Thermoquad question

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very good carb, easy to tune, we run one on a 340 stocker, only jetting done is opening or closing air door for a/f mixture. they will pass 750 cfm.
 
Best street or street/strip catb you can get in my opinion. Tunes differently than a holley though.
 
Baby huey said:
Looking for input about a thermoquad carb. Good carb? etc??
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Great Carb, but you must be patient and willing to learn.
I had the luxury of an older guy show me how to set them up.
The thing you do is use JB Weld Marine on the well transfer cups at the bottom of the body.

You need to adjust everything in the order of the service manual for initial use.
They need fuel pumps with6 lbs or less of fuel pressure
But once you get a base tune you can customize it to your car immensely since you can change all 4 jets, the 2 metering rods, how much the secondary door opens, how far the tree sits at cruise and idle and how much squirt from accelator pump.
I have 2 of them for my 340 one 800 and one 850, runs better with 850. I can leave my car for a week and it starts on the 1st crank. I added the electric choke helper and it comes off fast idle quickly.
And it sounds glorious at WOT.
 
They are real bad, and I think you should send yours to me for proper disposal.
 
G70464 said:
And it sounds glorious at WOT.
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I stuck one on a 318 and I liked the sound so much that I swapped in some 2.76s into the back, and a 2800TC, with a manual shift. Now, when I floor it in drive, I can listen to the moan for like 23 seconds, until she hits 70mph@ still at 2800 booya! Ok 23 seconds might be an exaggeration, lol.
 
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Baby huey said:
Looking for input about a thermoquad carb. Good carb? etc??
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First, I’ll talk about the bad. Jets and rods are not sold in kits anymore and the ones found on E-bay are expensive as heck. The Carbshop has parts for these carbs. Tuning them is a learning curve. You’ll need to find one that has good throttle shafts, as in not leaking air. Cracked center sections can be JB welded but new ones are about at a zero. Remember there are 2 screws in the primary side of the air horn.

The weird…. Air cleaner bases might not clear so easy. This is due to the top of the aluminum part of the carb having a weird bulge not found elsewhere. The solution is a much thicker carb gasket.

Also, use a thick crab to intake gasket. The rebuild kits normally have this OE style of gasket. The thin paper ones are not helpful and allow to much heat to the carb which will boil the fuel and potentially warp the plastic of the carpet.

The best part

This carbs are generally inexpensive and perform reallllly well. They come in two sizes. For your 273, find a small primary carb. (1.38) The smaller primary will help with air velocity and atomizing the fuel.

Contact GTXjohn for an electric choke model. That ought to simplify installation and speed up the process of getting the car running and driving.

If you get one elsewhere, the less vacuum ports on the carb the better. IE, earlier the year the better.

Take note that the race versions (rarely seen) and the first OE years are entered differently and use press in, not screw in jets. This can be a problem tuning wise.
 
Tell me more about this "electric choke" version. Is there a mod kit available for non-EGR manifolds?
 
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Captainkirk said:
Tell me more about this "electric choke" version. Is there a mod kit available for non-EGR manifolds?
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The aftermarket Carter TQ was available in one size, the small -.38 primary size. They all had electric chokes. Available with a Chevy or Chrysler throttle arm.

A mod kit for the egr is to disconnect the vacuum line to the egr valve. The carb has no hook up for it. You can also fashion a metal plate to cover the egr valve on the intake. Seek the correct high temp gasket for it.

If the floor of the plenum is what you seek a mod in, pipe plugs should do the trick on many intakes. Some have only a untapped hole. Drill and tap or block off the passage from the head to the intake with sheet metal.
 
Baby huey said:
Looking for input about a thermoquad carb. Good carb? etc??
Click to expand...
Not all of them are great carbs. I've found the 72 to 74 are the best. There are some later non-leanburn versions out there too. Many years ago I tried running a later 400 carb on my 360 fury. It was lean and just didn't make the power. I swapped to a 73 440 thermoquad and the difference was substantial. I think they're great but the plastic bodies are going bad on most of mine. They're just getting old.
 
They're called by many names grasshopper Mr ugly, old black magic, bottom line is they are one of the best street strip carbs available. But if you just want to slap something on that runs good and hit the easy button it may not be your best option.
 
This is why I caution people on there use with the phrases, Tuning kits are stupid expensive, jets and rods are hard to find, try the carbshop…. Bowls are available pretty much as only a used code item.

Is it worth it? I think so but the travel time from purchase to dialed in may be a bit longer to obtain due to tuning parts. A small learning curve is involved with them. Also getting a good carb that’s not flat worn out is a plus. You have to learn the carb and mess with everything on it to better understand it or get it where you want.

I’m by all means no expert and have had my days where I ripped them off the car in frustration.
 
Yeah... They are good. A good chunk of their design was utilized in the newer Street Demon carbs.
That says a lot.
One of my fondest childhood memories is my dad gunning the old Ramcharger whenever he needed to pass cars. That roar that thermoquad emitted was unique, no other carb did that. Not even the new Street Demons, I mean they do slightly, they're just too... "tame"
 
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