I started the 454 70 chevelle yesterday and took it out for a spin since it was a really nice day here. Started with little or no trouble. Warmed it up with the usual driveabilty issues. After it warmed up I started noticing a miss on light acceleration. Yet under full acceleration it pulls fine with out a miss. Carb is still wired to only open up with the 2-barrel operation until I get a few more miles on the new engine. So performance isn't stellar. After diagnosing it I found the vacuum advance would not hold a vacuum on the diaphragm. So I need a new one of those. Yet I doubt it would cause a miss on light acceleration. I plugged the vacuum line going to the vacuum advance to see if it would change. No change noticed.

Spec's are as follows:

468 cu in .060 over 454
Roller cam .512" lift 230 duration.
Quadra jet carb professionally redone by a Quadrajet specialist (who I believe knows what he is doing).
Stock distributor with a pertronix Hal effect/new pertronix coil.
New wires
New AC delco plugs
New Dist cap
10:1 with dome pistons, running premium fuel.
Heavily reworked 781 heads, ported and polished, bowl blended.
4 spd Muncie 3.08 gears


Any ideas what could be causing my light acceleration miss?

I recently built a 468 also and it had a quadrajet but on a edelbrock intake and i had the same problem. the carb was supposed to be redone and jetted out to a 850 and all that jive. i had a light miss on acceleration also. the quadrajet was sucking air from the base of the carb. and no matter what i did it was always lean it would run good with my foot on the floor. so i put a 750 dblpmper holley and it runs extremely better. i dont know what intake you are running. but thats my story and how i fixed it.

Thanks I will check it out. I am running a true LS5 cast iron (yea I know too heavy) intake manifold.