Dual point distributor ID question

mvh said

It's at a shop because my new HOA won't let me work on it in my driveway. They have been driving it w/o the vac advance, and they set the timing to stock (10ºB). But they just called to say when they did that, it made the idle slightly rougher, and they could hear the heat riser flapping, and now they're wondering if we both were mistaking that for pinging. So they are wiring it open as a test.

The motor is just far enough away from stock that's it's a little bit of a guessing game. Rebuilt years ago at .030 over, w/ TRW hypereutetic pistons, Crower hydraulic cam with a smidge more lift, plus a recent set of used heads with new valves and a mild port, 2-1/2" dual exhaust.

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That's too bad. You really don't know what you have for sure it seems. I would leave the initial around 10° to start. Some people continue to advance the initial until it kicks back against the starter and then retard it a couple degrees. No more than 32° or so at say 3000 rpm with the vacuum advanced disabled. Those original distributors don't have adjustable vacuum canisters unless you take the end apart and shim the spring. You can get into the advance mechanism's with lighter springs for quicker advance (which may have happened to yours) and the advance plates can be changed or the slots modified for more or less centrifugal advance. It's a science for sure and too much, too fast, or at the wrong time can cause detonation. A noisy heat riser is another thing. :BangHead: :BangHead: