Thumpr cam crap

65Val said
OK...just to add more grist for the mill...do you have access to a Holley carb, say, a 600 or the proverbial 3310 750? (Now all you guys just hang on to the "But you're a Carter guy" comments for a sec...) He's changed everything except the carb and the cam. Holley's out-of-the-box seem to tolerate big cams better than Carter/Edelbrock's, so my thoughts would be to try a different brand carb and see what shakes out. Could be that 1406 just doesn't like Thumper cams.....

Just my $0.02

That's because metering rod carburetors don't like it when they have low vacuum. They cannot decide where the metering rods need to be so they bounce them around due to low vacuum. Metering rod carburetors are very difficult to get right with larger camshafts.

I think changing the camshaft here is a mistake in trying to solve this problem. While the camshaft timing could be an issue, the camshaft itself is not.