The Stovebolt Site Forums The Shop Area Engine Shop Sudden, Severe Knocking

Dellman,

In the recent issue of Skinned Knuckles, I read an article on servicing the timing system. They gave the following simple test for the vacuum advance module on the distributor:

(from memory:)
Disconnect the vacuum line from the carburator at the distributor.

Manually rotate and hold the distributor in its usual direction so it's fully advanced (like it would be at full vacuum).

Hold your finger over the distributor vacuum port (on the advance module on the dizzy - not the vacuum line from the carb ;-)

Release the distributor body (while holding the finger over the port). The vacuum advance should hold the disributor in it's rotated (advanced) position. When you release your finger, it should only then rotate back to home position. If it rotates back immediately when you release the body, it indicates the diaphram in the advance module may be failed.

I thought this was an elegant, simple diagnostic test. Haven't tried it myself, yet, but hope it helps?!

-Michael