Half speed top end loud tap

I have a Mk 2 3.4 that has a loud tap from the region of the head at half engine speed all tappet gaps are o.k. and the tappet guide don’t seem to have moved, When cold engine makes no noise, as it gets hotter the noise increases to a loud tap. Any ideas please

If indeed the tappets are not suspect, could be a gudgeon pin, and/or a collapsed piston.

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try a vacuum gauge, compression test, leakdown…if something is not right internally, it may give an indication

I thought you guys called them “wrist pins” and we and the Brits and the Kiwis called them gudgeon pins? Paul.

Either works…:wink:

An easy way to check wrist (gudgeon) pins is to warm the engine till you hear the noise at idle, then with a WELL insulated puller, pull one spark plug cap off one plug and listen for a difference in the tap. If the tap still there, replace the cap and do the same on the next plug. If you find one where the tap goes away, you found the problem. That way I found an engine re-builder installed a rod and piston 180 degrees around and the engine didn’t like that after a few thousand miles.