I have a 7.4L 300HP carbed motor. I'm changing the carb out, what size holley 4150 should I use and what size jets? Also changing to a air gap intake on recommendation from OSO. Thanks in advance!

750cfm

look into barry grant sea demons, had very mixed results with holley marine carbs.

In fact I would recomend calling their tech line for a size recomendation.

http://www.barrygrant.com/demon/default.aspx?page=21

I agree with Griff. Anything more than a 750 will be too much for that motor.

The reason i suggest calling tech is that Demon carbs are wet flow rated and therefore do not directly compare to holley numbers.

thats like there fuel pumps are like 15 volts

The holley 4779 would be a good one,or the new version of it, or the BG speed demon,just order the j tubes or order them from Gary Williams carburetors,mississippi,he also sell carbs.
The BG seems cheaper than the Holleys,last time i shoped them.

A 4 corner idle will be better

http://www.barrygrant.com/demon/default.aspx?page=5


http://www.jegs.com/i/Barry+Grant/13...010VE/10002/-1



http://www.summitracing.com/parts/HLY-0-4779C

droplegs, hp version
http://www.summitracing.com/parts/HL...1/?image=large


if your planing on moving up in power in the future, step up to 850+