Carb CFM

[Dauntless]

Anybody know the carb's rated CFM for an early 80's Buick turbo?

TIA, Stan

 

[pat83t]

According to my carb book they are 800cfm.

 

[Dauntless]

Thanks!

 

[b4black]

Remember that the same basic Q-jet on a V6 was also used on a Big Block 455 V8. The V6 needs something like 390 CFM (IIRC). The spring loaded air valves control the overall CFM.

 

[fc227]

I think that the secondary is limited to open to 50°. Which limits the carb's CFM to around 560. If you go to big the car will buck & stumble.
Because this happen to me.
Even with the Holley on my car. I had to limit the secondary open because I was getting to much carb. & The Holley is a vacuum secondary carb.

 

[Scorp965]

Originally posted by b4black
Remember that the same basic Q-jet on a V6 was also used on a Big Block 455 V8. The V6 needs something like 390 CFM (IIRC). The spring loaded air valves control the overall CFM.

My 1980 3.8L turbo Buick V6 runs like crap and has a 795cfm carb on it, going off of what you are saying here on the thread this carb is entirely the wrong size for the motor? Or is this size correct for the turbo V6?

 

[b4black]

I've always run the stock Q-jet, so I don't know first hand. The turbo books I've read state that a turbo motor should have the same CFM carb as the NA motor. 795 is way to much for a 231 ci engine.

Fred (fc227) was running a non-ECM Turbo V6 motor like you have and he was limiting his carb.

There are car math calculators on the internet to help figure out the correct size.



You need a website with pictures of your car and motor.

 

[fc227]

About 570 CFM is all it will handle before it bucks and runs like Poop. (Turbo car, can answer about the NA engines)

Trust me on this one. I have been down that road.

Limit the secondary on the QJet so they only open 50° or maybe a little more.

See me right on the Gnttype page there is a picture of the screw I used to limit the secondary opening.

 

[fc227]

That should read "write up"

 

[BlaBlaBlaGuy]

u want to know why htey are 795 cfm carbs
well it all started in 71 before that they were all 750's

795 cuz more air less gas and carbs u can;t tune its a smog thing kinda kinda ahrd to explain

but u it started when they started making weaker motors in 1971
when gas prices shoot up