I have a 482 bbc mild drag race engine with .714 lift cam and it stumbles 95% of the time off of idleWhen Im drag racing I leave the line a 3000rpm and it doesnt hesitate thenI called Crane cam and the tech told me its because of that big cam and im not creating enough cylinder pressure off of idle.I cant really flash it up to get my stall converter's flash stall because it hesitatesIf dont hesitate at all during idle it only does it when in gearIt doesnt hesitate if I hesitate if I bring the rpm up to 2000rpm and nail it eitherI have a 1050 Holley dominator and my cam works from 4400 rpm to 7800rpmIm just trying to get a second oppinionthanx
A stumble off idle is norm due to 1 of two thingsNot enough fuel or too much fuel Start with making sure floats are adjusted right(remove sight plug, crank engine, adjust so fuel just is at bottom of sight plug hole) Set idle mixture screws (all 4 of them) to get the highest vac reading on a test vac gauge) Now you get to the pump cam and pump shooter tuning (this is what I think your stumble may be coming from) It's a test it and see type thingKeep changing pump shootersYour looking for the smallest sized one that will still give you good clean throttle responce Now change out the pump cams to help clean up the responce even more Also check your fuel pressure7.5 psi is the most pressure you want Also ign timing can play a role in the stumbleWhats your timing curve? With that engine and cam, I'm guessing your not running a vac advanceIf you can, I would give vac advance a tryUse an adjustable vac can, set it up to give you just enough extra timing to help part throttle but not cause detonation8-12 is normHook it to a full intake vac Howes the mechadvance rate on your dist.? OH BTW what compression ratio are you running? Better yet would be a cyl psi (cranking compression) test to get the real cyl pressure 's And what duration is your cam and what LSA? Going from the .714 lift I'm guessing roller cam around 310 advduration and 276 or so .050
