[Formulafr]

i really thinking about changing my carb to a new one. what is the best way for my 350?
i'm looking for a Holley 650 spread bore vaccum (80555c). does other than Holley make this kind of carburetor?


i know the formule CIDxRPM/3456=Cfm needed, and that's why i don't want a bigger a carb (thinking about mileage too).i prefer a small but at 100% use than a big at 80%. do you think it would be better with a 600 or less? is there a mileage difference beetwen 600 square bore and 650 spread bore?

[Formulafr]

i really thinking about changing my carb to a new one. what is the best way for my 350?
i'm looking for a Holley 650 spread bore vaccum (80555c). does other than Holley make this kind of carburetor?


i know the formule CIDxRPM/3456=Cfm needed, and that's why i don't want a bigger a carb (thinking about mileage too).i prefer a small but at 100% use than a big at 80%. do you think it would be better with a 600 or less? is there a mileage difference beetwen 600 square bore and 650 spread bore?

[KS circutguy]

Why not get a Qjet?
Have Cliff build you one for your application. Much less trouble than a holley, better all around performance too.

[David Jones]

I'd go with a Qjet. They came on all size engines. Contact Cliff Ruggles and tell him what you have. He can supply the correct carb. Does he ship international? Good question. I've got a 650cfm Holley spreadbore, sitting in a box in storage, that did fine on my 400. Cliff's 800cfm Qjet works better.

[Formulafr]

when you say Q-jet work better, what do you mean by that? better filling? more mileage? can you explain why please

[Mr. P-Body]

A "spread bore" has tiny primaries and large secondaries. What "works" better, is that mixture velocity is quite high through the primary. The result is "better" cylinder packing at low engine speed. The secondary doesn't rely on velocity nearly as much as the primary, and the large bores provide the volume needed to allow the engine to rev to a "performance" RPM range. For a street-driven engine, it is usually prefered to go with the Q-Jet.

[Formulafr]

i know the problem of velocity and that's why i would choose a spread bore instead of a square bore.

as every body say "go with Q-jet", i have a question ; what do you think about remanufactured SUMMIT Q-jet? i was looking a new holley because of the price but i know remanufactured carb are cheaper.

[68lemans462]

qjet...

[Kenth]

After reading this you´ll get the ide´a:

http://www.442.com/oldsfaq/ofcrb.htm#Carbs

[TransAm525]

I too vote for a Quadrajet. When properly setup, they will out-perform nearly all aftermarket carburetors. By using a Q-jet, you will see higher fuel mileage, better performance, and have much more tune-ability than any other carburetor available.

[carbking]

Kenth - whew! That is a looonnnngggg article.

Jon.

[LeighP]

I tried a 650 spreadbore vac secondary Holley on my 400. Got the same fuel economy, but when I finally found someone who could rebuild and tune a Q-jet properly, the Q-jet blew the Holley away for part throttle response and driveability etc.
The Holley is far simpler to tune and play with (for me anyway...lol), but I'm a confirmed believer that Q-jets are good gear!

[sixt8bird]

I installed a Holley speadbore DP on my old 350 Pontiac and it kicked ass. I had to up the primary jets about 4 steps and like I said it did real good. at 200,000 miles it pulled an 8.7sec 1/8 mile It sucked in the 1/4" 14.90 but with 308 gears, I guess thats pretty darned good for a 350. Any carb " equal in CFM", if set up right for your car will run good.

[Formulafr]

i have a friend who has a Q-jet from a 76 camaro. if i buy it, i just have to rebuild it (few years out of the car, but stored in a bag with WD40) with some new gaskets.

[jamesgennock]

Quadrajet!