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Another round of dyno testing with the Thermoquad

7

70GS455

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After finally recovering from major engine damage when the motor swallowed a screw, I was finally able to resume testing. I tried 4 carbs, here are the best 2: a modified 6322 850 Thermoquad and a 0-80805BK Holley 950 Ultra HP (this is the 1.60" venturi version so it's a true 950). Both were fat to be on the safe side and the Tquad was the richest of all so actually there are probably at least 6 to 8 more numbers in it.

The secondary configuration is: stock HSB/emulsion orifice at 0.035", air door at 0.900" to the back bore, 0.143" jets, 90 degree butterflies, spray nozzles with a big .125" hole in the ends.

As part of the testing I wanted to characterize power vs door opening. This is what I found:
Door HP
.750 595
.800 604
.850 609
.900 617

The Holley was 611 hp, 621 ft lb, the Tquad 617 HP, 620 ft lb.

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And forgot to mention that the TQuad has had the primary venturis removed from the plastic bowl, still retains both boosters
 
70GS455 said:
And forgot to mention that the TQuad has had the primary venturis removed from the plastic bowl, still retains both boosters
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So what's the resulting increase in airflow from that mod?
 
Doorkicker said:
Can you share the engine specs? It would be fun to compare.
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This is on a GM product so go easy on me lol. BBB, 482, ported AL heads flowing 330 CFM, ported Edel dual plane intake, 236/244 hyd roller, 10.9 CR, 93 pump gas. Nothing exotic, typical street/strip
 
70GS455 said:
This is on a GM product so go easy on me lol. BBB, 482, ported AL heads flowing 330 CFM, ported Edel dual plane intake, 236/244 hyd roller, 10.9 CR, 93 pump gas. Nothing exotic, typical street/strip
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That combo sounds like fun. A lot of us on this site have other brands or have owned them. As a teenager, the first car engine I overhauled was a 350 Buick for my cousin. It still runs today. Hate to think how long ago that was!
We have a 1000cfm competion thermoquad on our 542. Also have the same TQ you ran.
Do you have pictures of what you modified on your TQ?
 
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A 1000 CS would be the way to go for max power. How are they to tune?

As far as external mods, other than the primary venturis, I added an adjustment screw for the air door, drilled the ends of the secondary discharge tubes a little bit bigger than the Mopar tech paper, and smoothed some of the rough edges surrounding the pri and sec bores

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GS, in reference to post #8, I meant the primary venturiis. Did you test with the venturiis in place, & then removed?
 
GS, referencing post #11. The pic showing the sec jets. Did you enlarge the openings slightly?

I would solder shut the holes along the secondary discharge tubes & angle the openings slightly in the ends of the tubes to increase the discharge area.
The holes along the length of the dis tubes vary in diameter, number & position. Left side is different to rt side. And they varied with carb model/engine & the engine the carb was used on. Nobody has been able to tell me how these really function, & how the size/position was determined. What this does tell you though is that when something is changed on the engine, this calibration will no longer be correct. That is why I solder those holes shut because they may adversely affect A/F delivery on a modified engine.
 
Geoff 2 said:
GS, referencing post #11. The pic showing the sec jets. Did you enlarge the openings slightly?

I would solder shut the holes along the secondary discharge tubes & angle the openings slightly in the ends of the tubes to increase the discharge area.
The holes along the length of the dis tubes vary in diameter, number & position. Left side is different to rt side. And they varied with carb model/engine & the engine the carb was used on. Nobody has been able to tell me how these really function, & how the size/position was determined. What this does tell you though is that when something is changed on the engine, this calibration will no longer be correct. That is why I solder those holes shut because they may adversely affect A/F delivery on a modified engine.
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No, I believe I left those alone. I did make some .156"s from .149 but they are not used.

As part of the buildup to dyno testing, I did some bench testing. I made a box to attach the carb to my leaf blower. I instrumented the carb to measure secondary vacuum draw, airflow, differential pressure, etc. One test I did was to measure vac draw vs air door opening as in the pic below. In pic #11 you will notice some soldered up holes but there are others you can't see. Another test I did was to measure draw with various holes added or covered up. What I found was that the holes near where the tubes attach to the top are for balance, left and right. Also found was that any hole outside of the "happy zone" of low pressure formed by the venturi effect between the baffle and air door reduced vac draw. So any hole I added was left alone if it were inside the low pressure zone. I have seen the angle cut like the CS series. One thing to remember is that on the CS, the angle of the tubes are different and the angle cut lands inside the zone. You will notice in #11 the straight line drawn on the tube. That is the boundary of the zone, u can't see the line on the bottom. I considered cutting at the lines to mimic the CS but decided instead to cut open the ends of the tube as in the Mopar tech paper. That way the fuel mix is not impinging as much on the back of the air door as I open it to max opening. The fwd edge of those holes are bent so as to contain the holes inside the zone.

I can see where the angle cuts will pick up hp in a situation where it is already too rich. It turns out that mine would have picked up from reduced fuel draw from such a mod as it was rich but I did not know that beforehand.

The 2 or 3 factory holes in the zone are at areas of higher vacuum. I put some right on the middle of the dimple and again it reduced the draw. Holes on the bottom of the tube or the front side also reduced draw.



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GS,
The TQ I tested last year on a 440 had all the holes in the dis tubes soldered shut, & the ends cut off at an angle, but the angle was less severe than on the CSTQ. Made 605 hp with 0.148" sec jets. Top end was a little rich, but decided to keep the 148s as the owner is going to instal cold air which will lean it out. I am aware of the difference in angles of the sec tubes between the CS & production TQs. My tech bulletins are pretty old. Only reference to hole size in the/tubes is in the SB section, says to makes them outsize, but no actual dimension is provided. Are there later bulletins?

I have a rare 1970 article on the TQ introduction. It shows a single TQ on a 426 Hemi with a cross ram intake that has a bolt on removable top that can take different carb combinations. Claims that HP increased by 30 when the sec baffle was
s removed.
 
That's a good result from only 440 ci..

The article I have is one that was sent to me so I don't know the date. But it mentions .101" and mine are bigger at like .143".

I also tried removing the baffle on the bench test. It reduced vacuum draw quite a bit with no increase in airflow. So I can see where the 426 would pick up hp if it were rich to begin with. I left mine in.

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GS,
Maybe I mistook your comments. I thought you drilled out the bullet ends of the d/tubes to 1/8". And which holes are drilled to 0.143"?

Something you may not be aware of. TQs were used here on 302/351 Ford engines. They were 9000 series, about 5 models. #9144 was one of them. It had 101 pri jets....098 sec jets. The air valve WOT opening [ spring tension ] , the sec t/blades opening, were the same as other TQs. The sec HSAB was 0.029". Go figure!

In the 1980s, I tried one on my 440/727 trans Dodge that I had. In 2nd gear, the car stopped accelerating as if a giant hand stopped it. Carb Had the 098 sec jets. Went home drilled the jets to 143 & that fixed it.
 
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