250ci Exhaust Question

[jcwren]

So it's been a while, but today we finally got most of the carb issues and such straightened out on the '70 C10. Ended up putting a Holley 350 CFM Street Avenger on it, with a Transdapt 2bbl to 1bbl adapter, and a custom CNCed plate that holds the throttle return springs and throttle cable.

Fought a REALLY stupid battle with what sounded like a timing problem, and turned out to be that I had plugs 2 and 4 reversed. It actually idled really well, and at high RPM with no load, but as soon as it was under load, starting backfiring through the exhaust. Once I figured out that it was 153624 and not 153642, things got a lot better.

I've got a set of Hedman headers on it, and cylinders 1-2-3 go into one pipe, and 4-5-6 into the other. I'm getting what almost feels like 1/2 the flow out of the 4-5-6 pipe compared to the 1-2-3 pipe. We've reset the valves, and they seem to be correct. I have not yet re-run a compression test, which is my next step. We did one a while back and they were about a 5% spread from high to low.

I don't know what the effects of a slightly bent valve are, but I'm not smelling any excessive gas through the exhaust, and it doesn't seem to be blowing back through the carb.

Anyone have any advice and/or thoughts on this? I'd expect the exhaust flow to be fairly balanced between the two pipes, but I've sure been wrong before...