cocodrillo

After trying to set my timing up I’ve found that the vacuum advance on the Delco HEI isn’t working and it looks like the diaphragm is the problem. Is this part available separately? How can I find what model/part number this might be? Thanks.

HeadsU.P.

Where does the vacuum line go to, to receive manifold vacuum? (not ported)

Normally, I would say the canister is available at Summit, Jegs or even NAPA. But being a Mallory unit, it may not take the standard canister. IDK

Should be some code numbers on the inside of the dizzy, near the actuator arm.

If you have a vacuum hand pump tool, you can test the canister easy enough to make sure that is the culprit of your issues.

leadfoot4

Beyond that, the GM canisters had a code stamped into the bracket, which indicated the amount of timing advance that the canister provided. Different car/engine combinations had different canisters. However, since GM dropped vacuum advance controls over 30 years ago, finding a GM replacement part might be next to impossible, and that would be assuming that it would work with your aftermarket distributor. There are "field adjustable" advance units available, as mentioned, from the usual "speed parts outlets", as mentioned. However, before buying one, I would also "second the motion", about verifying that your current unit isn't working properly.

cocodrillo

Thanks guys, managed to find one on the shelf in the UK. I didn’t think it would be so easy.