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MG MGB Technical - Rocker covers and valve noise

Alloy rocker covers are supposed to "muffle valve gear noise" according to the catalogues. My experience is the exact opposite.

After I replaced the far too noisy exhaust system on my ´63 MGB last year, valve gear noise suddenly became very noticeable. I know everything is in good condition, and clearances are spot on. Yesterday I replaced the alloy cover I have used for the last three or four years with the original steel cover, and the engine is now much quieter.

This should perhaps not come as a surprise, because if you hit the alloy cover lightly with a screwdriver it rings like a bell, and if you do the same thing with the steel cover you only get a soft "thump".

Anyone else with the same experience?

Tore

Tore

I've had alloy rocker covers on my last three MGBs, but this one I bought last year I've kept with the standard steel cover. I've not noticed to be any noisier, if fact it's probably quieter, although that maybe down to the fact this is a low mileage, healthy engine. I haven't even bothered fitting the sound deadening pads I bought for the bonnet.

I'll be interesting to see what the general consensus is on this.

~Mike
Mike

Another advantage with the original steel cover that I had almost forgotten is of course that it locates the cork gasket much better.

Tore
Tore

Tore I would have to agree that the alloy cover is a bit noisier than the OE but you will find the best way to keep the noise as least you can is to have a good thick rocker gasket and good rubber grommets on the top and only tighten enough to avoid leaks. This insulates the cover to a great extent. People tighten the rocker cover as if it holds the head on and its not necessary and transmits a lot of extra noise.
Denis
Denis4

A few years back I got an alloy rocker cover from Moss, Fitted it about two years later. Terrible racket, rockers were striking on thick spots. Had to superglue two gaskets together to get enough clearance.
c cummins

Tore, just have a look on the inside, and see if there has been any contact with springs or rockers. Some of the castings are not very accurate, and also quite thick, so you can grind away until you have good clearance.

CP
Colin Parkinson

I've had mine for years and it is just as noisy as the original. The gasket problem is not the alloy cover's fault. Most of the rocker cover gaskets, in production today, are not as thick as the factory gaskets and cause the hold down nuts to bottom out way too early. RAY
rjm RAY

We find the ally covers tend to be 'louder', we fit ally covers on all our engines as they are very smart and it is almost impossible to find a dent free, beautiful steel cover.

Peter
P Burgess

Dear oh dear. Aren't alloy covers supposed to *reduce* tappet noise? I know I'm a dinosaur but given the apparent opposite effect plus the other problems mentioned this, as in many other cases, is surely a classic example that sticking with what Abingdon decided is best. Smart maybe, but crap!
Paul Hunt 2010

I wonder how someone, sometime got the idea that alloy covers reduce valve gear noise?

Tore
Tore

I Haven't a clue why people think the noise will be reduced Tore. Mind you, once tappets are set and the noise is as low as it can be, the level of B series tappet chuckle isn't too bad IMO.

Most steel covers have been overtightened to stop leaks over many years so it is difficult to get a good'un.

Peter
P Burgess

I LIKE the tappet noise!

Simon Jansen

I fitted an alloy rocker cover to the GT this morning.

I’m very impressed with the way it has brightened up the engine room. The bonus was when I took it for it’s obligatory daily run – it really has quietened down the valve train noise. No, it’s not placebo effect because I can now hear that lovely exhaust burble instead of the clattering rockers. Yes, the rockers are properly adjusted and no, I didn’t re-adjust them prior to fitting the cover.

Love it!



J Tait

I think the noise factor is more down to the noise damping effect of the fittings. Any cover fitted with a decent cork gasket and the correct rubber donuts for the bolts is going to be quieter. IMHO it's worthwhile replacing the donuts annually. I've seen alloy covers that have no rubber donuts but simply use washers for a seal, these will cause greater resonance through the cover.
Mike

Hi Mike

I reckon the replacement seals available aren't as oil proof as they originally were so you are right to replace the seals fairly frequently.

The A series 1275 engine is quieter than the B and the A series 1000 is quieter than the 1275. Seems to be an accoustical problem with the block design.

Peter
P Burgess

Fitted one of the Ali. covers a couple of years ago. Did not notice if the engine noise sounded any louder afterwards as it rattled a lot before fitting.
I have recently overhauled the engine, including sorting out the rockers and shaft. The engine is much quieter now. problem is I can now hear the alternator is clattering and it was only replaced a couple of years ago. Another case of rubbish replacement parts.
Trev
Trevor Harvey

This thread was discussed between 07/06/2010 and 10/06/2010

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