Originally Posted by cobalt327
So it idles w/60 degrees BTDC and then the mechanical advance adds to that? Yikes!!
As long as you've confirmed TDC, firing order, etc. like you have, unless the carb is way out of tune/faulty/"modified", there's no way it should need anywhere near that kind of timing. So I'd start w/the carb:
As long as the carb is working right and not too far from factory specs, I'd start by baselining the transfer slots of whatever carb you're using. Then use initial advance and idle bypass air to get it to idle w/o the primary throttle blades being open too far. This can be done in several ways depending on the carb; a Holley can use the secondary throttle shaft adjustment screw to tip them open a little. If bad enough (although this is rare) holes can be drilled in the primary blades, but that's only as a last resort.
I've used 2 carbs. The one i'm using now is a 750 holley vacuum secondary. I closed the secondary throttle blades and cracked them 1/4 turn so they don't stick. I have the idle set at 750 with the primary blades. I never did see how the primary throttle blades look on the transition slots but I don't see how that would cause my timing problem. The carb is exactly how it came out of the box except idle mixture screws, float level, and i did lighten the secondary spring.
Could the spark plug really be firing when the crank is 60 degrees btdc at idle? I wouldn't think it could run let alone start. I'm just wondering if it's actually firing at 12 or 14 and somehow i'm coming up with 60.