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MG MGB GT V8 Factory Originals Technical - Tapping sound from engine
got a problem with my Range rover engined MGB.
As the engine warms up a tapping sound starts and gradually gets louder. Sounds a bit like a tappet noise from the old bucket and shim type
Being hydraulic tappets I thought they if anything they got quieter as they warmed?
The tapping is hard to pin point but it is defintely coming from the left hand bank of cylinders
Any ideas for a way of checking.
If i remove the valley gasket how would I know which tappet it was if it is a tappet.
I have just fitted a new cam and tappets supplied by Rimmers and the engine was Ok for the first few hours
Any ideas gratefully received
If it is a lifter/tappet then by taking the valve cover off and using a longish screwdriver placed on the rocker pillar bolts as a stethoscope you should be able to tell whether it's a lifter or something more serious.
Tapping when hot can also be a symptom of insufficient lifter preload.
Did you break in the cam as per the recommended procedure and use the correct cam lube, otherwise you cam will be wrecked within the first few hundred miles?
Was the engine fully rebuilt and what spec, what oil pressure do you have at hot idle and 3000 RPM?
By the way for future parts purchases you can buy stuff a lot cheaper from other sources than Rimmers.
|I just fitted the cam and followers and they fitted smoothly - what is the break in procedure?|
What is lifter pre load and how do I adjust or check it?
The engine is standard
Oil pressure is about 50psi as I have a high pressure pump
Which other sources are cheaper than Rimmers?
|I've had this for years, factory V8. Coming from the right bank on mine, near the top of the engine towards the front. Wondered if it might be little ends but that was roundly pooh-poohed, although no one could say for sure what it was. Had the rocker covers off several times and used a screwdriver, but whilst the noise is slightly louder towards the ones at front right the difference to others is marginal. I also forced a 10 thou feeler between each rocker and valve when the engine was running, with absolutely no change in noise either inserting or removing. Changed the cam and hydraulic followers (around 80k after the previous change by a PO), couldn't tell how much the cam had worn but the followers had only dished by about a thou. On the restart I was gutted to have the tapping start as it warmed up *exactly* as it always had done. I have found that if I undertake a long trip of 100 miles or more then the noise will have stopped, and stay stopped for several shorter journeys, then gradually come back again. It also goes or greatly reduces if I put the engine under load, and the sound will change with just minute changes of throttle. It all points to something close to the combustion chambers. After 200k on the clock and the original engine and about 100k after the previous rebuild by a PO I decided I should check the bottom-end bearings. To my amazement I found the shells were all standard sizes i.e. it was the original unreground crank (just possibly a replacement I suppose) and all the clearances were just inside the tolerance and in very good condition. Bound to have been replacement shells at some time, but still pretty good going. But during reassembly I suddenly noticed that all the right-bank con-rods are the wrong way round! The machining of the big-ends is asymetric and each con-ron of a pair is turned the opposite way round so the little end sits in the middle of the gudgeon pin on all the pistons. On mine the little end is offset right to one end of the gudgeon pin on the whole of the right bank. I haven't done anything about it yet - just carried on reassembling and using the car based on the assumption that if it hasn't gone bang in the previous 100k of none too gentle miles it isn't going to any time soon. I needed to do the investigation to see what shells to order, and if I had turned those con-rods round I would have needed new shells there and then. So I've decided to leave it be until I have to do the clutch (also getting on for 100k and counting) then while the engine is out remove the crank and turn those pistons round as part of reshelling. Was I right at the very beginning about it being little ends? Time may tell.|
If you have got the engine running after a cam and follower change then there is no point worrying about pre-load now. It should have been measured with empty followers, depressing them for maximum clearance. I've seen figures of 20-60 thou bandied about, but mine were 110-120 on the right and 40-110 on the left. Spoke to several people, one of whom quoted 20-60 on their web site but on the phone said "you wouldn't want to go as low as 20 and 120 should be fine" and others said that for a standard engine my results were fine, you might want to get them more balanced on a highly tuned engine. The whole point of hydraulic followers is to cope with a wide range of clearances, and I really cannot see the point of fitting solid lifters and adjustable push-rods on the V8, when people talk about changing to fixed rockers/pushrods and hydraulic followers on the 4-cylinder!
People talk about cam lube 'for that important first few seconds' but none came with my cam. The beauty of the V8 is that you can put a drill on the oil pump and get it up to full pressure i.e. oil through all the passageways and round all the bearings before you start it. This also meant that my lifters seemed to be fully charged with oil when I *did* first start it as they made no noise at all, unlike after I had done a full set of wet and dry compression readings and all the cranking had emptied them, and it sounded like the engine from hell for several seconds on the first start after that.
We recently had a pretty good discussion on measuring and adjusting lifter preload on the Buick/Rover V8 here:
|Just to answer Steve's question about camshaft break-in procedure, I was advised by many different sources to smear special cam lube on the lobes and then immediately upon first start-up, to run the engine for 20 minutes or so at 2000-2500 rpm, varying the revs a little and definitely not letting it idle. Real Steel, who sold me my camshaft, told me it would not be guaranteed if I didn't do this.|
Mike is correct and that is the procedure for bedding in a new cam, but as you have fitted a standard cam with relatively low lift and valve spring pressures it may not be so critical.
For parts for your V8, Land rover agents are a good source of reasonable price parts and some of the specialists offer good value as well such as;
V8 Tuner. Paul
RPI, although they will try and sell you their complete stock
JRV8 who are in Belfast but offer fantastic service and Jim's a great and helpful guy to talk to.
They all have web sites.
For any tech advice re the Rover V8 for either general maintenance or building a full race engine have a look at;
The V8 Forum.
|Thanks to all for the information.|
I am going to try and locate the sound with the screw driver idea and hopefully find it is only a tappet.
It is quiet if the engine is run at higher revs (or is it just that it repeats so fast I cannot hear it)
Will definitely shop around in the future, Rimmers are just around the corner for me hence I used them.
will let you know what I find
I would only use Rimmers if I couldn't get a part elseware,
Rimmers price for 3.9 cam £185.00
You can order by phone and they will normally get parts off to you the same day, and you mcan get good advice from Paul.
I have fitted another full set of new tappets and followed the preload setup.
the damn thing is still tapping. Quiet until about a 1/4 on the temp guage and then gradually gets loader.
Any other ideas please.
After hearing the tappets tap while filling with oil for a second or so I can say the tapping sound is more solid and louder
I have read about liners coming loose? could this be a loose liner or maybe a little end?
If it is a little end can you get the piston out without removing the engine?
It sounds to be either 3 or 5 cylinder
compressions are all around 200psi
Would it be ok to run it for now to see the season out?
I know things are upside down here from where you live but it sort of sounds like a big end bearing noise to me.
While the oil is cold and thick it will mask the sound of a worn bigend bearing but as the oil warms up the cushioning effect of thick oil is lost to some degree and then it rattles. You mention it is around the 3--5 area. Try pulling the plug leeds off one at a time and see if the noise can be stopped by doing this. If it can be stopped by pulling a plug leed off it is going to be a bigend for sure and you will know which one. Sorry Willy
|Still sounds just like mine, which isn't tappets/cam or big-ends. What happens if you load up the engine? If it gets quieter it definitely isn't big-ends, which in my experience make *more* noise when loaded and only when the oil is fully up to temperature unless they are really really bad. Highly unlikely to be slipping liners, they *should* be sandwiched between lugs at the bottom of the casting and the head, the tops being machined flush with the top of the block. But you aren't going to know for sure unless you remove both the sump and the heads and look for gaps one end or the other.|
You can remove the pistons with the engine in-situ by removing sump and heads. But I'd remove the sump first and have a look at the orientation of the con-rods, as having done pretty-well everything else I'm pretty sure my noise is caused by that and the offset of the little-end on the gudgeon pin. While the sump is off you can check the clearances on all the main and big-end journals except the back one (only undo one at a time) with Plastigauge. Only then remove the heads if you really want to remove the pistons and investigate the little-ends. If you find the con-rods reversed and plan to correct them you will have to replace the big-end shells, they will need ordering, so unless you already know what they are i.e. standards or undersize i.e. it has had a crank regrind you would have to do that first anyway.
If it *is* the same as mine then it's been like it for around 100k and making the noise for probably half that, so isn't likely to go bang any time soon which is why I've put mine back together as-is and will continue to drive it with gusto until the engine has to come out e.g. for a clutch change, but that has to be your decision.
How did you measure the preload and what clearance figures did you get?
I think a small end is most unlikely and a cracked bore and slipped liner on a 3.9 engine would be unusual unless the engine has at some time suffered a total loss of coolant and not been noticed until too late, how someome would not notice is beyond me but it does happen.
Just for the record Paul, you can get a small knock if the bore behind the liner has cracked, as the liner does slip down by up to 2mm and can then move up and down and I have actually seen this,it is more common on the later 4.0 and 4.6 engines.
Steve did you just buy the engine as a s/h lump and fit as is or was any rebuilding checking done?
The rover V8 is generally good for a 100.000 miles before a rebuild is necessary and bore wear is usually minimal and also the cranks can show very little wear provided the engine has had a reasonable service procedure.
The cams are usually clapped by around 70K and the cam bearings should have been replaced.
Sorry not to be able to pinpoint your problem as there are unknows as to the level of wear in the bottom end, if you can clarify what work was done prior to fitment that would help.
|My engine has done 65000 miles and I fitted new camshaft, tappets and timing chain. Everything else is as original and unchecked.|
Good news i have at last found the tapping. After swapping the rocker shafts over the tapping moved to the other bank so it must be a rocker? They look OK though?
The engine does smoke on startup if stood for 20 minutes hot and then restarted so something is worn.
There was quite a lot of carbon around the rockers when I removed the rockers to change the cam etc I was hoping this was because the breather was blocked
I think i will probably end up rebuild another engine and swap thru winter - not an option i really want though as not an easy change
thanks for all the suggestions
Well I would say thats good news compared with a badly worn bottom end.
Give the rockers and shafts a really good clean and then check the cups into which the pushrods fit as that is a common wear area especially if the engine did not have regular oil changes.
Also check the fit of the rockers on the shaft, easier to do this with the rockers sitting in there operating position, as that is where the wear in the shafts will be, if there is not excessive movement then in the short term you may get away with just replacing any badly worn ones and your knock should disappear.
That is fairly good news- These engines are a bit prone to wearing the rocker shafts if the oil hasn't been changed regularly so a pair of shafts will most likely be all you will need. I'm still sooking that my bigend bearing theory got blown out of the water but i'm happy for you that it ended up a lesser rockergear problem. I think I will stop trying to diagnose on the net where the touchy-feely can't happen--maybee Cheers Willy
|These engines have also been known to start lifting a liner!! It taps on the cylinder head1 More serious.|
|Having looked at a couple of blocks these liners should be sandwiched between lugs at the bottom and the gasket and head at the top, so I don't see how they can move.|
|The smaller bore ones don't Paul, that's why many engine builders put "top hat" liners in. This also solves the, surprisingly frequent, problem of small cracks in the block around the liners, which causes water ingress in to the combustion chambers. The increased section at the top of liner means that the liner seals against the gasket and head.|
|So are you saying the top of the liner should be below the top of the block? None of mine were, and neither are they on another 3.5 (non MGB) block I have, and both have the lugs at the bottom.|
|Here is a photo of the block of my 3.9 litre. As you can plainly see the liners are flush with the top deck and couldn't possibly move upwards once the head is clamped down.|
|Paul, that is NOT what I'm saying...........did I lapse into another language? I am passing on information from a very reputable Rover V8 engine builder, that on some applications the liner is NOT clamped by the head, hence the use of TOP HAT liners. Accept it or ignore it as you wish.|
|There is no need for sarcasm. You said "These engines have also been known to start lifting a liner!!". Based on the two blocks I have I don't see how that is possible, as the top of the liner is flush with the deck and the bottom flush with a lug in the casting, see attached photo. |
You went on to say "The smaller bore ones don't Paul". Both mine are 3.5 blocks and as far as I know that is the smallest. You have now reduced that to "some applications"!
If anything, I can see *overbored* blocks would need stepped liners, if the borer cut right through the bottom lug. But surely the sensible thing to do is stop short of that, press the liner in down to that, then machine it flush with the deck.
What actually happens is when the tension is lost by cracking behind the liner the liner can sink in the bore and I have seen evidence of this, and then the liner can move up and down.
Extremely rare on a 3.5, does happen with 3.9 & 4.2 but not that common and then we have the late blocks which have suffered in quite high percentages caused in my opinion by being run at higher temps and lean mixture at high load for emission reasons.
As of last week V8 Developments had 17 4.0/4.6 blocks in for top hat re-linering and would you believe it two of the new Coscast blocks.
|Thanks Kevin, that makes sense to me, I had obviously got hold of the wrong end of the information passed over to me. I'm re-building a 3.9 next week, so I can have a good look!|
If you are in need of any tech or tuning information and sources of parts, log on to the V8 Forum which is 90% Rover V8 and you will get good advice.
|The above recommendation was not meant to imply that good advice is not offered on this forum as this is not the case, but sadly this particular section is only a shadow of it's former self and the forum I recommended has more specific rover information available.|
I did a bit more research the other day and had it confirmed about the "sinking" liners, which explains it all really. Also that the pistons will then lift the liner to produce the tapping and also that the cracking also allows water into the bore. The top-hat liners obviously cure both problems. Thanks for the link.
The people who do top hat linering correctly machine the block so that the top hat section sits approx 2 thou. proud of ther deck faces which then seals to the fire ring of the gasket and has a similar effect to O ringing.
V8 Developments claim never to have had a failure from the large amount of blocks they have done and also Turner Engineering have a good reputation for doing it right.
Also don't believe everything you might read on the RPI site.
A visual check will normally tell you if a block has a problem,you can see if a liner has sunk and if coolant has got into a cylinder there will be evidence of steam cleaning of the piston and and combustion chamber of any effected cylinders.
A pressure test might be advisable for any engine that is going to be highly modified.
I have more information about liner lifting. I've just picked up a 3.9 engine from Chesman Eng in Coventry. They must have had 20+ Rover V8 blocks in for remedial work, mostly cracked to some degree and having stepped liners inserted. They can attest to the phenominon of liner lift!
Point 1. The "step" in the block at the bottom of each bore is by no means a given. The block I picked up didn't, (never), had one, AND they vary in their size.
Point 2. As you so correctly pointed out, the liner does/can, "sink" in the block, caused when the surrounding alloy loses it's "tension" through cracks. These cracks cause an uneven pressure on the liner which pushes it ever so slightly oval, which then causes the piston to "pick up" the liner, and move it.
Point 3. If the step at the bore base does exist, it is often so small as to be cracked off if the piston does "pick up".
Point 4. The different coefficient of expansion of the block and liner can cause the liner to "creep" down the block, especially if "tension" is lost through cracking, then if the piston does "pick up" it lifts the liner the few thou to cause the tapping sound.
Point 5. Chesman offer a service called "ceramicing" for heads and blocks which may have slight cracking or are porous. It involves injecting, under pressure and heated up, a ceramic slurry which migrates to cracks and pores, filling them with a flexible but very tenacious ceramic material which is solid at operating temps. According to then, in 12 years they have never had a failure/return! Worth knowing!
Thanks for posting that information, I have heard of people using the Ceramic crack sealer as a fix for cracked blocks and one guy reported that it cured the problem on a 4.6 engine do for £30 off e-bay a cheap fix.
Apparently you just drain the cooling system, flsusk out to remove all anti freeze, pour in the sealer and fill with clean water and just drive the car for 2-3 days, then drain it out and refill with a proper coolant/anti freeze mix. Probably not as good as chesmans process but did the job.
If your using Chesman for your engine work you are using one of the best in the country, they also do a lot of headwork for some of the well known Rover V8 engine tuners and sell the products as their own.
|The heads are indeed beautiful, will keep you posted on their beneficial beauty!!!|
This thread was discussed between 06/08/2009 and 19/09/2009
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