I recently installed a comp cam 280h in my 305 and I have a Holley 4160 600 cfm carb with the stock power valve,which is a 65. At idle in park I have 11 inches vacuum, and in gear I have 7-8 inches. I notice when I quickly step on the gas it hesitates for a moment but then it starts to boogie. From reading around the threads it seems that i may need a different PV size, just wondering if anyone had any ideas?
Thanks,
Kronos

 

you should have more vacuum at idle than that with that cam, did you adjust your idle mixture screws for maximum vacuum while idling hot in gear? Are you trying to floor it from a stop? if so then i'd say you need to adjust your secondary spring tension with a stiffer secondary spring, it might be opening too soon causing the bog you describe.

 

I actually have yet to adjust the idle mixture screws, and the hesitation happens anytime when I floor it. The secondary spring that is in there is what came with the carb and it takes a while for it to open, so it's kinda tight. Even when I'm cruising I get little bumps in the idle, almost sounds like a miss. When I go to WOT there is the little hesitation, and then it smooths out while on the throttle.

 

recurve the distributor to allow more timing at idle. 20-24deg
A 4.5" power valve is best