Engine Noise.

splatt · Oct 28, 2008

The bent push rods will be extremely noisy,is there any sign of the valves hitting any thing,ie piston.Check for loose valve guides as well,also head gasket leaking through middle,goodluck,let the spending begin&don`t tell mum.

Keith1069 · Oct 29, 2008

I may be wrong (often am) but the head clearance for the timing side inlet rod looks a little smaller than the drive side. Somewhere I remember reading that some heads needed relieving for the pushrods. I guess there will be clear evidence where it's been touching the head or barrel. I've overrevved my Combat to 7500 a few times over the years but never bent a pushrod yet. I'm sure Norbsa will sort it for you. Good luck.

Cookie · Oct 29, 2008

Arggh. I think I recall once putting in a hot cam that would have caused pushrod interference if I had not done a bit of grinding. Contact marks should be evident if that was the case.

tuono · Oct 30, 2008

Wear ear plugs, works a treat on mine and no it has never let me down in 27 years.

cash · Oct 30, 2008

Joe,
A bloody mess but not too expensive.

Did the noise start shortly after you set the valve clearances? Were any of the clearances large?

Cash

Cookie · Oct 30, 2008

Forgive my ignorance but it seems to me I read somewhere of valve train geometry problems with some Commandos.
I never realized how easy I had it working on the old Atlas and early Commandos.

jsouthard · Oct 30, 2008

Cash,

The noise was there before any adjustments to the tappets.

The only reason i got in there was to try to eliminate some of the clacking. It didn't change anything.

Norbsa has the head now. I should find out soon if the valves are ok. It looks like the head may have been put back together by the previous owner poorly (bent pushrods, bent gasket).

I'll keep ya updated!

Cookie · Oct 30, 2008

This is what I'd worry about. It is possible you have a cam with more than stock lift that causes interference with a stock gasket at high RPMS. I think I see intake push rod contact on the pix but it is hard to tell. It would also be possible to over rev the engine and cause the same problem.
The chances of somebody assembling it with rods that bent are quite poor.
It is also possible that a non stock gasket was used without enough clearance. It is easy to put them together looking nice and have them come apart looking bad.
I'd make sure I have good clearance on the reassembly.

norbsa48503 · Oct 31, 2008

By the markings on the tips of the valves the push rod geometry was way off. The bores were stock 850, 3.0385 through and through. but no sign of the hone marks of old though. Still have to pull the valves to check the guide wear. The tappet faces look like just normal wear good news all and all so far.

Cookie · Oct 31, 2008

What's your fix for that on the geometry? Different push rod length?

norbsa48503 · Oct 31, 2008

Maybe but Atlas Valve stems are on the list too.

Engine Noise.

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