[SOLD] Bar Bet Winner!!

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whitepunkonnitro

whitepunkonnitro

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Ok, so nearly everybody knows that late 318 and 360 4bbl engines used Rochester Quadrajets from the factory, as the T-Quad was no longer in production. Alot of guys, like me for example have often used Quadrajets on our Mopars, just because they're so easy to work with and get parts for...but there's always that "thing" about using a Rochester...a GM carb on something born so superior to a mere GM transportation slug...it just ain't right.
BUT, DID YOU KNOW, that during the mid 70's CARTER was actually subcontracted to build Q-Jets for GM...and that these extremely rare carbs actually have the words "QUADRAJET BY CARTER" cast right into thier sides!
What I've got here...for a mere $100, plus the ride...is an actual CARTER QUADRAJET! It's in excellent condition, complete, clean and originally installed on a 75 Vette 350...but it's a CARTER!!...and that makes is spiritually ok to use on your MOPAR!. Pics to come, PM me if interested. Thanks FABO!
 
I believe New Process gear company was owned by Chrysler and GM at one time. Maybe they still are?

How many CFM does a GM Thermoquad flow? I knew they made them, but have no idea what they flow.I have a quadrajet on my 84 4x4 Dodge, and it is a factory piece.
 
whitepunkonnitro said:
The most common Q-jets flow right around 800 cfm.
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Sorry to burst your bubble but most Q-jets are actually around 725 cfm respectfully. There is a few models floating around that can produce around 775cfm. I only know this because when I was in school (UNOH) I did some flow tests on a few different Q-jets to prove other students wrong using a Superflow tester. needless to say they all started to dig out those Q-jets they tossed on the workbench to replace with a holley or edelbrock.
 
71Scamper said:
Sorry to burst your bubble but most Q-jets are actually around 725 cfm respectfully. There is a few models floating around that can produce around 775cfm. I only know this because when I was in school (UNOH) I did some flow tests on a few different Q-jets to prove other students wrong using a Superflow tester. needless to say they all started to dig out those Q-jets they tossed on the workbench to replace with a holley or edelbrock.
Click to expand...

You are correct that most only flowed 725. If I remember right there was 3 sizes of of Q-jets and the smaller one was only 650 cfm. The next one up was the 725 and a few rare ones used only on Pontiac RA or HO cars, Buick stage 1's, and Olds 442's were rated at 800 cfm. I never actually flowed them like you. Just what I gathered by reading a lot of info on them.
 
Good info. From what I understand, the smaller versions of these carbs had the same size throttle bore/blade, but the secondaries were restricted to only open a pre determined amount.
I myself have only used these carbs on engines where gas milage was the big factor. They always seem to get 2 or 3 more mpg's than T-Quads. Had one on a 318 headed 360 with an SP2P in a 74 Charger, and that car used to knock out better than 20 around town and very high 20's on the highway.
 
No, there were at least 2 different primary sizes and both had the same size secondaries. The base plate throttle blades may have been the same size (never measured them) but the primary venturi was necked down smaller in the smaller version. The secondaries don't open 100% on any of them, but close. Their designed that way because of the boosters. Same for TQ's. Their secondary throttle blades don't open 100% either.

I have only see the 650 and 725 versions so I'm not sure what was different on the 800's.

They are good carbs in spite of what some guys say. I ran a bunch of them on various GM's I had when I was a kid and had good luck with them. They have a small fuel bowl reserve and only 1 inlet so their limited on performance compared to a Holley but their still fine for most any street car under 500 hp and like you said they generally deliver good MPG
 
a properly tuned thermoquad will out perform a properly tuned q -jet in every way.
 
Lol whoops. Been a while since I read the article. I'll see if I can find it again and post a link

I remember it saying something only allowing 650, but as I said. I'll try to find the link
 
71Scamper said:
Sorry to burst your bubble but most Q-jets are actually around 725 cfm respectfully. There is a few models floating around that can produce around 775cfm. I only know this because when I was in school (UNOH) I did some flow tests on a few different Q-jets to prove other students wrong using a Superflow tester. needless to say they all started to dig out those Q-jets they tossed on the workbench to replace with a holley or edelbrock.
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little off topic but i am going to school at UNOH right now....


bump for the carb though
 
put one on my 340 in a ramcharger way to lean exaust manifolds were glowing red! it was my understanding a 4bbl was never offered on a 318 from the factory! just saying
 
moparman3406bbl said:
put one on my 340 in a ramcharger way to lean exaust manifolds were glowing red! it was my understanding a 4bbl was never offered on a 318 from the factory! just saying
Click to expand...

There were probably issues with the carb you were using if it was that lean. Even one jetted for a 305 Chevy should keep a stockish 340 happy.
As for 4bbl 318's..the original polyhead was offered with a 4 barrel until 62, and then the LA 318 got one in 85. The Q Jet was also the carb used on 360's from 85 up.
 
I wouldn't trust any flowbench to come up with an exact number. All I know is that I "estimate" the cfm at 700-725 for the small one and 750-770 fot the larger one, basically there are only 2 sizes unless you find the "holy grail" of Q-jets (1 year only Pontiac ). You can tweak them a bit to get a bit more cfm. Cliff Ruggles runs high 10's to low 11's (depending on the tune) in a Pontiac ventura with a real Pontiac motor (455 over). Just a great carb and you can find them for next to nothing. I have one on my 318, very adaptable! Mine is off a 85 dodge van w 360.
 
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