Unusual Intake Manifold for SBC-Thermodyne

Anyone heard of, or familiar with Thermodyne Intakes, I used to see them advertised in some of the rod mags. Seems like they were located in north central Arkansas
Actually the intake in question is aluminum and the full name is "Thermodyne Driver"

 

bttt

 

I did some dyno work with these intakes. They did not deliver as promised and a stock Q-Jet on a factory cast-iron intake did just as good atop a mild SBC.

It was a neat idea. It just didn't work very well.

~Scotch~

 

Scotch, I appreciate the information. What was supposed to be the advantage of the venturis in the port runners. I own one of the intakes and am very curious about it. With the intake came the installation directions and very specific timing information. Did your dyno test follow the timing instructions or did you varie the timing at all during the tests. I'm pretty sure the company is gone but somebody had a fair investment in the tooling etc. Mike -- 41woodie

 

The tubes were supposed to pick up fuel that had puddled under the carb and put it back into the airstream in the intake runners. The idea was interesting, but I questioned from the start about how effective it'd be and exactly how much fuel puddled under the carb. Enough to gather in the little depressions in the floor of the casting? Enough to be drawn through the tube and into the airstream of the port?

So, I discussed it with the creators at Thermodyne and ordered up a matched set from them. This matched set included their carb and intake (jetted to match) and their HEI (curved by them to take advantage of their designs). I wanted to give them every possible benefit of the doubt.

The subject vehicle was a '69 Chevy Suburban. The 350 had recently been rebuilt with a flat-tappet hydraulic RV grind, and had headers. Otherwise, it was a typical flat-top 350 with 1.94/1.50 iron heads. Absolutely typical, and Thermodyne agreed it'd be perfect for the dyno test.

So, we went to chassis dyno and tested the truck with the stock Q-jet and factory intake, and points distributor. We then swapped all the Thermodyne goodies on, and made a pull. There was maybe a 5-horse/5-lb-ft gain around 2,500 rpm. Hardly worth the investment in the intake/carb/distributor.

I called and discussed all this with the creators, and they had no suggestion. I asked how their dyno tests were done, and they finally told me they'd never done any, and had been relying on 'seat of the pants' feel to extoll the virtues of their revolutionary design.

I figured that the small port size in the intake manifold will find a sweet spot around 2,500-3,000 where velocity is really fast (typical with any small-port intake) and after that, it'll start starving for air. The air/fuel mix stays nice because the intake ports in your heads are larger, and the step from the small intake port to the larger cylinder head port keeps the air/fuel mix in suspension nicely.

Otherwise, it's about as good as....a stock Q-jet intake. LOL!

I did not modify the one I had at all. I feel it could have found a few more ponies if the ports were a little bigger, but I wanted to see how it all worked 'out of the box' since the mfr's were talking about it like it was magic. I don't believe in magic, so I didn't touch it and I followed their recommendations to the letter. If they were on to something, I wanted to learn it.

Sadly, they were not. I've concluded the little tubes are useless unless you've got a float stuck or something.

I applaud their experimenting with a new idea and honestly, the intake casting was of high quality. They were serious and did not cut corners with the mfg. However, like many new ideas, it simply did not work. This all happened in the summer of '98.

~Scotch~

 

Scotch, I really appreciate the detailed information about the Thermodyne set-up. I've never seen a set other than the one I own. I could never get a mental grip on what the venturis were supposed to do for the mixture but I'm certainly no expert. Like you I would think that the small runners would help throttle response but there are other manifolds around with similar small port design that could do the same for less money.
I'm going to run mine on my 41 Ford Woodie just because I have it and it's something different to mess with. The 350 is running a mild dual pattern Comp Cam (as suggested by Thermodyne), roller rockers, balance job, sealed power rings etc. Nothing much beyond stock but it ought to pull the weight of the station wagon around better than the original flathead. Thanks again for the information it was much more than I expected to find out. Mike H. 41Woodie

 

pictures?

 

Miles, what would you like pictures of? I have the manifold off the engine for a few days having screw in rocker studs installedin the heads. Be glad to shoot whatever you want to see. Mine has been powder-coated black but was originally cast aluminum. Let me know

 

i'd like to see the intake too!

 

Any pic would be good as I have not seen one before.
Thanks

 

Yeah, i'd like to see it too

 

Where else but the HAMB are you going to find not only a guy with this incredibly obscure intake, but another guy who actually did dyno testing on it?

-Abone.

 

AAND, neither has a picture for us

 

Scotch, Can you explain the theory of the intake a bit more?

I'm not sure I understand...

The runners are smaller to get the speed up but that doesnt speed up the mixture onder the carb, does it?
( where it will puddle, if it is going to )

How hard was it to jet the carb?

I used a ( badly disigned ) intake once on a hot 4cyl, that had a restriction in it.
It was a bitch to get the carb dialed in ( 40DCOE Weber ).
It seemed to me that the extra " venturi " just killed the signal the carb needed...

 

What they said.

 

I'm not some expert. But i think the venturi should be left in the carb where it belongs. If it was that good an idea, it'd still be practiced

 

It wanted to work...but the stock Q-jet wasn't bad either! I think the Q-jet was 800cfm, and it had been recently rebuilt and was in fine working order...which showed! It's a good choice for such an engine.

The mfr wondered if we'd see more improvement with a 383 or larger engine that could take advantage of the additional carb, or if more cam and rpm would show an advantage. The test car they developed all of this on was a Corvette with a 383 and more cam, so that was the reference. But...it would have had to make a significant difference over a wide rpm range to justify the cost- especially when compared to a comparable Edelbrock Performer or Holley Avenger package. It just didn't deliver as much as they hoped.

~Scotch~

 

Ok guys, I don't know how to insert photos directly so I'm putting several links leading to photos of the intake manifold being discussed. The particular part of this intake is the venturis that are visible in the throat of the ports. If anyone wants to take the time to insert the pictures into a post I'd appreciate. I really would like to hear discussion of this intake.
http://www.members.cox.net/sooner-356ea/Thermodyne.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne2.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne3.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne4.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne6.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne7.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne8.JPG
http://www.members.cox.net/sooner-356ea/Thermodyne9.JPG

 

As further explaination, the venturis visible in the pictures are at the end of tubes that run through the body of the manifold and originate in the floor of the area of the manifold directly beneath the carb. I guess the idea is that the airflow will create a vacuum in the venturis that will scavenge puddling gas from the area under the carb.

 

Definately an interesting intake! Thanks for the pics. The ports look like an oval port big block Chevy. What era's that from?

 

Thank you Scotch.


BTW, those pics look way different than I thought they would.

I thought it would just be a reduction in the runners, but there is a whole lot of extra plumbing going on...

So they created a high speed/ low press situation in the ports and connected them to the floor of the plenum?
That makes more sense.

 

'97-'98.

 

If what passes for my memory is correct I purchased the intake in the mid to late 90's. I'm going to go ahead and run it, maybe no better than stock but I like weird stuff.

 

Well shit, i've never seen or heard of it. So, i thought it might've been older. Let us know what you think of it

 

anyone still wandering about these intakes?

 

Never seen one of those.Thanks for posting this!

 

I remember when I was a kid in the 80s my dad having a thermodyne sticker on one of his tool boxes,what else did they make?Im suprised that that one came out in the 90's i would have never guessed that!

 

Well, here it is July 2022, I just bought one of these intakes. I’m gonna put it on a 283, aluminum TFS 175 heads and see what happens. I’m not looking for anything spectacular, it’s in the wife’s 1957 Volvo Duett. But what the heck, try anything once right?

 

Could you post a pic looking down the throat of the manifold? I can't picture it. Thanks.