Thermoquad vs Quadrajet

[Danny Ashley]

Jeff:
All Q-Jets were 750CFM (1.093 venturi) until 1971 when the 800's (1.218 venturi) were installed on Buicks. Pontiac got their's in 1973, Olds 1975, and Chevy also 1975. Not sure about Caddy's. The single booster were on Pontiacs in 1971. I have heard that they were on a few late 1970 and early 1972's. The 7041263 was used on low performance 400's and I think 455's. These carburetors venturi measures 1.093. I had one flowed and was told it flowed inbetween a 750 and a 800. The Pontiac community always refer to these as an 800. Is there an advantage to these over an 750? NHRA thinks so because they say they are only legal on the engines they came on. Danny

[Mark Yacavone]

It should be noted that most of the Chevy 350's and the 305's built after 75, didn't get the large primary (1.21 venturi) carbs . The SB 400's and the 454's did, though.

[Jim Wahl]

Danny,
Carter did make a Thermoquad they rated at 1000 cfm but it was an aftermarket replacement type carb. It was never an OEM deal. I think it was the Carter Competition Series 9000 and 9001 models. BTW none we ever flowed made anywhere near 1000 cfm. The 750 and 800 cfm ratings are much closer to being realistic but still over rated.
Jeff, I have never seen or heard of a "Red Bowl" Thermoquad. Sounds like an Urban Legend to me. The Motorhome Thermoquads were rated the same as the big block ones,(800cfm) they just had less smog crap involved. They were also available on certain big block Ford motors. Jim

[Neil Smedley]

I had a ` red bowl` 1000 cfm thermoquad years ago.....the only difference being the size of the primary boosters.......they took up a lot less area.......since most of the air enters the engine through the back barrels, I could not see an advantage

[Jim Wahl]

I have seen many of the bowls vary in color from black to dark brown. Remember these "plastic carburetors" bowls were made of a polyfiber-resin materiel that is rather fragile. The "red" could have been a different resin compound they were trying out, but again, I have done hundreds of Thermoquads for Stock and Super Stock applications and never seen one of the "red" bowls. Jim

[Run to Rund]

The 800 Qjet is easy to tell from the 750 once you have seen both. The outer ring (the primary venturi) is round in a 750, and larger with a protruding bump in it on the 800s. I've seen 800s on such unlikely stuff as a late 70s Olds 350. In that case, the linkage that opens the secondary throttle blades was restricted so they didn't open all the way.

[Jeff Lee]

The red bowl was marketed as a performance application. Mid-late '70's I think?

Wow...there's a Thermoquad.com site!
http://www.thermoquads.com/page203.html

CFM differences here:
http://promaxcarbs.bizland.com/thermoquad.htm