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Triumph TR6 - Unstable valve ajustment or faulty cam?

Hello,


I own a 1975 TR6 for many years and a new problem occured. I have an head rebuilt and replaced valve springs at the same time. For one valve it was extremly noisy at idle, I checked valve lash and it seems OK. But if I adjusted that valve with engine running, gap was far too wide and after a while the noisy sound reappered. Valve adjustment scew is not faulty?
Is it at cam level that this problem originate.

Many thanks, JGCatford
Jean G. Catford

Hi Jean

Rocker shaft? Rocker arms? Did you replace these items known for wear. Did whoever did the head rebuild check valve springs for height? When it was reassembled were the same valve lifter cam followers used? If they were not replaced they have to be reassembled in the exact same order they came out or the cam lobes will wear very fast and be damaged.

Bill
Bill Brayford

Hi Bill,


I replaced rockers(tappets) and rocker shaft( with hi-resistant type from TRF) and fitted back cam followers at the smae place. May be cam is damaged by some unexplained reasons. Valve springs are brand new but I did not checked heights.
The problems is to find what is not functionning properly...

Cheers, JGCatford
Jean G. Catford

Jean - S'il y a un bruit parce que le gap est trop important, c'est pas grave. Le moteur vas marcher quant meme avec up peu de "valve clatter". Je ne pense pas qu'il y a de dommage dans le "cam-shaft" s'il marchait correctement avant. C'est possible que les ressorts ne sont pas les memes forces qu'avant.

If there is a noise because the gap is too large, it's not important. The engine will work anyway with a bit of valve clatter. I don't think that there is any damage to your cam if it was working OK before. It's possible that the new springs are not as strong as the original springs.

Bonne chance !

Don Elliott - 1958 TR3A
Don Elliott

Jean - When I removed the head for my TR3A, it was to have a shop put in new steel valve seat inserts for the exhaust valves because of "valve seat recession" after using the cast iron head for 43,000 miles from 1990 to 1997 with un-leaded gasoline. The un-leaded gas burns or "eats" a groove, recessed up into the cast iron head where the valve is supposed to seat. Also the valves get as sharp as a razor blade and I also changed all the valves and the valve guides too.

One of my concerns was that I had heard of some TR's where this had been done incorrectly and then a bit later, the inserts started getting loose. In some reports, when the insert fell all the way out from a lack of press fit interference on the diameters, the valves smashed against the insert which was no longer inserts, but circular collars which were now free to move all around between the valve going up and down and the head. This caused serious damage.

If your gap problem is only with the exhaust valves and you just had a shop put in new inserts (only for the exhaust valves) - then I think this might be the explanation.

Did you have this done while the head was in the shop ?

If so, I think the inserts are moving down a bit, leaving a larger and larger gap for the valve clearance. This would explain them getting noisy.

If you had this done, you have to pull off the head and take it back to be corrected or have a better machine shop put in new valve seats again. The shop that did mine here in Montreal explained all this to me. They supplied the seat inserts because they had the correct tools to machine the cast iron head to get the proper interference fit for their inserts.

They have been in the head of my TR3A for the last 27,000 miles and I never once had to re-gap the valve clearances. But I check then about evey 5000 miles to find out.

Don Elliott, 1958 TR3A

Don Elliott

Well Don,


Valve seats were only grinded as the machine shop guy said everything was acceptable. But I had valve guides replaced and unfortunately by 2 times exhaust valves stuck in guides soon after starting the engine. Finally TRF factory advise me that guides should be reamed. But I can not remember if if is one of the faulty valves-guides not retaining its gap. I removed engine head 3 times and I am bored of doing that, but the noise is quite annoying. What is embarassing is this kind of clatter reappearing after a valve adjustment.
Thanks, JGCatford
Jean G. Catford

Jean - So, it's not the inserts coming loose, because you don't have them. You'll have to have some put in, maybe in about 20,000 miles or less, because of "valve seat recession" where the cast iron gets eaten away by the "sans plomb".

If your guides were not reamed then I can only think that when the engine gets hot, the valve stems expand in diameter when hot (dilatation) and this makes the valves get stuck in the valve guides. If they can't go up and down, the noise will be there.

When a shop does valves and puts new guides in too, he should know that they need to be reamed. Before you put the springs back in, and after you put a bit of oil the valve stems, you shouhd be able to flick the valve up and down in the valve guide with just one finger.

Sounds to me you need to take it aff a 4th time.

Sorry

Don Elliott, 1958 TR3A
Don elliot

This thread was discussed between 16/01/2003 and 20/01/2003

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