Carb Question (not the Q-jet vs Holley debate)

[mr_clean]

I'm about to order my carb. I'm thinking of getting the Jet Stage 2 Q-jet.
Just wanted to know whether to order the 750 or 795 CFM version?

Engine is a freshly rebuilt 350

RV Cam
Flat top pistons
Vortec heads
Performer manifold
Exhaust will (most likely) be dual 2.5", Headers, and flowmasters...

Will 45 cfm's make a difference?

Also maybe someone can answer this for me...

Why do Q-Jets run so much bigger on cfm's for the same engine as Holleys?

 

[pauly383]

Ya probably don't need the bigger one , you will never see an rpm where ya can use it on trails or stoplight to stoplight . But you can run it if ya want to for bragging rights and it will run good even if you had less cubes .

They can run more cfm on a smaller motor with a Q-jet due to the smaller primaries , and the fact that the secondaries only flow as needed . And by having each GM divisions carbs in any particular year or era using the same basic casting , you just changed the tuning on each model . \

They changed a few times over the years , early divorced choke , hot stove choke , hot stove and bowl vent , electric choke and bowl vent , then CCC compu carbs . And BOP have a front inlet instead of Chevy's side inlet for fuel .

 

[mr_clean]

Thanks for the info Paul!!!

I've always wondered why stock 350's came with 750 - 795 cfm q-jets but if you throw a 750 Holley on there you'll choke it out if you ever get on it. Makes perfect sense.