Rebuilding ThermoQuads: Who has some helpful tips and advice?

[Kern Dog]

Hello, I have several core ThermoQuad carburetors that are good candidates for rebuilding but I have never actually tried going through them by myself.
I have rebuilt Holleys, mostly the 600 and 750 CFM versions. Holleys are easy for me but that may be because I started out with them way back in the 80s. My red Charger has a Demon 850 which is a Holley based unit.
I used to have a local guy rebuild carburetors for me but I want to do these myself from now on. I have a few cars here that would benefit from a well tuned Thermoquad since they can actually deliver decent mileage as well as make those glorious moaning sounds at WOT.
What tips or suggestions can you offer to help a man have success with these? What brand of rebuild kit is worth a try?

 

[GTX JOHN]

There are several good books on Thermoquads available.

 

[Kern Dog]

If everyone just read books, these forums wouldn't exist. Check back in when you have something worthwhile to add.

 

[GTX JOHN]

The Thermoquads are not intuitive to understand by
just taking them apart. You would be behooved to start
with studying a book despite how smart a mechanic you think you are.
I own well over 100 Thermoquads and have raced them competitively in NHRA for
well over 50 years. I still refer to reference books and specs regularly. If you had a specific
question someone could certainly answer it for you (As would I). In fact, I have
helped many folks on this forum multiple times on these carbs and many other things.

However, there is neither the time nor space on these forums to go through all the
nuisances of preparing these unique pieces for various performance applications.

If you spent a whole day at our shop, I could teach you some of the steps in the rebuilding
and modifications that we perform on these carbs. = But not in a couple paragraphs.

BTW: I was not being a Smart *** but giving you what I sincerely feel is the right way to start on
a rebuild on these. I go on the Forums primarily to try to be a benefit to other people of some of the things
I have learned (Often the hard/expensive way) in my nearly 80 years.

My .02 = For Free!

 

[493 Mike]

TQs are quite easy to work on. I was a line mechanic back when they were used by Chrysler and had schooling on them. The most important thing with any rebuild is to follow the sequence that comes with the kit instructions for adjustments. Be careful of the float bowl, it's fragile and soak it in a good chemical dip. As the feds have taken out the "good stuff" in these dip solutions, I like to give them a overnight bath and have to rinse them in my solvent tank to rid them of the black "soot" that doesn't come off in the dip. Ensure the square O-rings in the main wells are correctly placed upon reassembly. Have fun too!
Mike

 

[Jonas Nordstrom]

As said above about adjustments after the rebuild: Follow the sequence.
If something doesnt add upp, back-track and check again.
Fixing a TQ really means digging into details.

For the rebuild:
-Inspect the plastic body for cracks.
-Inspect the glue on the wells, put some gas in the plastic body, put it on a white paper parallel to ground. If the paper is dry the next day you are good to go.
-Inspect the plastic body flatness. (Make it flatter by carefully grinding it on some sandpaper.)
-Check the Prim throttle shaft for wear. If worn, put in a bushing.
-The small Acc-pump tube from the kits are ok, but weed-hacker fuel lines stays on better.
-Try to find the viton version of the o-rings for the main wells.
-The leather acc pump is better than the plastic one, but dries out fast if the car is not driven often.(Soaks up again quite quickly though.)
-Screw it together in the right sequence and dont overtighten. (30 inch if I remember correctly?)
-Brass floats are nice too.

Have fun and take your time with the adjustments, a TQ is the most complex 4-barrel carb to rebuild/adjust (Oh and well...6-packs.) ...but the reward after when done right is amazing.

I myself just got my TQ unicorn that I am rebuilding now. Cant wait to get home to the garage.

 

[rickseeman]

Sometime within the last year or so someone posted a link to a good paper written by a Thermoquad guru on this forum. I didn't save it because I've never owned a Thermoquad but maybe someone will chime in with it.

 

[kiwigtx]

However, there is neither the time nor space on these forums to go through all the
nuisances of preparing these unique pieces for various performance applications.

I think you meant nuances .....but I catch your drift.

Book are excellent reference material that will last a lifetime...as long as they are authored by knowledgeable people, and not the average shade-tree wannabe.

One of the most common replies people asking technical questions here is - "Buy an FSM" ...seems appropriate here also.

 

[Kern Dog]

To a degree, yes.
I leave room for the possibility that some things become evident 40-50 years after a book was written that may not have been known when the book was published. Some short cuts are discovered, some fixes are found that may be easier than doing what was published before too.
I agree, the books may be excellent for disassembly and reassembly.

 

[rickseeman]

Here is one paper
https://www.forabodiesonly.com/mopar/attachments/a-carter-thermo-quad-guide-pdf.1714667249/

 

[Cranky]

One of the things I 'learnt' with a TQ is not to bead blast the metal parts! lol. It took me awhile to figure one out years ago but finally did and that thing taught me a lot. Yeah, Holley carbs ain't hard at all but the TQ takes a bit more thought and adjusting that air door is another key area. Also, what works on the street may not be optimum on the track. I thought mine was set up quite fine until the car got a set of slicks installed. Another learnt moment The air door wasn't out that much but it was probably worth a tenth maybe.

 

[GTX JOHN]

I think you meant nuances .....but I catch your drift.

Book are excellent reference material that will last a lifetime...as long as they are authored by knowledgeable people, and not the average shade-tree wannabe.

One of the most common replies people asking technical questions here is - "Buy an FSM" ...seems appropriate here also.

Nope.......................Actually meant nuisances.

I know all the nuances!

Old Guys Humor = Sorry!

 

[kiwigtx]

Nope.......................Actually meant nuisances.

I know all the nuances!

Old Guys Humor = Sorry!

 

[oldbee]

Greg, get a TQ manual; internet is all well and good but I love a hard copy in my hands.

 

[Kern Dog]

I do too. A helpful FBBO member stepped up and offered to send me one. Another one offered to chat and walk me though the rebuilds.
I wasn't looking for someone to do it for me, I just wanted to see if anyone had some helpful tips and a few did like .....the air door adjustment, the squarish O rings that have to be properly seated, the leather accelerator pump needing to be soaked in fuel to remain intact...stuff like that. I've read factory service manuals for a variety of things and sometimes they are not as concise or complete as some seem to think. Often times, there is redundant verbiage, areas covered that don't apply or other things that are of no help.

 

[Geoff 2]

As mentioned above, I would get a leather acc pump. I have had the rubber/plastic ones roll the lip over...& no pump shot. You will probably have to buy it separately.

 

[Some Car Guy]

Two screws are kinda hidden, don’t try to force the body apart thinking you’ve got them all out.

An old timer mechanic gave me an air door lock ring tool that slips over your screw driver. Neat, but not necessary. He said he hadn’t used it in 20 years and I was tinkering with mine so he liked to see it used.

 

[Jonas Nordstrom]

When I started TQ I got all the books, service manuals etc etc and studied like crazy.

Though now I would like to have a book named "How to restore a Thermoquad that is 50 years old".
A 50 years old Carter Afb/Avs or Holley is easy, but...

Digging into a 50 years old TQ means that you will have to check the plastic body for hairline cracks.
Sides that have bent outwards cos of age/heat.
Plastic body warpage.
The glued wells coming loose.
The plastic body covered in that black soot that is crazy difficult to get off and makes the gasoline creep up the walls and under the gasket....leaking into your plenum...
Check the surfaces of the top part for flatness where the top meet the prim booster o-rings.
Stick thin metal rods into all tubes to check that nothing is stuck there.
Check shafts for wear and straightness.
And so on.

Also, if you see a non-restored TQ at a swap meet that looks dry and pale, be careful, they are very often corroded to death.
If you see a oily dirty one, almost brown in color, grab it.

 

[Geoff 2]

A good bookm on the TQ which describes how it operates is Carter Carburetors by Dave Emanuel., S-A books, ISBN 0-931472--11-3.

I have had this book many years, not sure if it is still available.

 

[Jonas Nordstrom]

A good bookm on the TQ which describes how it operates is Carter Carburetors by Dave Emanuel., S-A books, ISBN 0-931472--11-3.

I have had this book many years, not sure if it is still available.

Agreed, good book.

The tricky part I think is to find the correct adjustment measurements for a specific TQ #.
For ex, I have the measurements for a Super quad and a 6545...but now I need them for an older type, the 6324.