# Need a new carb, need sugestions



## SmokeyBrisket (Jun 26, 2017)

70' with the 6.6 400. I need to replace the carb. Currently running a quadrajet. Would like to run a Holley. How much cfm should we run? Thanks for help fellas.


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## bigD (Jul 21, 2016)

A properly rebuilt, functioning, & tuned Q-jet is real hard to beat, for a street driven Pontiac. 

Obviously yours is not functioning properly, or you would not be wanting to change it. 

SMI can build a good one for you. 

SMI Carburetor Street Performance Rochester Quadrajet 800CFM Buick, Oldsmobile and Pontiac Quadrajet 4BBL SMI- Sean Murphy Induction

But, if you insist on going with a square bore Holley type carb, a member here did some testing and found that a Quick Fuel SS-680-VS was the best carb for his street 400.

http://www.gtoforum.com/f178/opinion-carberater-400-motor-86857/index2.html#post624025

http://www.gtoforum.com/f178/opinion-carberater-400-motor-86857/index3.html#post624121

https://www.amazon.com/Quick-Fuel-Technology-SS-680-VS-Carburetor/dp/B003M8YV4I

If you think you need more cfm, these carbs come in 735 & 780 cfm models. Looks like Holley bought out Quick Fuel, a few years back. They are now listed on the Holley site.

https://www.holley.com/products/fuel_systems/carburetors/quick_fuel/street/ss-series/parts/SS-735-VS

https://www.amazon.com/gp/offer-listing/B003M96AWI/ref=dp_olp_all_mbc?ie=UTF8&condition=all

https://www.amazon.com/Quick-Fuel-T...coding=UTF8&psc=1&refRID=9ABVTWQ62P5PHZ2WXVZM

I assume you already have an intake that will accept a square bore carb ? If not, you'll need to buy one or use a spread bore carb. Most do not recommend using a square bore carb with adapter, on a spread bore intake.

Many good Pontiac engine builders say that an iron intake with a good Q-jet are good up to around 500hp, if you have enuff motor to make that much power. And, there are enuff 10 sec Stock class Pontiacs and dyno tests to prove that is correct.


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## Pinion head (Jan 3, 2015)

SmokeyBrisket, what part number Quadrajet is on your '70 GTO's engine? 
The engine has its stock 1970 cast iron intake?
How high would you rate decent mileage along with outstanding throttle response?


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## SmokeyBrisket (Jun 26, 2017)

Pinion head said:


> SmokeyBrisket, what part number Quadrajet is on your '70 GTO's engine?
> The engine has its stock 1970 cast iron intake?
> How high would you rate decent mileage along with outstanding throttle response?


. Not as worried about mileage. Car will stay local. I'll post carb pic below


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## SmokeyBrisket (Jun 26, 2017)

Current quadrajet. Lemme check on intake. Should be original


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## PontiacJim (Dec 29, 2012)

SmokeyBrisket said:


> Current quadrajet. Lemme check on intake. Should be original


Appears to be a 1970 455CI carb off a full size car. Made on the 268th day of 1969. The engine is listed as the 360HP, automatic, block code YH, 10-to-1 compression. *7040262* should be the complete number, but cannot see it all in your picture.


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## Pinion head (Jan 3, 2015)

the " 262" 455 carb can be recalibrated to run extremely well, or you can go down the swapping out intakes & spending several hundred on an entry level to moderate expense Holley square bore carb & get less throttle response & worse mileage. Experienced it too many times.. Until ones Qjet equipped heavily modified Pontiac has put itself in a position where it's running out of fuel in the bowl, it makes no sense to go to a center hung fuel bowl Holley.


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## BearGFR (Aug 25, 2008)

Most of the problems with a QJet will have been caused by the last person who worked on it and had a lifetime membership to the "secret trick of the month club", and thought they knew what they were doing.

They are very good carburetors when set up correctly. I'm running one on my '69 GTO and it's an honest 11-second real street car.

Cliff Ruggles is a well known expert on them, and has had a good book out on them for a long time.
https://www.amazon.com/Rebuild-Modi...&qid=1505659217&sr=8-1&keywords=cliff+ruggles

He rebuilds them (but there can be a significant wait involved as he tends to stay very busy), or if you're reasonably handy you can do it yourself with the information in his book.

There are others out there also but Cliff is the only one I've dealt with personally. I built my own using his book, and some advice from him.

Bear


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