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Using a Thermoquad with boost

Paul_G

Paul_G

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Just curious if carbs other than Holley style will work with boost? Edelbrock or even an old Thermoquad?
 
They work with a draw through system, blow through the primaries are fine but the air door is meant to operate on vacuum demand. In that way its kind of similiar to a vac sec holley...it needs vacuum not boost to open the secondaries. But anything is possible. I think it would be hard for it not to bog? We did a thermoquad on a draw through 318 system in the mid 90s... but took out the turbo oil seals eventually, the turbo we ran couldn't handle vacuum. So we went to a blow through holley like most do today.
 
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Yes, TQ’s and ARB/AVS carbs have been used with boost. They used to fully inclose the carb. While the secondary air door on the AFB is normally thought of as vacuum operated, the pressure from above will tip them open when the secondary side opens. Kits for AFB/AVS carbs were made years back.

Honestly, I’m not anHolley guy but this is the place I’d get one. Various companies are around for blow through carb applications.
 
I don't see why you wouldn't use a thermoquad. Mr norms did brand new in 72.
 
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I really think the Holley is the way to go here.

Thanks for the thread link.
 
Like this?

892B639F-5D26-4ACE-90D8-5AEA5CE5510F.jpeg
 
Our turboed 318 first started out with a draw through thermoquad with a Switzer turbo. We had 3.23 and 276/60-15s I remember flooring it with 6 people in the car at 20mph and smoking the tires through first gear. Loved our TQs.
 
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Thanks for all the info. I never thought about fuel being pushed out around the accel pump shaft.

I have a Holley 900 CFM that is a boost carb. It is on the 528ci Hemi right now with a Procharger. The Procharger makes about 10PSI of boost. The Hemi is coming out for a refresh. I want to put a 383 in it's place till the Hemi is done. The big Holley may be too much for the 383. No idea how the 383 will do with that big a carb and 10 psi of boost. I might look around for a 650 Mechanical sec Holley to modify for boost rather than using what I have.
 
While the thermoquad will likely run well under boost in a carb enclosure box, you'd likely need the nitrophyl floats to avoid them being crushed like the hollow brass floats could do.
 
Paul_G said:
Thanks for all the info. I never thought about fuel being pushed out around the accel pump shaft.

I have a Holley 900 CFM that is a boost carb. It is on the 528ci Hemi right now with a Procharger. The Procharger makes about 10PSI of boost. The Hemi is coming out for a refresh. I want to put a 383 in it's place till the Hemi is done. The big Holley may be too much for the 383. No idea how the 383 will do with that big a carb and 10 psi of boost. I might look around for a 650 Mechanical sec Holley to modify for boost rather than using what I have.
Click to expand...
Try the bigger carb first.
Photon440 said:
While the thermoquad will likely run well under boost in a carb enclosure box, you'd likely need the nitrophyl floats to avoid them being crushed like the hollow brass floats could do.
Click to expand...
Do not TQ’s have nitrophyl floats?

Click the link above. The links thread has the builder grafting TQ floats to the AFB.
 
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