Alternative to Using a ThermoQuad
#2659476
05/26/19 09:52 PM
05/26/19 09:52 PM
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Joined: Aug 2003
Posts: 2,576 Fargo ND
moparphilll
OP
master
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OP
master
Joined: Aug 2003
Posts: 2,576
Fargo ND
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The Question: What are the options OTHER THAN using a ThermoQuad Carb on my 340 to get the SAME height so my Shaker Bubble does not rub on Hood. I used a Base plate under a ederbrock performer carb and it raised the bubble to high. Do the make a replacement carb for the 71 thermoquad?
Last edited by moparphilll; 05/26/19 10:05 PM.
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Re: Alternative to Using a ThermoQuad
[Re: moparphilll]
#2659498
05/26/19 11:00 PM
05/26/19 11:00 PM
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Joined: Dec 2007
Posts: 18,153 Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,153
Mass
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The Question: Do the make a replacement carb for the 71 thermoquad? Personally I'd make the TQ "work"...but if your seeking a "newer" alternative, there's the Demon
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Re: Alternative to Using a ThermoQuad
[Re: DAYCLONA]
#2659541
05/27/19 08:14 AM
05/27/19 08:14 AM
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Joined: Jul 2003
Posts: 4,741 Holland MI Ottawa
2boltmain
master
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master
Joined: Jul 2003
Posts: 4,741
Holland MI Ottawa
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The Question: Do the make a replacement carb for the 71 thermoquad? Personally I'd make the TQ "work"...but if your seeking a "newer" alternative, there's the Demon Yes this. If the Demon here will work your not only getting a brand new carb but an improved version of the Thermoquad. The Demon incorporates the best attributes of the Thermoquad the Quadrajet and the AFB with some additional improvements. Gentleman who designed it worked for Carter back in the 60s and 70s.
Keep old mopars alive.
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Re: Alternative to Using a ThermoQuad
[Re: 2boltmain]
#2659544
05/27/19 08:22 AM
05/27/19 08:22 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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^^^ sounds like a good plan assuming the "height" ain't a problem.
live every 24 hour block of time like it's your last day on earth
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Re: Alternative to Using a ThermoQuad
[Re: moparphilll]
#2659882
05/28/19 09:14 AM
05/28/19 09:14 AM
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Joined: Jan 2003
Posts: 11,892 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 11,892
Benton, IL.
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The Thermoquad was a pretty good carb in it's day, but they were not without their problems. And as with any 50 year old carb, they were designed to run on a very different fuel than they would see today. So, any Thermoquad would need a bit of work.
The Street Demon was designed by an former Carter engineer, which is why it is similar to the Thermoquad. But it has a number of design features that set it apart from any other mild street oriented carb out there including the Thermoquad.
Go with the Street Demon. As mentioned, the only issue that might be encountered is the choke housing.
Master, again and still
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Re: Alternative to Using a ThermoQuad
[Re: DaveRS23]
#2660000
05/28/19 01:07 PM
05/28/19 01:07 PM
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Joined: Oct 2008
Posts: 765 Shoreline, Washington
72roadrunnergtx
super stock
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super stock
Joined: Oct 2008
Posts: 765
Shoreline, Washington
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I have some recent experience trying to get a Street Demon 750 to run well on one of my Mopars. The following is my observation/opinions. The motor is a mild build 400, cold Edlebrock performer intake and E-street heads. Out of the box it was jetted pretty close for this combo but accelerator pump didn’t seem to be working correctly. Wound up having to open it up, found small gaps in lip of the acc pump the lip seal and a tear in the Holley umbrella style check valve. After replacing those parts the pump worked better but still needed some larger nozzle tuning to resolve some slight residual hesitation. No trouble height wise as a Thermoquad replacement but required extensive throttle lever modifications to retain the original throttle cable, throttle pressure linkage components, and correct overall geometry. The Mopar throttle pin adaptor designed for the Street Demon and installed on the “universal” throttle lever on the Street Demon, was useless in avoiding the extensive mods. Plumbing for bowl vent and charcoal canister purge are not present, as with most universal aftermarket carbs. Could never get the choke tuned correctly for decent cold start & run. The factory dual snorkel air cleaner had no issues with the choke housing. The documentation that came with Street Demon refers to possible interference with the choke linkage near the air horn and factory style air cleaners. There is nothing the locate, or center, the lower air cleaner other than the air cleaner stud. I could see where the air cleaner could shift out of place and contact the linage. Another irritating issue was the “goggle” valve, secondary throttle blade, binding in its bore requiring excessive throttle pressure to overcome periodically, especially on first use after warm-up. Tried to reseat the throttle blade on its shaft to correct, helped a little but never resolved the issue completely. Overall tolerances of the various components are not anything close to the Thermoquad, when in good shape, or new Holleys, ended up going back to the best Thermoquad I have. While a bit complex by comparison, with parts that are hard to come by now, a correctly tuned Thermoquad, in good shape, is hard to beat for performance and all-around drivability. Holley still does make a spread bore replacement but it’s a 650 CFM vacuum secondary GM replacement design with a universal throttle lever. Ran one of those too, good drivability overall, just not same full throttle punch IMHO. The Mopar specific models are now long out of production. BTW, I have the Street Demon 750 and all the extra tuning parts for it currently are on E-bay should there be someone here who would care to take it on. Priced well below what I have in it. Street Demon 750
Last edited by 72roadrunnergtx; 05/28/19 08:50 PM.
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Re: Alternative to Using a ThermoQuad
[Re: 340clone]
#2660278
05/29/19 11:17 AM
05/29/19 11:17 AM
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Joined: Oct 2008
Posts: 765 Shoreline, Washington
72roadrunnergtx
super stock
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super stock
Joined: Oct 2008
Posts: 765
Shoreline, Washington
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Should be noted too that the Street Demon is not really a Thermoquad replacement as it is a square bore configuration. It likely will not bolt directly on an OE cast iron spread bore manifold, just like the Edelbrock carbs, requires the use of a square bore to spread bore adaptor, that would mean additional height.
Last edited by 72roadrunnergtx; 05/29/19 11:30 AM.
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