1972 C10 Idle speed

[brown7373]

I continue to find it impossible to set my idle speed. This is a 4 month old crate 350/290 engine. I an running a non HEI distributor with Pertronix 1 in it, with timing set to 12 degree BTDC and HEAVY advance springs installed. I am using the original Q-jet that is rebuilt and vacuum advance to the distributor is disconnected and plugged. When I set the idle to 650 in gear, all seems fine. When I drive it, or take it out of gear, the engine speed goes over 2000. Timing advances 13 degrees (on my dial back timing light ). The carb linkage still rests on the idle stop, so it isn't a case of the carb opening. I used the same distributor on the old engine and it functioned fine.

If I reduce the idle from where it is racing, it will continue to drop and eventually stall. I can find no vacuum leaks and my booster holds vacuum. I suspect the distributor advances and that is causing the engine speed to increase. If that is what is happening, why would it do that with vacuum advance disconnected and very heavy springs installed on the weights?