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Who rebuilds/modifies Thermoquads?

General engine tech -- Drag Racing to Circle Track

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quickd100
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Re: Who rebuilds/modifies Thermoquads?

Post by quickd100 »

The competition series were 1000 and 850 cfm. The standard production models were rated at 800 and 850.
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hysteric
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Re: Who rebuilds/modifies Thermoquads?

Post by hysteric »

Sonofthatguy wrote: Sat Aug 22, 2020 1:30 am I was helping my nephew do a school project about our family history when we came across this old thread. I was shocked to see that guys still talk about the Carter Thermoquad. I hope you still find it of interest. I grew up hearing my dad talk about it constantly and spent many evening and weekend hours watching him work on it and many other carbs. Those carbs were his life. I always hated when he left to go spend weeks in the Arizona desert testing them. But then he put it in Carter's dragster which I got to see and I was a very excited kid. You see...my dad was the lead design engineer for Carter all of my childhood. He always said the thermoquad was his greatest design. He's 90 now, still has his health, and still living in St. Louis. When I told him about you guys and that I was going to post here he asked me not to. He's a very humble man. So I won't mention his name. He told me he still has the thermoquad prototype (the first one ever built). If you have questions for him I will pass them along and give you his answers. But I'm not sure how much he will remember. It's a shame that engineers rarely get credit for their designs. Through Carter he has 105 patented designs.
Please thank your father for me!
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Re: Who rebuilds/modifies Thermoquads?

Post by hysteric »

raynorshine wrote: Sat Aug 22, 2020 2:26 am
andyf wrote: Wed May 09, 2018 12:23 pm
70GS455 wrote: Mon May 07, 2018 12:29 pm Since I have not been able to contact DemonSizzler, does anyone know who can rebuild and modify for performance a Carter Thermoquad?
I have a TQuad that Demon Sizzler rebuilt and tuned a few years back. I never used it so it is still ready to go in the box. I'll sell it if you need one. I took it to a swap meet and had a $50 price tag on it and nobody was interested so they must not be worth much.
when so many people approve, you should re=think things....best factory carb ever produced for small blocks.. :idea:
Too late he sold it me and boy does it run.
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Re: Who rebuilds/modifies Thermoquads?

Post by mag2555 »

I ran a TQ on a motor of mine for many years and it was very nice, but the long term issue that you can't get around is that of its plastic fuel bowl!

They out gas, as any plastic does and with heat and time dry out loose there flexibility and warp and or crack, and then your up that smelly creek without a paddle !!

If you have a original good one now or a new one that will be run on a unheated by Exh intake manifold then you will probably be fine for a long time, however if you are bolting it on a motor that must Exh thru cats , then for me all bets are off!
quickd100
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Re: Who rebuilds/modifies Thermoquads?

Post by quickd100 »

There are 2 common issues with them. The plastic wells under the primary jets are glued to the plastic center section. The glue gets old and doesn't like ethanol blended fuel. Marine Tex solves that problem. The other problem is the 2 rubber O-rings in the center section, they dry out, shrink, break and need to be serviced now and then.
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Jeff Lee
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Re: Who rebuilds/modifies Thermoquads?

Post by Jeff Lee »

I used to run TQ’s in the late ’70’s, mid 80’s. During that time, if you bought one a a swap meet and it didn’t run good, most all problems were solved by purchasing a “bowl kit” which was a new bowl, gaskets and o-rings. It was about $23 back then! I don’t know if they are even available anymore?
A TQ was good for any 340 or even 440 and you could even get decent gas mileage.
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Re: Who rebuilds/modifies Thermoquads?

Post by Tuner »

Sonofthatguy wrote: Sat Aug 22, 2020 1:30 am I was helping my nephew do a school project about our family history when we came across this old thread. I was shocked to see that guys still talk about the Carter Thermoquad. I hope you still find it of interest. I grew up hearing my dad talk about it constantly and spent many evening and weekend hours watching him work on it and many other carbs. Those carbs were his life. I always hated when he left to go spend weeks in the Arizona desert testing them. But then he put it in Carter's dragster which I got to see and I was a very excited kid. You see...my dad was the lead design engineer for Carter all of my childhood. He always said the thermoquad was his greatest design. He's 90 now, still has his health, and still living in St. Louis. When I told him about you guys and that I was going to post here he asked me not to. He's a very humble man. So I won't mention his name. He told me he still has the thermoquad prototype (the first one ever built). If you have questions for him I will pass them along and give you his answers. But I'm not sure how much he will remember. It's a shame that engineers rarely get credit for their designs. Through Carter he has 105 patented designs.
Would you please ask him about the T-Quad secondary main jet, main well, and air bleed emulsion tube.

I will describe a jet I have here to establish the reasoning for the questions.

The T-Quad secondary jet is a 1.580” long, stepped brass tube, .315” and .375” OD, with 5/16” NF thread on one end and the metering orifice in the tip of the other end.

The preponderance of the length of the inside diameter of the Main Jet tube comprises a Main Well which encloses the combination Air Bleed / Emulsion Tube.

The Air Bleed / Emulsion Tube projects about 1” into the ID of the combined main-jet/main-well and has two .033” bleed holes located about 1/2” deep into the tube from the sealing flange at the threads.

The inside diameter of the jet/well tube is stepped and is .201” ID above the jet orifice and .213” ID above a step which is about .560” down the tube from the threaded end.

The question is about the effect of the inside diameter of the Main Well and the vertical location of the step relative to the vertical location of the orifices in the air bleed tube.

To adjust or correct the A/F over a wide range of air flow, from minimum to maximum RPM, what effect can be obtained from changing the jet/well tube inside diameter and step location?

What effect does the ID of the Main Well have on the overall metering?

Does the volume of the well have significant effect on acceleration enrichment when the secondary is first opened?

Thanks to both of you for this wonderful opportunity to learn from someone who is truly an expert in the carburetor art.
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Re: Who rebuilds/modifies Thermoquads?

Post by Geoff2 »

I have a couple of questions about the production TQs. These used discharge tubes in the sec bores, like the QJ. Instead of the discharge being open like the QJ, the TQ tubes had a bullet shaped nose with a small hole in it; along the length of the tube were 3-5 holes of different diameters; the number, size & spacing of the holes varied for the engine the carb was used on.
Does anybody know the theory/operation of these holes? What happens if you block, add more or enlarge existing holes?

TIA.
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Re: Who rebuilds/modifies Thermoquads?

Post by Tuner »

I hope we haven't missed the opportunity to have our questions answered.
Geoff2 wrote: Mon Aug 31, 2020 5:32 am I have a couple of questions about the production TQs. These used discharge tubes in the sec bores, like the QJ. Instead of the discharge being open like the QJ, the TQ tubes had a bullet shaped nose with a small hole in it; along the length of the tube were 3-5 holes of different diameters; the number, size & spacing of the holes varied for the engine the carb was used on.
Does anybody know the theory/operation of these holes? What happens if you block, add more or enlarge existing holes?

TIA.
Geoff, have you seen the carb jetting instructions in the big Mopar engine book? There are tuning tips for several Thermoquad carb/manifold/engine configurations that mention specific carb part numbers and spray bar discharge hole arrangements. The purpose is obviously for A/F distribution correction for a specific engine combination.

Hopefully Sonofthatguy's grandad can elaborate on why which hole location goes where.
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Re: Who rebuilds/modifies Thermoquads?

Post by Walter R. Malik »

Tuner wrote: Fri Aug 28, 2020 12:06 pm

I will describe a jet I have here to establish the reasoning for the questions.

The T-Quad secondary jet is a 1.580” long, stepped brass tube, .315” and .375” OD, with 5/16” NF thread on one end and the metering orifice in the tip of the other end.

The preponderance of the length of the inside diameter of the Main Jet tube comprises a Main Well which encloses the combination Air Bleed / Emulsion Tube.

The Air Bleed / Emulsion Tube projects about 1” into the ID of the combined main-jet/main-well and has two .033” bleed holes located about 1/2” deep into the tube from the sealing flange at the threads.

The inside diameter of the jet/well tube is stepped and is .201” ID above the jet orifice and .213” ID above a step which is about .560” down the tube from the threaded end.

The question is about the effect of the inside diameter of the Main Well and the vertical location of the step relative to the vertical location of the orifices in the air bleed tube.

To adjust or correct the A/F over a wide range of air flow, from minimum to maximum RPM, what effect can be obtained from changing the jet/well tube inside diameter and step location?

What effect does the ID of the Main Well have on the overall metering?

Does the volume of the well have significant effect on acceleration enrichment when the secondary is first opened?

Thanks to both of you for this wonderful opportunity to learn from someone who is truly an expert in the carburetor art.
O.E.M. ThermoQuads and Carter Competition ThermoQuads have quite different type jets which are in differing places within the carburetor.
For the O.E.M. type ThermoQuads used for racing I make things simple to change jetting by using Holley jets.

Just tap the primary to a 1/4-28 is all for the primary then use a #70 Holley jet with no metering rods.

The secondary is a bit trickier. Shorten the long jet by .240" and drill it through with a .213"/#3 drill. Now tap it to 1/4-28 and use about a #105 Holley jet. Shorten the emulsion tube/air bleed .250"and solder or epoxy the open tip closed. There will be almost no step except at the ending of the jet.

There are a few other changes made but, these are the ones which help with the mixture ratio the most.

Now for Super Stock racing it becomes easily tune-able.
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Re: Who rebuilds/modifies Thermoquads?

Post by Geoff2 »

Tuner,
Yes I have the Mopar book. But have not found an explanation for the whys & wherefores for hole positions & hole sizes in the sec nozzle bars.
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Re: Who rebuilds/modifies Thermoquads?

Post by Tuner »

Geoff2 wrote: Mon Sep 07, 2020 5:33 am Tuner,
Yes I have the Mopar book. But have not found an explanation for the whys & wherefores for hole positions & hole sizes in the sec nozzle bars.
I figured you knew of that information. It follows logic that a person would use EGT and WBO2 and a lot of dyno time. I have played the tie-wrap spivy game on Holley boosters with great success in achieving nearly ideal WOT distribution, but that is somewhat predictable in that the fuel goes where you point the spivy. The spray bar hole locations would probably become likewise logical after a few times at bat to see the outcome of moving the hole locations and sizes around.

I hope we can have a dialog with the gentleman. I would like to know some of his patent numbers to see what he accomplished.
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Re: Who rebuilds/modifies Thermoquads?

Post by Kingbee »

Tuner wrote: Sun Sep 06, 2020 10:03 am I hope we haven't missed the opportunity to have our questions answered.
Geoff2 wrote: Mon Aug 31, 2020 5:32 am I have a couple of questions about the production TQs. These used discharge tubes in the sec bores, like the QJ. Instead of the discharge being open like the QJ, the TQ tubes had a bullet shaped nose with a small hole in it; along the length of the tube were 3-5 holes of different diameters; the number, size & spacing of the holes varied for the engine the carb was used on.
Does anybody know the theory/operation of these holes? What happens if you block, add more or enlarge existing holes?

TIA.
Geoff, have you seen the carb jetting instructions in the big Mopar engine book? There are tuning tips for several Thermoquad carb/manifold/engine configurations that mention specific carb part numbers and spray bar discharge hole arrangements. The purpose is obviously for A/F distribution correction for a specific engine combination.

Hopefully Sonofthatguy's grandad can elaborate on why which hole location goes where.
Tuner, I have the 8th edition of the Mopar engine book but haven’t found the spray bar arrangement you speak of in the Thermoquad section. What edition is your book? Thanks!
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Re: Who rebuilds/modifies Thermoquads?

Post by hysteric »

Might this be what you gentlemen are referring to:

http://www.moparts.org/Tech/Archive/fue ... 9,carb.JPG

Note: "Drill center hole in each secondary nozzle bar to .101

Image
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Re: Who rebuilds/modifies Thermoquads?

Post by Tuner »

Yes hysteric, that is the good stuff from way back in the good old days. That image and others similar are in the MOPAR literature. I guess we missed the chance to have dialog with the gentleman. darn
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