Just put a very nice and clean 30,000 mile 250 in my '63 Biscayne. Put all new gasket set in it and it's running rough, probably a carb issue. But what should the initial timing be? It has HEI ignition with vacuum advance. Does it need to be set with the vacuum disconnected?
Thanks

I just read in my repair manual that the base timing for the 250 should be 6 degrees BTDC. The book covers from '62-'68, but I can't see it being any different for a '74.

Yes, the vacuum advance must be disconnected to set the timing.

Thanks! That's what we figured, just wanted to make sure before replacing carbs.