Hi everyone, Thermoquads originally designed as a performance replacement for Quadrajet carburetors, So If I change my Quadrajet with a Thermoquad from 70`s 440 what will be advantage and disadvantages and besides fuel pipe from fuel pump to carburetor what else should be change?
Those mid 70s 850 TQs were quite lean for emissions. I would go up .003 to .005 on the primary jets and run .149 secondaries.
The 440 850TQs are cheap and you can get them to flow more (over 900) by removing the outer booster venturis and the choke. I got one to run within .05 of a 1000TQ so I sold the 1000 for 400 bucks years ago.
That would be the Competition Series aftermarket Thermoquads, not the ones off of the production line cars. Regarding the production line TQs, I don't think you'll gain much of anything over a well-tuned Quadrajet. Tommy
I like my Qjets but the TQ has many design upgrades over a Qjet such as dual bowls, cooler fuel, more air flow, better air valve design, replaceable secondary jets, adjustable primary rods. I've always run better with TQ vs my best QJet.
what I have for now is 6321 (1973 400 cubic inch engines High Performance, automatic, Federal application, 1 1/2 inch primary)
Here is a dyno test of a 800 cfm Qjet, Holley 950 Ultra HP, and a modified Thermoquad. The Tquad started out life as a 6322 850 cfm, the primary outer booster ring was removed as well as the primary bowl venturi bump, choke hardware removed, secondary throttle blades at 86 deg, sec air door at .780".
I dont have one but maybe can borrow one. Round 2 of testing is forthcoming if the crank grinder will get busy. I would suspect a Dom will give up a little on low end and have a stronger top end
Guess that will depend on the motor....that 950 didn't show any signs of being too big.......its odd even though we don't have the best heads onnthe market, buicks seem to love bigger carbs
Buick's like big carbs because of the restrictive heads, and large bore.. we have no airspeed problems that you can run into with other makes. JW
There is a lot to consider if your engine is not stock. There are 2 books available, or can send it to Ken Manley.
I rebuild and install that 6321 that I have just for simple test to know what is its reaction on 455 stage 1 and result was interesting. I spend time to tune it very as fine as I can. I guess I want to use it as test carburetor than go for competition series.
The one I bought. Printed in USA by HPBooks: https://www.amazon.com/Rebuild-Powe...s/dp/1557885559/ref=sr_1_1?crid=12RRBCFILA1NG The one I didn't buy. Printed in Communist China by SA Design: https://www.amazon.com/Rebuild-Modi...s/dp/1613250673/ref=sr_1_1?crid=2ECGHM1UKSBVT
