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Discussion Starter #1
how many CFM would the Quadrajet on a 78 350 have flowed? As well as on the 455 buick, pontiac and olds motors?
There are scads of them in the wreckers here and I was thinking of saving a few dollars on my carb purchase and work with the jetting etc.
The engine will be a semi mild 350 with the usual port matching, cam and headers
Thanks
 

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There are two sizes of the Quadra-Jet available, one has 1-3/32" primary bores and the other has 1-7/32" primary bores. The secondary bores are 2-1/4" on both carbs. The smaller one flows 750 cfm and the bigger flows 800 cfm. The smaller Quadra-Jet was put in to production in 1965 and the one with the bigger bores was introduced in 1971. The 78 350 would most likely have been the 750 cfm one and the big blocks could have had the bigger 800 cfm one. However, my '66 396 came with the smaller one originally so the little one is very capable of dealing with large engines.
Quadra-Jet carbs are very combination specific and sensitive, they were matched to each engine and vehicle by a computer at the factory when the vehicle was manufactured. They are by no means easy to work on, aftermarket parts are few and far between. I have three of these smaller ones and I don't want to mess too much with them, if a rebuild does not fix 'em, they go into the scrap pile. There are numbers on the main body of the carbs that tell what year and vehicle they came from. If you can, find a carb that comes closest to what you already have, rebuild it and see if it works, rebuild kits don't cost that much and if it doesn't work, find another. Try this book: Rochester carburetors by Doug Roe , from HPBooks. I got mine from my local Barnes and Noble.
 

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Discussion Starter #3
Thanks!, thats exactly what I was looking for. My carb id shows it as a 78 350 q-jet. I'll try a rebuild kit out on it
 

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One of the best things I have done for my elky was get a Edelbrock carb for it. I got the 1406. It made a big difference in the driveablity.
 
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