sbc 350 stumbles?

You said 600 holley.

Vacuum secondary?

If it has ever backfired through the carb, replace the power valve.

....and categorically stating it ISN'T the carb, almost guarantees its the carb

 

but wouldnt it be sputtering at idle when i rev it up?

 

I'm having the same issue, I called a buddy, he said its just a little out of time, check that it might do it some good.

 

vac secdeory coming in to soon, try a harder spring in vacam port

 

well was driving earlier and car would cutout and die.would wait a little then would fire right up.and then stumble and die think its the carb.

 

just replaced the rotor was looking at it and the metal contac was broken off.havent drove it yet but will report back tomarow and see how it drives

 

ok put a carter avs from a 440 chrysler doesnt stumble anymore or break up drives real smooth..thanks everyone

 

check the powervalve on that old holley, I had one that was too rich for my enigine due to the low vacuum readings because of my cam, so a 6.5 pv was flooding it, a 4.5 is just right for me and "under load" your vacuum decreases in gear...

 

Initial timing on any engine depends on many factors. Initial timing can be somewhat retarded, to over 20 degrees, depending on how the engine is put together. My mild sbc in my daily has 12 degrees. The more modified sbc in my other car has 18 degrees initial.