Mounting Thermoquad to air gap style intake. What adapter?

JoePole1

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I have a 75 850 TQ (larger secondary) that I would like to mount on dual plane square bore intake for my small block 360. Going to be a learning experience including the TQ rebuild. This is strictly a street engine. Hood clearance may be a factor with the tall manifold. For those who have done this, what are you using???
I was thinking of the Mr Gasket 1932 and hog it out if necessary. I did shave down the plenum divider a bit on the intake.

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YY1

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71-74 Chargers are notorious for not having much room for even a taller air cleaner.

I sold a guy a hood that already had the crossmember cut out for his 440 car with IIRC an RPM intake.

His factory hood wouldn't close and he didn't want to cut it.
 
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JoePole1

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72 Satty and small block should give me a little more room. Currently has an edelbrock 1906 600 cfm. I will measure what I have now and add difference with TQ and spacer. Spacer above is .750".
 
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YY1

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Curve of hood is a bit different on Plymouths.

There is about 3/8 inch more room.

This is just from me eyeballing a 73 RR hood I have installed on a 72 Charger.
 

toolmanmike

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I have a 75 850 TQ (larger secondary) that I would like to mount on dual plane square bore intake for my small block 360. Going to be a learning experience including the TQ rebuild. This is strictly a street engine. Hood clearance may be a factor with the tall manifold. For those who have done this, what are you using???
I was thinking of the Mr Gasket 1932 and hog it out if necessary. I did shave down the plenum divider a bit on the intake.

View attachment 1716020170
I think you are on the right track. Smart of you to know there may be some modifying that may need to be done.
 

Rat Bastid

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That adapter (any adapter like that) is a power killer. If you want to run the TQ, get a different manifold.

Again, those things cause more issues than can be fixed.
 

Brooks James

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That adapter (any adapter like that) is a power killer. If you want to run the TQ, get a different manifold.

Again, those things cause more issues than can be fixed.
If it's for a dual plane get one with the bar right down the center, to keep the distribution as close as possible to stock
 

AJ/FormS

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I love TQ's.
I tried the 850 on my 360HO with the AirGap and adapter.
IMO; for street use with street gears, this combo is a waste of time.
I tried several other carbs as well, but I found the 750DP was about the best on my combo, if a little large.

However; that same 850 on a proper small-port 2P intake, is dynomite on my Smog 318.

If you try this, make sure the secondaries don't snag on the adapter, at WOT! That adapter, altho it works, the transition is just too abrupt. Mine needed a thick gasket for secondary clearance.
If I had to guess, that adapted 850 made about the same WOTpower, as my 600 Holley, or the AVS off a 340car(580?).

BTW,
From my research:
Carter carbs are rated differently than Holleys, and because of that, you cannot directly compare an 850TQ (Carter) to an 850 Holley. I thought I used to have a conversion factory in my notes, but can't find it. Going from memory, the 850 TQ compares to a smaller Holley.
Does it matter?
Only if your 360 is a big-cammed, high-compression, free breathing, HotRod engine. The stocke lo-compression 360 can't hardly pull a 500/550 down at WOT.
 

JoePole1

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Maybe I'll look around for a weiand action plus. Would be nice to check operation of the TQ before pulling the manifold. I know they are difficult to dial in especially being a novice.
 

Bewy

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Joe,
Congrats on using the excellent TQ. Use the Holleys as a weight on the trash can lid to stop the wind blowing it away....
You say strictly street use. If usable power is to be 5500 or under, then the Performer is a better choice & no spacer/adapter is reqd. Bolt on deal. Be realistic with the rpm expectations, which will depend on cam & other parts. Nothing to be gained, only losses, fitting a 6500 rpm intake [ the RPM ] on a 5500 rpm engine...
Because the carb pad is lower on the Perf, you may be able to add a 1" spacer [ divided or 4 hole, NOT open ]. This often adds a few upper end hp, with no loss down low. A free lunch...
 

Bodyperson

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I modified an offenhauser to accept a quadrajet. Looked legit. Never did run it though. Just a thought.
 

Brooks James

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Maybe I'll look around for a weiand action plus. Would be nice to check operation of the TQ before pulling the manifold. I know they are difficult to dial in especially being a novice.
You will not regret taking the time to tune a Thermoquad for STREET use
 
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Brooks James

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You will not regret taking the time to tune a Thermoquad for STREET use
I'm setting up a dual TQ set up for a 426 wedge, the Edelbrock 4 hole adapter looks to be the least restrictive and best matching. As you can see here, the adapter positioning will cause uneven flow and turbulence as it hits the metal between the 4 holes using the Mr Gasket adapters .the Edelbrock 4 hole adapter will be a closer match to the existing 4 holes on the intake.
Yes I know that the air gap is not 4 hole but I think it would be the best existing match if you can't find an adapter with a bar down the middle Ithe 4 Edelbrock is $ $33 on Amazon

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RustyRatRod

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The Holley Street Dominator is an excellent choice if you decide to go to another mannyfold. It's a low rise single plane, but gives up nothing on the bottom end and has a spread bore carburetor pad.
 
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