Big Block, HEI, Holley 750. 36 degrees at 3000 RPM. Mixture screws adjusted pulling 17 in of vacuum. No vacuum leaks that ai can find after spraying carb cleaner everywhere. put on a spare 650 Holley that was known to work and nothing. Floats adjusted property. Fuel pump replaced. Filter replaced. HEI swapped out for a different known working HEI. Replaced PCF valve and breather. It's a new build.
Does it rev cleanly without load? Does vacuum remain steady under light acceleration, say 5-10"? By steady I mean not fluttering,
It does rev cleanly without load. I would have to run a vacuum line into the car to check it under acceleration
I'd check vac, possibly it has a exhaust cam lobe going flat, valve hanging etc. If vac flutters & swings toward pressure, cylinder isn't being evacuated on exhaust stroke. In that condition idle/no load is generally OK, but under power spits back into intake.
Ok, that is worth checking. I just was fooling around with it at lunch and it actually starts popping a above 3000 rpm when I rev it in neutral. Didn't notice it when I was setting timing because I only revved to 3000 RPM.
You nailed it. Vac was fluttering. Our a dial gauge on the lifters and found 2 wiped out exhaust cam lobes. Thanks for the insight. Looks like it is time to pull the engine and see how much damage I did.
I ended up going MUCH richer, and it pretty much stopped sputtering. That said, I ended up going with a much larger carb. Sorry for the late response, I don't get on this site as much as I used to.
