Carb Malfunction??? Help

[RocketChevy56]

I finished my new 355 and got her running about 4 weeks ago. I used the same carb as my last engine (650cfm street demon) I took special care in storing it in a carb box and put it up and away from anything that may harm it. After the first 50 miles or so of running it on the new engine, I've lost the ability to cruise above around 55mph. If I do, it bogs down and cuts out. Sometimes I can cruise just fine at 65+ and then out of nowhere it just give up. If I shift into neutral it acts normal and smoothes out. so it happens under load only. Could my floats be sticking? Perhaps a blown power valve diaphram? Might should have stuck with my reliable Holley.......

[MT71c-10]

Fuel pump? I've had them do this to me, at lower speeds. Or fuel filter?

[RocketChevy56]

I forgot to mention that I originally thought the fuel filter too. That was the first thing I changed. I put a clear one only to see what was in there. The pump is a Mechanical High Output Carter. I wouldn't think its going out, but I won't rule it out just yet. Wouldn't the pump act funny whether it had a load on it or not if it was going out?

[dwcsr]

I had a similar issue and it turned out to be I needed a phenolic spacer between the manifold and carb. After it warmed up and ran for about 20 minutes it would do the same as you describe. The bowls would boil the gas up the tubes. The spacer took care of that.

[RocketChevy56]

very interesting. I've noticed my bowls level never seems to be right when its warm, no matter how I adjust them. that might be worth trying if I find one cheap...just to see. thanks for the input keep em comin!!!