No start on rebuilt 360LA

jtn2655 said

Having worked all day, trying every suggested fix. It is still not working. Continuing to backfire through the carb. We have changed carbs, distributors, wiring, troubleshot the msd box, checked all 8 spark wires for spark, coil wire has spark, moved plug wire positions, rotated 180 then back 180 multiple times. Set initial timing, adjusted valves, you name it, we spent 8 hours doing it. Thanks for all your help fellas, but I am out of ideas.

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You are not helping yourself here by not being specific. Please DETAIL how EXACTLY you set up the timing. By the way have you CHECKED THE TIMING MARKS themselves for accuracy with a piston stop?

What I think I'd do at this point:

1....Use a piston stop to verify timing mark accuracy.
2....Look up cam specs, and figure some redneck way of monitoring valve lift, and by temporarily marking the balancer (masking tape, etc) estimate valve timing to see if it is correct
3....Carefully rotate the engine through an entire 4 stroke cycle of no1 cylinder. watch for compression with a gauge or your finger, watch for intake vacuum on down stroke, and watch the valves This will help confirm valve timing AND whether you somehow got a reverse ground cam

If all the above checks out, I'll say it again

JUST HOW exactly, step by step did/ are you setting timing?

WHAT have you done EXACTLY to determine that you do not have a valve(s) hung open that is allowing backfire?