G12 1960 Noisy Tappets

[Biscuit]

Morning John, yes the c/case does have to be split to replace the cams/followers.

[Eric]

Noise is relative most AMC twins are noisy at the top end, but before rushing to split the crankcase and checking the cam followers etc check everything else you can on the top. The valve springs themselves make quite a lot of noise as the inner spring makes contact with the outer one. But the valve rocker can have a hollow worn where it makes contact with the valve stem, you can appear get the right gap with feelers but the working gap will be larger. You could also have wear in the rocker arm bushes or rocker spindles that will have a similar effect. I have heard that sometimes even the bushes in which the rocker spindles are located can become enlarged somehow and give false feeler readings. All of these things should be checked out before considering the cam followers, spindles and cams in the bottom of the engine. Have fun.

[RogerNorman]

I would endorse all that Eric has suggested but if the noise is more of a knock than just the normal rattle associated with the top end then the cams or their associated parts may well be the cause. For 15000 or so miles I have put up with a knock from my G9 that when it siezed a piston last year I decided to strip the engine right down having suspected a wearing big end. Nothing found. Rebuild and a run resulted in a quiet engine for 50 miles then even more noise. The engine is apart again now (glutton for punishment). It appears as if one of the camshaft bushes is worn and has been causing too much end float on the cams. So be warned - all may not be quite as you first suspect. Despite that, this time around new shells and main bearings were fitted. I couldn't face another strip down before going to France in June!