Thermoquad vs square bore

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71duster06

71duster06

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Im debating between a built thermoquad from www.thermoquads.com the street/strip carb that claims to give 25-30 HP over stock. i would get an alum. performer intake from edlebrock or the arction intake from weiand.

OR the edlebrock performer RPM air gap with a good holley carb.

My motor is a 1970 340, 10.5-1, cam, headers, elec. ignition, head work, complete rebuild. Its in a 1971 duster 4-speed. If anyone has input on what will produce better performance let me know. its a weekend driver that goes to the track sometimes. I love the kick of the thermoquad but i want the best times too.
 
71duster06 said:
Im debating between a built thermoquad from www.thermoquad.com the street/strip carb that claims to give 25-30 HP over stock. i would get an alum. performer intake from edlebrock or the arction intake from weiand.

OR the edlebrock performer RPM air gap with a good holley carb.

My motor is a 1970 340, 10.5-1, cam, headers, elec. ignition, head work, complete rebuild. Its in a 1971 duster 4-speed. If anyone has input on what will produce better performance let me know. its a weekend driver that goes to the track sometimes. I love the kick of the thermoquad but i want the best times too.
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Definetely go with the performer RPM and either a 750 Holley or Demon. I never had much luck with Thermos and with the set it and forget it qualities of the Holley and Demon that's the direction I've taken in last few years.

Terry
 
i was actually wondering about you car times. mine has an 8-3/4 read with 3:91 Posi, BFG T/As 275-60-15, 3100 lbs
 
71duster, do they actually ahve T-quads available? I took a quick look and besides being a mainly GM carb biz, they offer an "aluminum Quadrajet to replace that problem Thermoquad."

You ay also want to check out: thecarbshop.com in Costa Mesa, CA. I have heard some really good things about their TQ work. I think at one time they were reproducing the TQ resin bodies (which had a tendency to warp over time). Re: your main question. I love TQs when they are set up correctly and if modified, I believe they can run just as fast as a Holley. Don't get me wrong, I love both and run both types.
 
thermo quads run fine when the secondary air door is set properly,,,and its not hard to do,,,,most people dont like them because they no nothing about a carb and how the therm quad works,,,i didnt know any one had rebuilts,,intresting i ran one years ago on a 340 and a 400 in a road runner,,, good mileage also when just cruising,,, small primarys,,,just my opinion
 
71duster06 said:
i was actually wondering about you car times. mine has an 8-3/4 read with 3:91 Posi, BFG T/As 275-60-15, 3100 lbs
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Actually my times sucked. With BF banana skins and 30 feet of rubber they were 13.7 and 13.8 (just finished the car 2 yrs ago). Got a set of ET street stickies for it last year but haven't tryed them out yet. I'm using the 8 3/4 with 3.91's also. I'm also looking at getting some times with the existing Weiand single plane that's on it then switching to a Performer RPM and getting some more times.

Terry
 
My last car had a built thermoquad on it. I never got to drive it though. My Dart will also have a Thermoquad on it.
 
I've tried running square-bore carbs and Performer RPM manifolds on two different 360s, one with 8.2:1 compression and the other with 10.5:1. They just didn't run smoothly at constant throttle, and they didn't idle too well. I finally had to conclude that the fuel distribution was lousy. So I switched to TQs and the Performer spread-bore manifold, with no other changes, and like the way they run a lot better. Very smooth at constant throttle and a smoother idle, indicating to me that the fuel distribution is good.
 
GTXperience said:
71duster, do they actually ahve T-quads available? I took a quick look and besides being a mainly GM carb biz, they offer an "aluminum Quadrajet to replace that problem Thermoquad."
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Not sure what you are referring to, because that site is all mopar and all thermoquads.

I had them rebuild a TQ for me after I gave him my engine build specs. Before that, I had a brand new Holley 670 Street Avenger on my 360, and I HATED it. It idled like crap and I could never get it tuned up right. I bolted the TQ up right out of the box and haven't had to play with it since. Definite performance increase over the Holley, and purrs like a kitten at idle. I would recommed Thermoquads.com 100% - he actually posts here under the name Demonsizzler. He knows everything about TQs - you should pick his brain.

As far as your intake choice - The Performer RPM and Air Gap only mount squarebore carbs, so you'd need an adapter or a different intake. My 360 was originally in my truck with a stock iron spreadbore intake, but I'm now going to use a Edelbrock LD340 modified for a spreadbore - so no need for adapters, and from what I've read, should perform pretty darn close to the RPM manifolds.
 
Everyone has a problem with one carb or another. What really needs to be done is learn the carb and stick with it for a few. Just don't get pissed off and throw it away. Each carb maker has a bennifit to it over anothers.

The one thing that grabs my short hairs about the T-Q is the W.O.T. sound and KICK you get from it...the other short hair grab is parts are not at the coner store like a Holley.
Don't fret about the fuel bowl warpping or cracking. Just handle with care and do not over tighten the carb or over heat it. You'll be good.

First picture is a modded LD340 and the next picture is a Holley Street Dom. I forgot to mention in your other post.
On the LD-340, you need not mill the center divider down like I did to make the T-Q fit.

100_0863.JPG


100_0441.jpg
 
I had problems with my Thermoquad, when I first bought the car.
I really didn't like it, constantly bogging. This was mostly due to the car being rarely driven.
So I paid some good money to have a local speedshop rebuild it for me, then I really "Hated" it, so I took it off and took it apart, with the help of a manual I rebuilt it myself.
That's when I discovered how the vacuum secondaries worked, and how to adjust them.

Now I would have to say, it's the best carb I've ever had.
 
What about the Weiand Stealth Intake. From the pictures, it looks identical to the LD340. The shelf has extra meat near the back and has area near the bolt holes for new ones. A lot of people like this intake over the performer RPM but i havnt seen any modified to fit a thermoquad. and yes the secondary kick of the thermoquad is a thing of beauty

http://holley.com/8022.asp
 
Thank you much. I really like Thermoquads and i think i might try the Stealth and have the top shaved to match that of the Action-Plus. For some reason the Stealth has better stats than the Action-Plus. Well see i guess...
 
I gotta be honest, they look like the same damn intake minus the pad and lack of carb stud mounting choices for a Carter carb.

IMO, I'd do a action plus and be done with it! Not to mention a bit cheaper as well. It's the best dual plane out there as cast for a T-Q on a bigger engine unless you need a single plane intake for some high end power. Then it's the M-1's turn.
 
OH, I also want to add, though I've never own a Action plus, being a dual plane intake of a high rise fashion, it should do very well comparably next to a modified LD340. The LD-340 is no longer made and found cheap by compare. Modiefying it to work with a T-Q is easy. But if you didn't have tools to do it and just wanted a OOTB intake that will do well, if not as exactly well, get the Action plus. I don't see a single reason why it wouldn't perform well.
 
yeah i was going to call holley tomorrow and ask about the difference between the Stealth and Action Plus..other than the carb pad..there must be some difference between the two since one is rated for 800 RPMs higher...and ive read about each and people overwelmingly like the stealth..ill let you know tomorrow when i find out
 
I used to pull off perfectly good Thermoquads to replace with Holleys. Why? Because I knew how to tune Holleys. I now pull off perfectly good Holleys and put on Thermoquads. Why? Because I learned more about carburetors. Now I can reasonably tune both. Run whatever you are comfortable working with.....then experiment with another. After all...learning is fun!
 
rumblefish360 said:
I gotta be honest, they look like the same damn intake minus the pad and lack of carb stud mounting choices for a Carter carb.

I just got off the phone with a Holley tech and he said the Stealth and Action-Plus are the same identical intake. The Stealth tho has longer internal runners which get that extra 800 RPMs but the carb pad is identical. Im about 100% sure that i will go with the Stealth and have it machined to match the cutout of the Action-Plus....
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So you need the extra 800 rpm's?

Identical except the runners are longer? Then there...faternal twins right.

This fish smells something rotten and I aint fartin.
 
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