Using a Thermoquad with boost

[Paul_G]

Just curious if carbs other than Holley style will work with boost? Edelbrock or even an old Thermoquad?

 

[Curiousyellow71]

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.

 

[rumblefish360]

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.

 

[RemCharger]

I don't see why you wouldn't use a thermoquad. Mr norms did brand new in 72.

 

[rumblefish360]

I don't see why you wouldn't use a thermoquad. Mr norms did brand new in 72.

Ultimately speaking, the ability to tune it to the 9’s and beyond.

 

[RemCharger]

Ultimately speaking, the ability to tune it to the 9’s and beyond.

Maybe move up to a pair of them?

 

[rumblefish360]

Maybe move up to a pair of them?

I don’t understand, a pair of what. Boobies?!?!?!
I’m game for that, a set for you, a set for me.

 

[Curiousyellow71]

Here is a thread for a boosted afb. I still would do a double pumper. Edelbrock AFB blow thru modifications- pics - vid

And another thread...mention the TQ blowing the plastic out at 18 psi and a visit from fire department...so I was not correct on the air door...the vac sec holley is a fail though.
Boosting an edelbrock carb question - Don Terrill’s Speed-Talk

 

[rumblefish360]

I really think the Holley is the way to go here.

Thanks for the thread link.

 

[RemCharger]

I don’t understand, a pair of what. Boobies?!?!?!
I’m game for that, a set for you, a set for me.

A pair of ThermoBoobs!!

 

[rumblefish360]

Like this?

 

[Curiousyellow71]

Like this?

View attachment 1335199

Nice pair.

 

[Curiousyellow71]

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.

 

[RemCharger]

Like this?

View attachment 1335199

There was a guy on moparts that ran them on a hemi truck if I recall

 

[rumblefish360]

There was a guy on moparts that ran them on a hemi truck if I recall

D100 IIRC. We have spoken with each other.

 

[rumblefish360]

I need my W2’s ported like in post #20 in this thread below;
Power guess on a new combo

 

[Paul_G]

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.

 

[Photon440]

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.

 

[rumblefish360]

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.

Try the bigger carb first.

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.

Do not TQ’s have nitrophyl floats?

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

 

[Paul_G]

Try the bigger carb first.

Do not TQ’s have nitrophyl floats?

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

Yes they do have nitrophyl floats in them.