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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.
…….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.
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.
Help please-HEI distributor diaphragm
