Thermoquads

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mshred

mshred

The Green Manalishi
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Hey guys,

its getting close for me to do my engine and tranny and one of the last things i need is a carburetor...I have been thinking of goin with a vs carb, and im really attracted to the idea of a thermoquad....my dad had one tuned real well on his old aspen 340 and he used to get awesome mileage staying out of the secondaries and great power when he got in them...he has a truck thermoquad sitting at home and i was thinking of sending it out to demonsizzler to have him do the street/strip build to it...its a little expensive for me right now, and i wanted to know your opinions on whether or not its worth it or if i just grab a vs holley and rebuild that or just rebuild the thermoquad myself (although i know parts are hard to find)...I also hear that the plastic peice in the body can get too hot and warp, so that has me a little worried as well..demonsizzler looks like he does great work so id be interested to hear anybodys experience with his carbs, especially track wise...just as a little filler info my setup is a 340 with forged internals, .30 overbore with 10.5:1 cr, rpm air gap intake, comp 280 duration 480 lift cam, headers, ported x heads and a 5 speed with 3.91 gears...interested to hear what you guys have to say
 
I've had a carb from him and really like the way it performed. Excellent work.
I have had 1 TQ crack on me and the one draw back to it is there no longer made. So you would need a compatable year TQ to replace a cracked one.

I have ran them for a long time without issue, save the one cracked one. All though a dab of JB weld did fix the crack.

You'll need a adapter for the squarebore intake adding an inch in height. Hood clearance can be a issue.

Any carb you decide to use must be freindly to you and easy to work on. A OOTB Holley AFB/AVS or what ever just needs to be well tuned.
 
rumblefish360 said:
I've had a carb from him and really like the way it performed. Excellent work.
I have had 1 TQ crack on me and the one draw back to it is there no longer made. So you would need a compatable year TQ to replace a cracked one.

I have ran them for a long time without issue, save the one cracked one. All though a dab of JB weld did fix the crack.

You'll need a adapter for the squarebore intake adding an inch in height. Hood clearance can be a issue.

Any carb you decide to use must be freindly to you and easy to work on. A OOTB Holley AFB/AVS or what ever just needs to be well tuned.
Click to expand...

Hey Rob,
good to hear that demonsizzler stuff worked out for you...which rebuild option did you get from him? would the regular street one be fine for my application or would the street/strip rebuild be more suitable (keeping in mind i do plan to add more power to this motor in the nearby future)...how well did that JB weld hold up? lol my dad is pretty good at tuning the thermoquad, so i think he can give me a couple pointers and help me out, but im pretty set on vacuum secondaries and think it would be cool to run a well built tq...and yes i know i will need the adapter, something else i am also thinking of- but I am running a functional dual snorkel scoop, so im hoping that the spacer, intake and carb will clear with the extra clearance from the scoop (though its not much)
 
I was just talking with Demonsizzler on chat last night.
I will be sending him my Thermoquad soon.
I'm currently running an Eddy, but it's just not the same feeling.
The secondaries on the Eddy are tiny compared to the Thermo.

And as far as mileage, I had a '76 Duster 318CI 2bbl, and I was getting better mileage with the Thermoquad on my 340 Duster, of course staying off the WOT.
The only problem I've had with the Thermoquad, was from my lack of driving the car and let it sit. Parts are not as readily available as for a Holley.

Giles
 
Mshred,Moparwedden has a Holley750v.s for sale($150)says he just took it off his car.He,s also in Trenton,Ontario.Search to days posts!Hope this helps.

P.S I,m running the Holley 750 v.s on my 73 Dart Sport 340.I have the 800 Thermoquad on the 66,but I just purchased a Holley 750v.s off of Idrift.It,s going on the 66.Can you tell I like the 750v.s?LOL!They used to put them on factory big blocks!
 
If your interested in the Thermoquad, go for it! I used to use strictly Holleys because that's what my mentors in hot rodding used. Then I decided I should learn how a carburetor works and what it does. I studied up a bit and searched out a guy who was known for making Carters, and even Quadrajunks, run well. When he found out I was willing to step out of the box (the red, white and black box) he was anxious to help me learn. The process of making a Thermoquad work well took me some time as the guy wouldn't tell me what to do, he would only make a few suggestions when he saw I was struggling. But, as a result I can now open up a hood and make whatever brand is under there work reasonably well. Since it sounds like your Dad has some Knowledge of Thermoquads grab up all the learning you can, you will never regret it. And, that Thermoquad WILL work well.
 
No that sounds like a good teach. Good you learned about other carbs. This makes you a better mechanic and well rounded.
 
hey guys thanks for the advice....pettyblu, i thought that carb was mechanical secondaries? isnt 750cfm kinda big for a 340 like mine? Also i know thermoquads came into sizes...which would be more ideal for me? and has anybody ever used the holley reman thermoquads? they are a great price and look like a nice peice in the picture, but id be interested to hear anyone's actual experiences with them
 
well i dug through my dads carb stash and we have two thermoquads...one has the smaller primaries and the other has the bigger ones...the numbers off them read as follows-9137S on the bottom plate for one, and 6550S on the bottom plate for the other...are either of these any good for performance?
 
We had one on a 383 that worked really well,matter of fact we still have that carb now that I think about it. Theres some good info on tuning them and modding them in a book called "how to hot rod a small block mopar" If you want to know more about the book I could snap a pic of the cover or something and post it.
Good luck,
Jr.
 
i thought that carb was mechanical secondaries? isnt 750cfm kinda big for a 340 like mine?
Click to expand...
All Carters are mechanical in there operation, but the air door above it make it operate like a VS carb. The AVS and TQ have spring loaded doors that can be tightened up or loosened.

The bigger TQ can be used with ease and is not to big because the spring loaded secondary door opens apon engine demand, slowly opening so the engine dosen't bog. And if it does bog, tighten up the doors spring.

Generally speaking, there considered a 800 or 850 cfm's.

Thermoquads.com , Demonsizzlers site of carbs and TQ's.
 
rumblefish360 said:
All Carters are mechanical in there operation, but the air door above it make it operate like a VS carb. The AVS and TQ have spring loaded doors that can be tightened up or loosened.

The bigger TQ can be used with ease and is not to big because the spring loaded secondary door opens apon engine demand, slowly opening so the engine dosen't bog. And if it does bog, tighten up the doors spring.

Generally speaking, there considered a 800 or 850 cfm's.

Thermoquads.com , Demonsizzlers site of carbs and TQ's.
Click to expand...

hey rumble thanks for the info, but i was referring to a holley carb that moparwedden has for sale that pettyblue was pointing me towards
 
grimreaper said:
A link with great info on Thermoquads.
http://www.rockcharger.com/tech/vaanth_thermo-quad_guide.txt
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hey man, thanks for the link! now i just need to figure out which one is better to use for my application..one is a 78 auto tranny TQ with the smaller primaries from a 318 (Came off my dads aspen so makes sense) and the other is from an international harvester from 74 with Auto tranny as well as the smaller primaries...gonna have to send demonsizzler an email and go from there
 
I like the ThermoQuad, too, but if you decide to use one I think you'd be happier with a spread-bore manifold rather than trying to adapt a square-bore intake. I tried that with my 360, and it just didn't run very smooth. Poor fuel distribution compared to running a spread-bore. At cruise with constant throttle, you could feel it miss slightly. That went away when I switched to a spread-bore manifold (Edelbrock Performer). Unfortunately, I don't think Edelbrock makes the Air Gap in a spread-bore for the Chrysler small block, do they? If you're going to use a carburetor with those big secondaries, you sure as hell don't want to choke it down with a square-bore intake.
 
mshred said:
...isnt 750cfm kinda big for a 340 like mine?
Click to expand...


Absolutely NOT! A 750 Holley is just what that motor needs. Just stick a Proform main body on it and you’ll be amazed at how much more power you have (versus the Thermoquad)…unless you are just looking for nice stock appearing carb with good throttle response to go cruising around town.
 
Bill Crowell said:
I like the ThermoQuad, too, but if you decide to use one I think you'd be happier with a spread-bore manifold rather than trying to adapt a square-bore intake. I tried that with my 360, and it just didn't run very smooth. Poor fuel distribution compared to running a spread-bore. At cruise with constant throttle, you could feel it miss slightly. That went away when I switched to a spread-bore manifold (Edelbrock Performer). Unfortunately, I don't think Edelbrock makes the Air Gap in a spread-bore for the Chrysler small block, do they? If you're going to use a carburetor with those big secondaries, you sure as hell don't want to choke it down with a square-bore intake.
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you make a very very good point...something i will have to consider since i really dont want to get rid of my manifold
 
flyfish said:
Absolutely NOT! A 750 Holley is just what that motor needs. Just stick a Proform main body on it and you’ll be amazed at how much more power you have (versus the Thermoquad)…unless you are just looking for nice stock appearing carb with good throttle response to go cruising around town.
Click to expand...

Hey man i was looking into those proform main bodies...what about them makes you pick up so much power over the factory holley main body? if i was to use a 750 cfm vs carb and stick a proform main body on would it increase cfm to make power (thus making it like 800 or something) or just increase power while still flowing the same? also, my thinking was that a 750 wouldnt have as good of throttle response as a 650, but i do plan to add more power sometime in the future so i guess maybe getting right once is the better way
 
The 'trick' to making any 4bbl work with an adapter(sq bore to spread bore)is:

a)most adapters require hand grinding to the front and sides of the areas closest to the primary bores,

b)hood clearance between the under side of the hood to the top of the air cleaner,

c)open center gaskets above and below the adapter,

d)lengthen the accelerator cable and re-adjusting the kick-down linkage if running an automatic trans.

It just is not that big a deal. And in many cases, it does help performance, David.

tqon340.JPG


PICT0862.JPG
 
do holley vacuum secondary carbs with metering plates as opposed to metering blocks allow jet changes only though drilling out the metering plates? or do some vs secondary holley have metering blocks for the secondaries as well?
 
The Proform main bodies have sculpted venturis, no choke horn, and adjustable air-bleeds…FWIW, when I bought the main body for my 650 dp carb, I read that you could gain 25-50 hp. I thought “Yeah right”, but I tried it anyway because it was only 99 bucks at the time and it would bump me up to 750 cfm. To my surprise, my car picked up 3 tenths and a little over 3 mph in the ¼ mile right off the bat…that’s probably about 30 hp! Then I started tuning and it just got quicker from there (I carved a couple more tenths off over time).
 
flyfish said:
The Proform main bodies have sculpted venturis, no choke horn, and adjustable air-bleeds…FWIW, when I bought the main body for my 650 dp carb, I read that you could gain 25-50 hp. I thought “Yeah right”, but I tried it anyway because it was only 99 bucks at the time and it would bump me up to 750 cfm. To my surprise, my car picked up 3 tenths and a little over 3 mph in the ¼ mile right off the bat…that’s probably about 30 hp! Then I started tuning and it just got quicker from there (I carved a couple more tenths off over time).
Click to expand...

sweet man! so im assuming that each of the main bodies will increase flow 100cfm? because it doesnt say so on their website...if i was to use one it would be on a vacuum secondary holley though, but im not sure if you can change the jet sizes on a holley metering plate without extensive mods....i guess i would be flowing 850 cfm by adding a proform body to a 750 carb? think that might be overkill though??
 
mshred said:
Hey man i was looking into those proform main bodies...what about them makes you pick up so much power over the factory holley main body? if i was to use a 750 cfm vs carb and stick a proform main body on would it increase cfm to make power (thus making it like 800 or something) or just increase power while still flowing the same? also, my thinking was that a 750 wouldnt have as good of throttle response as a 650, but i do plan to add more power sometime in the future so i guess maybe getting right once is the better way
Click to expand...
Read this article regarding your 340....go big on that carb selection
http://compcams.com/Community/Articles/Details.asp?ID=-738676943
 
demon sizzler said:
The 'trick' to making any 4bbl work with an adapter(sq bore to spread bore)is:

a)most adapters require hand grinding to the front and sides of the areas closest to the primary bores,

b)hood clearance between the under side of the hood to the top of the air cleaner,

c)open center gaskets above and below the adapter,

d)lengthen the accelerator cable and re-adjusting the kick-down linkage if running an automatic trans.

It just is not that big a deal. And in many cases, it does help performance, David.
Click to expand...

I see you also have a notch in the intake itself....what is that for? also, is there a way to increase the cfm of the tq wihtout removing the choke horn?
 
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