[camino_man]

hey guys, got a 73 400 with a q-jet off a 77 olds thats been on it since ive had it, but dont know what cfm it is. im thinking of using a holley for awhile to see if it would make any difference over the q-jet. specs on my engine are 73 2 bolt main, flat top 4 valve reliefs, 882 heads pocket ported triple ange valve job decked, 9.5 : 1 compresion, comp 270h cam, .470 lift 224 duration, 1 5/8 full length headers, edelbrock performer intake, and the current q jet. i figure im makeing around 300 - 330hp. anyways what size carb should i use if i go to a double pumper?

[hause]

For That I Wood Choose A 750 If It Is Going To Be Used For Street Only But For Street/strip And Best Performance On Strip I Would Choose An 800 But If You Did That I Would Choose A Differnt Intake Like Rpm Or Something Equal To.

[firechicken383]

If its from a 77' olds, it may be a 800cfm. I got 2 800 Qjets, both off of 77 403 olds engines.

[badknuckles]

you shouldn't need anything bigger than a 650 dp that would be enough..it's not like your getting any added hp if you go with a 750 or 800cfm carb

[firechicken383]

you shouldn't need anything bigger than a 650 dp that would be enough..it's not like your getting any added hp if you go with a 750 or 800cfm carb

And I agree completely.

But keep in mind a 800cfm Qjet won't hurt you like a DP or something will due to it's "on-demand" design. Thats why GM can put a 750 Qjet on all kinds of engines, small small blocks to big blocks.

[Hippie]

You already have one of the best street carbs ever made, and it is at least a 750 possibly an 800. Just spend some time with it and get a copy of Doug Roe's book on Rochester carburetors. It takes a bit more patience and effort to tune than a Holley but it is also infinitely more tunable. It can be a real test of your patience and determination but once you get one dialed in the only thing better is EFI.

[stepside454]

I personally would consider keeping the Qjet....however, my second choice would be a 670 Holley for your application