52' 300 timing / vacuum advance

Posted by ghoenshell On 2024/5/21 23:03:43

Its been a while since I last posted due to life getting in the way. I am getting back to working on my 52' 300 trying to get it ready to enjoy this summer.

It all started when I had issues with the accelerator pump in the carb not working and not allowing me to accelerate. So I ordered a rebuild kit from Max Merritt and rebuilt the carb. Got everything put back together and got the car fired up with using the base fuel screw settings of 2 turns out. It was idling higher than I would have liked, so using a dwell/ tach meter, I am able to watch the RPM and dwell with the car running. Currently the Dwell is set to 24 degrees which is within the spec of 21-30 degrees according to the service manuals. These measurements are taken with the Vac Adv disconnected at the carb and the carb plugged off. I cannot get the idle down to the factory spec of 450-500 rpm without the car dying. Currently its idling around 750-800 RPM with the Vac Adv connected, but has an audible miss at idle. It smooths out when given throttle.

I thought that the timing may be off since it won't idle at the correct RPM. After checking the timing with a timing light and Vac Adv disconnected. It is right on at 6 degrees BTDC which I believe to be within spec. When I check the timing with the Vac Adv connected, the timing jumps up to 16-17 degrees BTDC and continues to advance further when RPM's are increased. It has the Delco distributor if that matters.

My questions to the experts:
1. Is the timing supposed to be set to 6 degrees with the Vac Adv connected?
2. Is my advance of 16-17 degrees with the Vac Adv connected seem reasonable. Is this due to the RPM's being elevated above the normal spec of 450-500 RPM?
3. I assume if I can get the RPM to 450-500 then there shouldn't be any timing advancement from the Vac Adv? If its still advancing at 450-500 RPM is there any adjustment to the vacuum canister to reduce the advancement or does it need rebuilt?
4. Any other suggestions or areas to look at?

thank you for any insight or help you all can provide.