Re: Ticking Sound at Idle on 120 Straight 8

Posted by Tim Cole On 2019/4/28 8:37:13

A piston noise should change when grounding a spark plug and snapping the throttle open. A piston pin should be a lower pitch and change somewhat when grounding the plug during deceleration after snapping the throttle open. A sticking valve should change after spraying Gummout down the carburetor. A broken valve spring will show up on a vacuum gauge. Tappet noise will occur when a valve stem is not exactly parallel to the tappet. It will change when putting heavy oil or a feeler gauge between the tappet and the valve stem. Loose valve guides will show up after putting thin oil down the carburetor. That is, the motor will run better. An exhaust manifold leak will change during acceleration and become less loud after warm up. It can be checked by putting small amounts of thin oil down the carburetor with the exhaust routed outside the garage, or by using soap and water when the motor is cold. An arcing coil will show up as misfiring during full throttle acceleration. A belt will go away when tension is changed. A fuel pump will remain fairly consistent and be felt through the pump body.

Hopefully you can make up a list now and work through the possibilities. Here in engineering I get to put everything in writing and when something goes wrong I take out the paperwork.