breather system and carbs and see what he says if you need a vented oil filler cap the £4 black plastic vented and filtered ones are considered better for breathing than the chrome or steel ones with just the hole in the middle  |
| Nigel Atkins |
| Shaun that info about your oil pressure is good, because it probably rules it out as a cause on mine and others, who have the oil sucking, but also have high oil pressure. You don't have "high" oil pressure, but you still have sucking. Both my engines are overbored, but only to 30+ and 20+. What bore was yours prior to the rebuild? Was it standard? Bearing in mind that you said it sucked oil before the rebuild. |
| Lawrence Slater |
| Hi Lawrence The engine had a previous overbore and was removed because the engine had become smokey - worn bores. But it did smoke five minutes down the road before the real problems started. However it wouldn't stop smoking once it had started and the reason for pulling it!!! mm might of rebuilt it for the wrong reasons, better not tell the mrs...... Do I need to be concerned about my oil pressure, I assume it's because the engine has to bed in. Shaun |
| Shaun |
| What does your oil pressure peak at? 30 at idle is ok, and 50 cruising when hot is ok, but what revs is that? For a new build (mains and ends), I would have expected higher. Did you check the oil pump with a feeler gauge, or replace the pump? Nope it won't get higher as the engine beds in. If anything it would get lower. |
| Lawrence Slater |
This thread was discussed between 11/07/2013 and 05/09/2013
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