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MG MGA - Plug colour

The plug on No.2 cylinder is a different colour to the other three. If I swap the plugs and run the car I get the same result on No.2, so it doesn't look like a faulty plug. The engine generally runs very nicely unless I really push it through the gears, when it seems to hold back a little as the revs climb. I have checked the cylinder compressions and they are all 170lb p.s.i. Am I looking at a sticking valve on No.2? I have recently overhauled the engine and fitted a new camshaft and followers. The head was overhauled by a machine shop, they checked the guides, replaced the valves and seats and skimmed it flat. At tickover and mid-range the engine runs perfectly and at 70+ it is smooth and even. See the picture, the left plug is No.2 and the right No.1. Plugs 3 and 4 look exactly the same as No.1.


Lindsay Sampford

Lindsay-
Left (#2) looks about perfect. The other one or three are running a little lean/hot.
If the hesitation is right about mid range, I'd say it's getting too much advance around 3-3500, the usual place. Could be up or down a bit from there. Or it could be a developing high tension fault, since that's where the maximum load on the system happens. Has anything been done to the dist.in recent memory? If you still have points, out of true points cam could account for the difference; if it's really bad, it could still do it with electronic.
It could also be going lean around the same point. Easy enough to richen a flat or two, and see what happens.

FRM
FR Millmore

My original thought was a break down in the plug lead; then I read FRM's post which covers it all. Try swapping a plug lead to establish if it's the distributor or lead.

Steve
Steve Gyles

Thanks for your quick replies and thing to think about! Distributor is about 2 years old but I suppose that doesn't stop it from having a faulty cam! It's not a Chinese one and it has points. HT leads are wire, I have tried swapping the caps, but no change. HT coil is a Lucas sport and I am using NGK B6ES plugs with a 35 thou gap. Ignition timing is 14 degrees dynamic at 700RPM. Engine is a standard 1500.
Lindsay Sampford

Lindsay

If the leads are wire then, presumably, you have suppressed caps. Could one be at fault?

Steve
Steve Gyles

I swapped them Steve, and it made no difference, No. 2 stayed the same. I will, as FRM suggests, richen the mixtures and see what happens, I have got the carbs a bit on the lean side.
Lindsay.
Lindsay Sampford

Just given the car a good 60 mile thrashing having checked the sync and mixtures on the carbs. Engine is smooth as can be at all steady speeds up to 70+, but I get a sort of holding back and a very slight misfire when I accelerate hard and as the revs reach about 3,000. I have checked the plugs again and No.2 is still black whilst the other three are all clean. I have taken another picture of plugs 1 and 2 and I would reckon that my misfire is connected with the state of plug No.2. The blackness doesn't appear to be oil as it is dry and very matt looking and I am not leaving a blue trail of smoke behind me. Cylinder compressions with the engine hot are all the same at 170lb p.s.i. I am at a loss as to why two plugs that share the same carb should look so different. Come on you guys, I've got to nail this one!


Lindsay Sampford

How about the inside of the cap and the connection of no.2 HT lead? Have you tried swapping leads, or just caps? Switch 2 and 4 (they should be similar length) that will also confirm the connection to the cap.
I guess you have already swapped the plugs round.
Neil McGurk

Hi Neil, I've swapped caps and checked the leads for continuity, but there is a new development which points to a distributor fault. I have just been checking the ignition timing on all four leads with my computerised timing light. No.1 is 14 degrees BTDC, No.4 is 12 degrees BTDC, both are rock steady, but No.s 2 and 3 jump about over a range of about 10 degrees. Can't quite figure out why 2 and 3 are so erratic when 1 and 4 are so steady, any ideas anybody?
Lindsay Sampford

Lindsay-
" misfire is connected with the state of plug No.2." I expect it's the other way round - the plug condition is a result of the miss.
"and as the revs reach about 3,000" That is the point of max volumetric efficiency, consequently both the point of max load on the HT system, and "should be" the point of max mechanical advance, hence max sensitivity to too much advance. Either the HT side is breaking down or the scatter is causing too early firing on some cylinder(s), likely the ones showing timing scatter.

Where do you get the 14deg@700 from? Book is static at 7deg. I don't have the curve specs handy, but +7deg @ 700 seems a bit high. OTH, we used to find that 10 static was fine, with better power and mileage.

Mark your pulley for more scale, and check timing on all 4 @ 3000. Try to get a series from 2000-3500, vacuum disconnected.

The timing scatter is characteristic of sticky points, loose breaker plate, and loose/out-of-true dist shaft/cam. Look at the plate configuration in respect to the point loading at the cam and the plug terminals. 1-4 and 2-3 are at right angles to each other, and will set up different but paired forces in the plate mounting. This is a consequence of the non-balanced rotors available now, and the bi symmetrical design of the mech advance system. Weak points spring and/or sticky pivot will aggravate these forces/deflections. The plastic "Quikfit" = quick trouble points are notorious for these problems, esp in the decadent repro versions. Some plastics are known to get sticky or soft when hot. Lubricating the pivot and bending the spring for more tension may fix. Ideally a set of real old time Cooper S points that go on a post are the cure, if you can find the bits.

Set up an indicator to read actual point cam lift in all 4 positions, and move the shaft around to find slop.

Push/pull on the breaker plate to find looseness - I have had cars come in with no screws holding the plate down, and screws too short to reach the threads in the dist body!

.035 plug gap is the upper limit for the 25D cap, and there is little advantage to going over the book .025, except possibly at idle with very lean mixtures. Wide plug gap does push you toward HT problems, and the Sport coil is well capable of jumping an arc all over the place.

Why are you not using projected nose plugs? Far better, N9Y or equivalent.

All that ought to keep you out of the pub!

FRM
FR Millmore

FRM, I have found that 7 degrees static translates to about 12 degrees dynamic at tickover, I gave it the extra 2 degrees to see if it would help with that "holding back" feeling I was getting when I tried to get some revs through the gears; didn't seem to make much difference. I have just fitted a new distributor cap to see if it helps but it is still the same story with the timing light i.e. steady firing point on 1 and 4 and erratic firing point on 2 and 3. As you say, these are diametrically opposite positions on the distributor so I think the next step is to have the distributor off and inspect it closely for the points you mention. I had already gone back to the standard 25 thou gap on the plug points in case that was causing the fault but it is just the same. Incidently, the distributor is a nearly new 25D4 so it could be a manufacturing fault rather than wear.
Lindsay.
Lindsay Sampford

Lindsay-
Your timing setting sounds good. The problem is in the scatter.
So, distributor in hand:
There are two nylon bearing buttons on the breaker plate, creating an axis of movement on which the plate can tilt. There is a formed steel spring which resists the tilt. The cam produces a radial force at the points, but the true radial direction of this is moved in the direction of rotation by the advance of the cam face on the points block. If you consider the resultant force vector, it is directly in line with the axis established, when the points are opening for 1 & 4, and perpendicular to it for 2 & 3. So, any variance caused by the plate will be primarily on 2 & 3. The initial spark for either could be advanced or retarded, depending on what else is sloppy. Rotor imbalance alone (with normal clearances) would cause #2 to be retarded, #3 advanced, BUT, it would also cause the point spring pressure to be high for 3 and low for 2. All this will set up vibrations in the plate, with resulting timing variations. Normally, the point spring pressure and the plate retaining spring pressure will damp these out, but if either is weak, or anything else is sloppy, you will have exactly what you observe. It will probably be worst on 2, since the spring pressure is lowest there.
There is a retaining slotted rivet that limits the amount of movement of the two breaker plate sections relative to each other. On worn plates, I commonly hammer the rivet down so that there is minimum movement, while still leaving it free. Wear here is generally accompanied by wear on the center spigot of the plates, which I have been known to resurface with silver solder; it's easier to replace the plate, if it's not Christmas night or the like!
Generally, if things are not too sloppy, the points spring is strong enough to damp all these random things out. As I said earlier, presently supplied points are frequently not good in this regard, and I routinely bend the spring backward to increase pressure.

FRM
FR Millmore

FRM, I have removed and stripped down the distributor, everything looks good and tight, but there was some serious corrosion on the cam, coincidently on the lobes for 2 and 3. This is despite my greasing it, I guess it's the winter lay-up that causes this sort of thing. The points are the originals that came with the distributor and the heel is made of some sort of fibre/resin material. I am wondering if the drag of this stuff on the rough surface of the cam was enough to retard it slightly and probably intermittantly in opposition to the bob weights. Anyway, it is all cleaned up, greased and oiled and fitted with a new set of points with a plastic heel; probably the sort you don't like! I'm off to bed now (it's 25 to one here), and will re-fit it in the morning and let you know what happens.
Lindsay.
Lindsay Sampford

Distributor re-fitted and not a lot of improvement. Firing point of plugs 1 and 2 is steady, firing point of plug 3 is generally at the correct point but jumps about a bit and plug 2 is slightly late and jumps about a lot. Plug No2 is still running black whilst the other three are clean and I still have a slight misfire at about 3000 rpm. I have also changed the coil but it makes no difference. I feel it must be a faulty distibutor cam but the points gap seems to be the same on all four lobes. Has anyone had trouble with an Indian made 25D4?
Lindsay Sampford

I was going to congratulate you on the rust, since that seemed a good candidate, but you've knocked that down!
What sort of grease do you use? I use Lubriplate, and it can go 20 or more years unused & outside without getting rusty.
So, do what I said and put an indicator on the points cam and measure it, both lift and slop.
Did you increase the spring pressure as I said?
Your present results are in line with what I said about spring pressure variance. Points gap is a static thing, not how it operates at all. The rotating parts can still be wonky, esp Indian ones from what I've seen.
If all this is too difficult, take it to somebody with an engine analyzer or better yet a distributor machine. Get the actual advance curves once you get the thing stabilised enough to read the firing point(s).

c1951, my father was racing flathead Ford V8s in Hawaii. We had a really good car, but every time he got out and started passing people, it would go all screwy, missing and breaking up, usually just about when he got in the lead. There were plenty of cars and engines outside the shop, 20 or 30. People guessed and changed parts for three years. After we came back to the states, the car owner even tried painting it, on the theory that it was too ugly and got embarrassed once it got out front and everyone was watching. Somebody finally figured out that while we had many engines, we had ONE "good" distributor - those cars had front mounted dizzys that usually got busted in even minor crashes, so they were scarce, and the distributors were indestructible other than crashes. The distributor got sent to a guy with a distributor machine, and it turned out to have sticky points once it got hot, which took little time since they are directly behind the radiator. So new points and a general cleaning were what was needed to fix three years of constant frustration and expense. Plenty of people had suggested bad points/dizzy, but those in command "knew" it was good. Moral being "Measure things" and "listen".

FRM
FR Millmore

FRM, I realy thought I was on to something this afternoon when I found quite a bit of up and down movement in the distributor drive spindle so I changed it out with one from a spare engine I have, also used the spare retainer. Much less up and down movement but it made no difference in regard to the faults. I will try the spring tension thing, I haven't done that yet. If it were a sticking valve on No. 2 shouldn't it show up on the compression test? It must be something in that distributor. Incidently, the date code on the distributor seems to be week 44 1995 so the corrosion may have got started before I bought it, it came from Moss UK.
Lindsay Sampford

Lindsay-
It's not the valves, or the HT side, or a broken crank - it's the distributor! At least, the timing scatter is, and that could well account for the plug puzzle. Everything else, like the drive spindle, tends to stabilize once it gets turning.
Is there someone who would trust you with another distributor, preferably one with a known advance curve?

FRM
FR Millmore

I think I'll get my old DM2P4 overhauled!
Lindsay Sampford

Lindsay, I did myself a big favour two years ago when I sorted my 1500. Bought a new elecrtonic distributor from Moss in the States. $ 210 They are well made and have advance curve from '68 B. No more timeing variations.
Total mechanical advance is set at 32%, the initional advance I don't worry about, runs cleanly and returns 35MPG out of the traffic. Your plug gap at 35 is asking a lot from a non ( full ) electronic ignition system.

I'm currently wrestling with my own problem, a 1950 4 cyl. 2.5 lt Riley with all four plugs black as the ace of spades. The engine is good , carbs (SUs ) o/h ed, weak needles, clean all the way up the rev. range, 98 oct unleaded. Maybe I'll just ignore it and retain the few black hairs I have left. Sean
S Sherry

Lindsay
Found this thread most interesting. I was having a similar problem with my Mk2 Coupe with a 25 d Distributor - hesitation at 3000- 3500 revs. (Whilst I am nowhere near as knowledgable as FRM and wouldnt question his advice your second picture of the plugs appears to show the carb is set too rich)- after changing all the ignition servicables the hesitation was still apparant.I eventually came to the conclusion that the Dizzy was well worn and the advance was not correct; and I replaced it with the 123 electronic distributor (version with vacuum.) The difference was noticable with much smoother tickover @750 revs and smooth acceleration right through the rev range. All Plugs an Even beige with darker rims; achieving 30plus MPG on a decent run.
I tried several of the different advance curves and settled on the No.6. It also required carefull setting up of the S Us to get the correct mixture. I also have a Lucas Sports coil and tried the plug gap at 30 but have now gone back to 25.
Very occasionally especially after a long run I get a very slight hesitation @3000 revs, and have found this to be due to the rear Carb being low on dashpot oil ? Why this carb seems to run low on oil is a mystery I havent explored yet!!
My solution is quite an expensive fix but I was toying with going electronic anyway
Regards
Paul
P D Camp

Paul, thanks for your feedback. I'm as certain as I can be that the trouble is with the distributor and I need to either get it sorted or changed so you comments on the 123 system are quite useful. I have several options, I could get my knackered old DM2 serviced, replace the distributor with an electronic job (expensive!), get the 25D4 serviced (probably good money after bad as it is not the proper distributor for an MGA) or try something like pertronix on the 25D4. But before I do any of those I'm going to try FRM's spring tensioning advice!
The two plugs in the picture that you mention are both supplied by the same carb, on the right is No.1 showing about the correct mixture and on the left No.2 which appears rich but is probably suffering from incomplete combustion due to incorrect ignition timing. The misfire I get on accelerating is probably no due to the ignition fault itself but due to the plug fouling when presented with the extra load and the momentary enrichening of the mixture, because once I get up to speed it runs cleanly. Anyway, I'm off to tweek up my contact breaker spring, I'll let you know what effect that has.
Lindsay Sampford

FRM, just tried tensioning the contact breaker spring. I disconnected it from the anchor post and straightened it right out and then carefully re-connected it. The points did feel like they had more pressure on them but sadly it made no difference to the ignition timings on the strobe. Cyls 1 and 4 are steady at 14 and 12 degrees BTDC respectively while cyl 3 varies between 5 and 15 degrees BTDC and cyl 2 varies between 2 and 20 degrees BTDC!
Lindsay.
Lindsay Sampford

hi lindsay
was good to finally meet you down in buckingham the other week.
On the plug colour subject, it may be worth borrowing another distrubutor to swap with yours to compare.
I have fitted the petronix fully electronic unit with their "flamethrower" coil to my 3 bearing mgb engine and i noticed immediately a very much smoother tickover and easier starting. I believe this improvement is mostly due to more accurate timing with no points bounce and no dissy bearing or cam wear to cause problems. The coil has real power as i found recently when a lead fell off the cap and i noticed a very occasional misfire, when i looked under the bonnet there was a 2" gap between cap and connector and the spark was leaping this quite happily.

You may be able to persuade someone let you have a trial run with one of these to see if it fixes the problem for you.
best of luck
colyn
colyn firth

Lindsay

I agree with Colyn about the electronic ignition and coil. I too noticed the differences he highlighted.

I am running one of the Chinese dizzies at the moment so my fully refurbished DM2 complete with Petronix ignition is lying unused in my spares box. The only thing I would say about it is that I am suspicious that the advance springs/weights/mechanical advance are incorrect for our car. I never did get it running right after the 'professional' rebuild!

You are welcome to try out any of the bits if you wish. You could try the electronic ignition or you could put your own weights, springs & advance etc in my DM2 carcass.

Steve
Steve Gyles

I decided to swap my old DM2 40510 for a reconditioned one of the same (122 from MGOC). I was quite exited as I drove home from the shop thinking that I would at last find out what my MGA should really go like. The answer was, much the same as it did before I changed the distributor! The misfire at 3000rpm was still there, although it did seem to improve a bit but then I ran into traffic so was unable to try it again. I have posted a picture of the plugs after the 10 mile run they go 1234 right to left. No.2 is still darker than the others but probably not as bad as it was before the run. Maybe I am being impatient and need to run it some more to see if the plug cleans up, but I'm feeling a bit skeptical about it.


Lindsay Sampford

Lindsay

Lateral thinking cap on here. I bet you have your rear carb air filter on upside down!

Steve
Steve Gyles

Steve, didn't read yor posting before I did mine. That's a very kind offer, thank you, pity I didn't see it before I rushed off to the MGOC! At least I now know I've got the correct distributor and if the fault persists I probably need to look elsewhere for the cause. But what can it be, there's only two valves and a piston left!
Lindsay Sampford

Oil running down a valve guide?
Barney Gaylord

Thought about that Barney, but I get no blue smoke on over-run and the plug is not glazed but dry and sooty. This evening I checked that cylinder with colourtune and it was a nice blue flame with no hint of orange. I was thinking of switching to projected nose plugs to see what they did, what do you think?
Lindsay Sampford

It gets trickier as you eliminate things. Next guess might be a broken piston ring. One broke ring can still give good compression. Broken top ring can cause blow-by and high oil consumption by way of blowing out the draft pipe. Broken oil ring can let enough oil into the cylinder to soot up a spark plug.

Rather than tearing the engine apart too look at rings on that one piston, I think I'd go back to your original setup and run a little lean with three plugs a little hot and no fouling on the fourth one. As long as you're not getting preignition or broken ceramic tips it should be okay. If oil consumption is not too high you might live with it for a long time.
Barney Gaylord

Lindsay

Never too late if you want to try out my electronic ignition. Easy to put in to the post.

I am serious about the rear carb filter box. I have done it and it brings up not dissimilar symptoms. Chatting with Bob West he reckons that about 75% of the cases he investigates with these sort of problems have the box on upside down.

Steve
Steve Gyles

Lindsay, how about the ignition timings for each cylinder with the strobe? Is that problem fixed?
Neil McGurk

Steve, thanks very much for the offer, I may take you up but let me give the car a good try out first. I have ordered some NGK BP6ES plugs as lots of people on here rave about them (at the moment I have B6ES plugs that don't have the extended nose), so I'll see if they improve matters. Filter boxes and gaskets are all the right way round, I think I've got the carbs the right way up!

Neil, I am still seeing the timing jumping about on 2 and 3 (1 and 4 steady) at tickover but they are steady at 1500rpm, so maybe that effect is a red herring. I wonder if gravity is affecting the bob weights at tickover but is overcome by centrifugal force as the revs increase. I am comming to the conclusion that the misfire is due to plug No. 2 fouling rather than ignition timing, but why is the plug fouling. If it were due to the ingress of water on that cylinder I would expect the car to start on three cylinders after several hours at rest, It doesn't. If it were due to oil I would expect to see blue smoke or smell it, I have looked at the top of the piston through the plug hole before starting it but can see nothing there. I have set the ignition timing to the standard 7 degrees static which appears as 12 degrees dynamic, the same as the other distributor and the plugs are gapped at 25 thou with a standard coil.
Lindsay Sampford

Lindsay

Another brainwave. have you checked the drive onto the camshaft for broken/worn teeth? That is one item that is common to all your trials to date.

Steve
Steve Gyles

Nice try steve, I thought it might be the cause when I found some slop in the drive, so I changed it, see posting 05 October 2009 at 18:44:14. Just tried starting the car up to see if it guffed any smoke out as it fired up but it was clean. Prior to this I looked into the plug hole to see if anything was sitting on No.2 piston, but it was dry. I do think, however that the engine responds to the throttle better with its "new" distributor. I'll give it another try on the road tomorrow. I see that someone else on this BBS had exactly the same trouble, same plug, back in 2003. No mention of a cure though! Maybe I need to do the same as all you other guys and stick an MGB engine in it!
Lindsay Sampford

has anyone suggested a compression test of all cylinders? With the engine running listen to the fuel pump and check that its not running unusually fast.
J H Cole

J H Cole, first thing I checked, see my original post.
Lindsay Sampford

Sorry LS came a little late to this one and rushed in.
J H Cole

Lindsay, I'm not far away depending on where in Cambidgeshire you are. Let me know if you want to try swapping any parts over to eliminate items.

Regards...JB
John Bray

John, I'm in Burwell, 10 miles north east of Cambridge.
Lindsay Sampford

Lindsay I may have missed it but at no time did I see you mention trying the total advance. Static + mechanical with vacuum disconnected. Run the engine at 3000+ revs and set the advance to 32*. 95% of B series engines like 32*. It sounds to me its about the one thing you have not tried and one of the most likely problems. As for the uneven color of the plugs remember these engines have Siamese ports and poor running could effect cylinders differently. I feel the engine could be retarded up where it counts. Its always best to set the total advance on these engines and let the rest take care of itself. Thats where the engine is working.
Denis
Denis4

You're right Denis, it's a thing I need to look at again. Way back before this thread I tried setting the ignition as you describe. I was finding that the engine hit a wall at about 3000rpm and just didn't want to go through it. The previous owner of the car had rebored the engine but had only done about 300 miles in three years so it had never really run-in (in those years the cylinder walls had picked up some "rust stains") so I wondered if the reluctance to rev was due to it being tight. When I set the ignition at, I think, 34 degrees full advance, it wasn't nice at all, particularly when hot, so I set it back to 14 degrees at tickover which equated to about 10 degrees static. At this setting the engine seemed much happier. But I have done a lot to it since then and over 4000 miles, so maybe it's time to visit that area again.
There are some new developments this morning. With the new distributor the response low down is better than with the 25D4 but there was still a misfire at around 3000. I had a set of NGK B6ES plugs fitted, so to prove that it was nothing to do with one of them failing, I fitted a set of Champion N5s'. It ran appallingly! It felt like it had a rev limiter fitted. The engine would reach about 2750 and would NOT rev any higher. When I got home, I fitted a new set of NGK BP6ES plugs and the improvement, even over the B6ESs' is phenominal! Now all I have is a slight hesitation at about 3000 and then it clears and carries on. I have posted a picture of the plugs after about 8 miles of running (they number 1-4 right to left), number 2 has a little soot round the insulation but it stops short of the centre electrode at the moment (it will be interesting to see if a few more miles blackens it all the way), but I think it is safe to say that the hesitation is not due to a fouling plug. The fact that one plug is running differently to the other three remains a mystery; to me anyway! But is it the indicator of anything significant?


Lindsay Sampford

Another potential problem, as the engine was recently rebuilt is the crank to cam alignment, maybe a tooth out?. What cam is fitted? and what about the condition of the lobes particularly on no.2? I am assuming you have checked and double checked the valve to rocker clearances, but the camshaft has not been mentioned yet has it?
Neil McGurk

Lindsay

My refurbished Distributor came back from the refurbisher with the wrong mechanical cam plate advance. It was a 7 degree cam,therefore giving only (7 x 2) + static advance (7 degrees) = 21 degrees total mechanical advance. The engine would only rev to about 3000rpm. If I dynamically set it to 32 degrees I could not subsequently start the car because the static was now at 18 degrees. I had to file the cam until it was about 12 degrees.

I would be interested to know what cam you had in your old distributor.

For those who may not know what 'cam plate' I am talking about, see image. You can see the advance stamped on it

Steve



Steve Gyles

I had the engine right down myself Neil. Having found several things on the car I wasn't happy with, I wanted so see exactly what was in there. I'm glad I did, apart from anything else, the camshaft and followers were shot! I have replaced both these with the correct new items, and timed the cam with the marks and checked it by the valve clearance method. So it should be right. I've been over the running clearances several times since the rebuild and they have settled and are constant now. I did wonder about the rocker breather to the front air filter. If I run my hand under the front filter I generally find a drop of oil there, but how could that affect No.2 and not N0.1? plus, the deposit on the plug is definitely sooty and not oily.
Lindsay Sampford

Steve, mine's a DM2, it's not like that.
Lindsay Sampford

Sorry steve, didn't read your posting properly. The 25D has a 12 degree plate.
Lindsay Sampford

Lindsay When I mentioned the Siamese ports I was aiming at the fact that number one plug fires straight after number two meaning that number two can rob number one cylinder as it follows that number one intake charge quickly follows number two through the same port and that can cause uneven conditions in these cylinders. Number four follows number three but you say the breather is hooked to the front carby. Try running your breather to atmosphere for a while and see if that makes any difference to your plug colour. Also I have found over the years that a combination of SU carbs and slightly retarded ignition tend to cause a flat spot mid range.
Denis
Denis4

That is very interesting Denis and I wonder if that's the answer. If you look in the archive you will find a posting dated 21st April 2003 called "#2 cylinder fouling". It describes exactly what I have got and asks if ayone else has noticed this phenomenon; according to that posting, no one has! But I think you have probably hit the nail on the head, maybe No.2 cylinder is different, it is certainly the only cylinder to follow another sharing the same inlet port. I think I should ignore it and concentrate on the misfire, which has become a mere flat-spot since changing the distributor and fitting extended nose plugs. It would be nice if other owners of 1500s could have a look and see if No.2 plug appears to run richer than No.1.
Lindsay Sampford

I've got that wrong! 1 follows 2 and 4 follows 3, so is 2 unique? I don't know, now I'm confused!
Lindsay Sampford

Lindsay on your post of the third you say the breather goes to the front carb. Try it disconnected.
Denis
Denis4

FIXED IT! well almost! I finally got a good re-conditioned DM2 distributor that does everything it should from MGOC, the first one had some kind of fault in the advance unit that allowed it to advance without limit. Anyway, having fitted it, I was a bit disappointed to find that sooty No.2 plug fault and misfire was still there, and on top of that, I was dropping more and more oil each time I drove it. This led me to think that it might be some sort of blow-by fault on No.2 although the black on the plug didn't look like oil. I re-checked the compressions, all OK. I then decided to check the front carb air filter, half of it was soaked in oil, that's OK you might say, but on checking the archives I discovered that the air filter elements fitted to my car don't fit the description of the standard MGA air filter "screens" that others have. Mine are "heavy-duty" felt jobs, and when I oiled them, as described in the manual, the engine had great difficulty in breathing, so I had left them dry. The front one had obviously drawn some oil mist from the rocker (valve) cover, so I ran the engine with the pipe diconnected and checked for blow-by gasses and oil mist from the rocker cover pipe, nothing! To cut a long and tedious story short, I washed the oil out of the filter, left the breather pipe disconnected from the air filter with a piece of foam covering its open end by way of a temporary filter, and took the car for a 40 mile blast. Result, ALL the plugs clean after the run, no mis-fire on accelerating and no oil on the makeshift rocker cover pipe "filter". It appears to me that the cause of all my troubles could be these filters; I think someone said they were Chinese. I reckon they are so restrictive that they cause the front carb to suck oil from the rocker cover breather pipe and, having done that, the front filter becomes even more resrictive with the oil soaking. This must be compromising the engine breathing system too; the vacuum generated by the tappet chest draft tube has to draw air in through an oil-soaked air filter, it might be making my oil leaks worse. I have ordered some K&N filters to replace the felt elements, so hopefully that will solve the problem once and for all. But I still can't understand why No.1 wasn't running rich like No.2 when they share the same carb and filter.
Lindsay Sampford

Lindsay

Yes, I recall now that I had something very similar when I rebuilt my car 12 years ago. The new filter boxes came with crap filters as you describe. They were just bits of felt attached to a mesh. The car always ran rich and I could not weaken them sufficiently. Problem was cured when I fitted the K&Ns. Well solved.

Steve
Steve Gyles

LINDSEY, MAY ALL YOUR TROUBLES BE LITTLE ONES, PLEASED TO HEAR YOU FOUND THE PROBLEM. FROM YOUR EXPERIENCE I THINK I HAVE ALSO FOUND THE BLACK PLUG PROBLEM WITH MY OTHER( SU )CAR RILEY 2.5, - AFTER MARKET FILTERS WHICH I OILED AND SHOULD N'T HAVE.

ps HAVE YOU CONSIDERED A BRAND NEW ELECTRONIC DISTRIBUTORS FROM MOSS IN THE STATES? SEAN MGA 1500
S Sherry

Sean, are you trying to get me into trouble with my wife! She thinks I've spent too much on it already!
I soon found out that it was not a good idea to oil those felt filters when I first got the car, but the front filter continued to oil itself. When I rebuilt the engine earlier this year, I thought it would cure the oily filter problem, but obviously it didn't and it does, at the moment, seem like it could be the filters themselves that are at fault, I hope so!
Did you find that it was just one plug that fouled up? That's what threw me down the route of it being either something to do with that individual cylinder or that lobe or position of the distributor. As I said in a previous post, someone else had exactly these same symptoms in a posting back in April 2003, but there was no resolution to the problem posted, I wonder if he ever fixed it?
I think it is so important that when problems are solved and sorted, a posting to that effect is added to the thread. It makes the archive a realy useful resource when you can scan down and see what the guy did to fix the problem, but when you can't, it's a bit like reading a novel with the last couple of pages missing!
Lindsay Sampford

Well done Lindsay, sounds like you cracked it! Must seem like a different car.
Neil McGurk

Lindsay/Steve

Do K&N filters go inside the exsiting MGA filter housing and who markets them?

Regards...JB
John Bray

John

Yes, mine did. Tight fit with the metal mesh band round it. I had to carve a groove into the filter of the front one to accommodate the breather pipe where it sits prod in the metal outer casing.

Steve
Steve Gyles

JB - Barney's got a good section on putting K&N filters into the Vokes air cleaner. I changed to K&N a few years ago after I noticed that the engine breathing through the old felt filters was a little asthmatic. After changing the plugs immediately went white showing that there was a large increase in air supply and the jets had to be richened up accordingly.
J H Cole

Neil, acceleration is better, sound is better and that awful misfire has gone. Gone too is the odd wheezing noise I used to get when I came off the gas between gearchanges; sounded like it was gasping for air, which it probably was! It should be even better when I get the K&Ns fitted (still got the felts in at the moment) from the comments I've seen on previous postings.
Lindsay Sampford

John (Bray),
I'm getting my K&Ns from Moss Motors USA. They do a kit that fits the Volkes cans ($69.95). Moss UK sell individual replacement K&N filters for 33.95. It's a toss up as to which will cost the more once shipping etc is added. Lindsay.
Lindsay Sampford

John and Lindsay

They are available from Bob West and K&N UK in Warrington. Part number E9143

http://www.knfilters.com/search/product.aspx?Prod=E-9143

Steve
Steve Gyles

Linsley, I,'VE just pulled no 1 & 2 plugs from my A 1500 which runs on rich needles, both have light grey electrodes & insulators , with a sooty ring round the outside edge of the plug body,( cooled by the head.) MY TWO BOBS WORTH IS WITH BARNEY, OIL FUMES IN THE CRANK CASE BEING DRAWN INTO THE FIRST CAB OFF THE RANK NO. 2 IF THE MOTOR IS OK,
I WONDER IF YOUR DRAFT TUBE IS PULLING ITS' WEIGHT, DAMAGED AT THE END PERHAPS. YOU ARE SPOT ON ABOUT THE FORUM LINDSEY,WE ALL NEED HELP FROM TIME TO TIME AND AS AN OLD BUSINESS associate TOLD ME ONCE IN THE STATES, NOBODY HAS A MONOPALY ON BRAINS CHEERS SEAN
S Sherry

Steve, that's a different part No. to the one that Barney gives, no wonder my search came up with nothing! I found the site you get when you hit the "Buy Now" button but it only came up with dealers in the USA. Spent some time trawling for the things but to no avail; ended up at Moss Motors!
Lindsay Sampford

Sean, draft tube is fine and clear so I'm pretty sure that once the air filters are sorted everything will be OK. Everything else about the engine seems OK (other than a few drops of oil!) i.e. good compressions all round and no heavy breathing.
Lindsay Sampford

Lindsay

I keep all my receipts and that was the number Bob listed in August 2001. They are not cheap. I paid 23 + vat each, plus postage. Only a couple of pounds change from 60.

Steve
Steve Gyles

Just did a very quick search and came up with the following.

"Steve's" part number E-9143(I have these in mine with the "notch" - they are probably over fifteen years old), 56.55 for a pair delivered:

http://knshop.co.uk/index.php?act=viewProd&productId=2977

Barney's recommendation E-3180, which I think the is a better fit and also a bit cheaper , 53.74 for a pair delivered (probably because it fits Triumph Herald, otherwise 58.73 from the above company):

http://www.fasterfilters.co.uk/airfiltertriumph.html

Neil McGurk

Brown & Gammons sell complete K & N Filters that are a bolt on fit for the MGA
I bought mine last year and just transferred the Adaptor for the Rocker breather to the front Fiter as per Barneys site.
The Price for two complete with cases was around 80
Paul
P D Camp

K&Ns installed and it's a different car! Acceleration is much better and is accompanied by a lovely growl in place of the grumble I had before. What a lot of trouble I could have saved myself if I had realized that my air filter weren't up to the job earlier. I have posted a picture of one of the culprits to help anyone else who's MGA is not running the way it should!


Lindsay Sampford

Lindsay

That's them. Identical to the ones I replaced about 5 years ago.

I bought my filter boxes, installed with the culprits, at Beauleigh autojumble in 1997 at I think it was the Brown & Gammons tent.

Steve
Steve Gyles

This thread was discussed between 22/09/2009 and 27/10/2009

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