The great CFM debate

[77cruiser]

What year did GM go to all 800 CFM Qjets? What year did they start using 800's on Chevys?

[omaha]

I always thought that they made the smaller version all the way up through the late 70's. '78 or 79 but mostly on chevy trucks. dont know exactly for sure. good question

[77cruiser]

I was thinking 78 or 79 they made the switch to 800's. I not 100% though.

[Cliff Ruggles]

Marine q-jets were 750cfm, and they will be the early style float/fulcrum arrangment, although they did make them in both divorced and electric choke models.

Chevy divorced choke carburetors were 750cfm, all years, all models.

Front inlet carburetors, hot air or electric choke were 800cfm castings 1975 and later.

The only divorced choke 800cfm castings were the Buick 455 carburetors, from 1971-1974.

The 1973 and 1974 Pontiac Super Duty carburetors were the larger castings, and had hot air chokes.

Side inlet carburetors, hot air and electric were made in both 750 and 800 cfm castings.

 All of the single main airbleed models (except late 70's divorced choke Chevy truck carbs), which started showing up in 1979, will be the larger castings.

There were no large cfm castings made prior to 1971, that I am aware of......Cliff

[4speed]

I'm a Pontiac guy. and look for a 800 cfm q-jet is tuff.  I think 73-4 HO and SD motors and 77-79 W72 400 motors.  Cliff did all years use them or just on special year motors.