Question about TQ secondary operation

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Bewy

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I am a TQ fan, have used them since the 70s. Have a couple of Comp Series 850s & lots of production models. TQs were used on Aussie Ford 302 & 351 engines in the late 70s, all are 9000 series.
The question I have is about the sec discharge tubes, which are the same shape/size on the Ford carbs & Mopar TQs; bullet shaped tip with a small hole & various holes of different sizes along the length of the tubes. Size, position & number of holes can vary with carb model.
The question below I have asked on a few forums but have never got a credible answer.

[1] What is the significance of the hole position?
[2] Does the position mean that, as an example, the upper holes deliver fuel before the lower ones? Or the other way round?
[3] What determines the hole size?
[4] There is a large variation in sec jet size, with the same air bleed size, on Mopar carbs from 0.125 - 0.143". Blade opening & AV fully open is the same, so that does not explain it. Odd.
[5] The Aussie Ford TQs had a 0.029" sec high speed bleed, compared to 0.039-0.040" for Mopar carbs that I have measured. Some Ford TQs came with 098 sec jets, smaller than the 101 primaries!! Go figure. No wonder they got dumped for Holleys! The AV shape & WOT position & sec WOT blade position is the same on Ford & Mopar carbs, so that doesn't explain the very small jet size. The smaller HSAB might have some impact, but the area of of 143 is more than twice that of 098, so seems a big leap.
 
The air valve door opening on Thermoquads is certainly not the "same" as the opening tension and amount is completely adjustable.
 
The curve on the air door creates a lower pressure area around that feed tube and sucks the fuel through those holes. I imagine more holes would richen the secondary mixture?
 
I am a TQ fan, have used them since the 70s. Have a couple of Comp Series 850s & lots of production models. TQs were used on Aussie Ford 302 & 351 engines in the late 70s, all are 9000 series.
The question I have is about the sec discharge tubes, which are the same shape/size on the Ford carbs & Mopar TQs; bullet shaped tip with a small hole & various holes of different sizes along the length of the tubes. Size, position & number of holes can vary with carb model.
The question below I have asked on a few forums but have never got a credible answer.

[1] What is the significance of the hole position?
[2] Does the position mean that, as an example, the upper holes deliver fuel before the lower ones? Or the other way round?
[3] What determines the hole size?
[4] There is a large variation in sec jet size, with the same air bleed size, on Mopar carbs from 0.125 - 0.143". Blade opening & AV fully open is the same, so that does not explain it. Odd.
[5] The Aussie Ford TQs had a 0.029" sec high speed bleed, compared to 0.039-0.040" for Mopar carbs that I have measured. Some Ford TQs came with 098 sec jets, smaller than the 101 primaries!! Go figure. No wonder they got dumped for Holleys! The AV shape & WOT position & sec WOT blade position is the same on Ford & Mopar carbs, so that doesn't explain the very small jet size. The smaller HSAB might have some impact, but the area of of 143 is more than twice that of 098, so seems a big leap.
Hey Bewy! I'm not sure I can answer all the questions. But first I have to ask what "AV" stands for? Air Valve? And why are there lines through most of your text? My eye's are having trouble! Weird! Anyway, here we go...

[1] What is the significance of the hole position

A different hole position willallow the air and fuel with in the tube to mix longer or shorter as well as discharge in a different location, which may or may not have an effect on spreadingthe fuel in a better spot. Sorry, thats the best I can think off, so, the second half of the answer m ay have no merit.

And holy ****! I look up and now my text has a line through it! WTF? Hummmmmm

[2] Does the position mean that, as an example, the upper holes deliver fuel before the lower ones? Or the other way round?


I think the lower holes discharge the fuel first, but at the speed of which the fuel is pulled out of the tubes under vacuum, or actually due to theair velocity rushing past the tubes drawing it out, I don't think this is anarea to split hairs on tuning though it is an interesting idea to get a high speed cam to see what and where and when the fuel comes out of the discharge tubes. As to see what is exactly going on and when.

[3] What determines the hole size?

I think the carb and or engine engineers decided that one.


[4] There is a large variation in sec jet size, with the same air bleed size, on Mopar carbs from 0.125 - 0.143". Blade opening & AV fully open is the same, so that does not explain it. Odd.
Thats true. The jet size is determined by the tuners of the engine and what ever emmisions standard there under, or not.

[5] The Aussie Ford TQs had a 0.029" sec high speed bleed, compared to 0.039-0.040" for Mopar carbs that I have measured. Some Ford TQs came with 098 sec jets, smaller than the 101 primaries!! Go figure. No wonder they got dumped for Holleys! The AV shape & WOT position & sec WOT blade position is the same on Ford & Mopar carbs, so that doesn't explain the very small jet size. The smaller HSAB might have some impact, but the area of of 143 is more than twice that of 098, so seems a big leap.

The air bleed size is part of the tune. Americans of the time may have been under stricter levels than else where in the world. Also note that our trucks didn't need to pass the same test as the cars. So that is one thing. Also size of the engine, make, year, model of the car or truck can play a roll.

The jetting size difference mkaes sense because the primary needs to be bigger due to the rod dipping down into the primary jet to lean out the mixture. Under heavy acceleration, the lack of vacuum allows the rods to be pulled up en-ruchening the mixture. The secondary side is without any rods, so it just gets jetted accordingly. Nothing to figure! Just gotta know the carb and how it works and why.

Dumping the TQ for a Holley? What year? This may have been a surply issue since in america, there was no problems until the near end of the Carter Corp. when Chrysler started to use the
Rochester carb until fuel injection was standard.

 
At the risk of sounding like a jerk
who cares about which hole spews first, so long as the engine blasts off when I slam the pedal down
lol.
Have you ever seen a top view of an engine on the dyno, when the secondaries open? It's like total chaos.
I like the TQs also but probably for a different reason than you; I like the TQ-moan.
One time, I put one on a low-compression 318, with 2.73 gears and a manual-shift 904. And then I would nail it in too high a gear, and just wait and listen ...... here it comes.... ah music to my ears. Fifteen seconds to 75 mph. Stop, turn around, and lets go again,lol.
 
I am a TQ fan, have used them since the 70s. Have a couple of Comp Series 850s & lots of production models. TQs were used on Aussie Ford 302 & 351 engines in the late 70s, all are 9000 series.
The question I have is about the sec discharge tubes, which are the same shape/size on the Ford carbs & Mopar TQs; bullet shaped tip with a small hole & various holes of different sizes along the length of the tubes. Size, position & number of holes can vary with carb model.
The question below I have asked on a few forums but have never got a credible answer.

[1] What is the significance of the hole position?
[2] Does the position mean that, as an example, the upper holes deliver fuel before the lower ones? Or the other way round?
[3] What determines the hole size?
[4] There is a large variation in sec jet size, with the same air bleed size, on Mopar carbs from 0.125 - 0.143". Blade opening & AV fully open is the same, so that does not explain it. Odd.
[5] The Aussie Ford TQs had a 0.029" sec high speed bleed, compared to 0.039-0.040" for Mopar carbs that I have measured. Some Ford TQs came with 098 sec jets, smaller than the 101 primaries!! Go figure. No wonder they got dumped for Holleys! The AV shape & WOT position & sec WOT blade position is the same on Ford & Mopar carbs, so that doesn't explain the very small jet size. The smaller HSAB might have some impact, but the area of of 143 is more than twice that of 098, so seems a big leap.

This question has been asked before on other forums. The place for this discussion is here:Racing Fuel Systems • View forum - Carter & Offspring

This is a sub forum of a forum dedicated to carbs where interested parties are willing to discuss the technical aspects of Carburetion and engine tuning.
 
RustyRat,
I think you misread what I said. I am fully aware that AV opening is adjustable. What I said was that on the Aussie Ford TQs that had much smaller sec jets, the AV position [ at WOT ] & shape was the SAME as Mopar TQs, so how can they run on such small jets?

Rumblefish,
Sorry, cannot explain the lines. They do not show when creating the post, only show up after it gets posted. Yes, AV= air valve.
Holleys replacing TQs. That was done by individual Ford owners. These years were the final years of carbs in Australia & with tightening emissions, had really lean calibrations, so performance would have been lacking. So Holleys went on, when a set of numbered drills would have transformed the performance of the TQ......
The Ford TQs had larger pri jets, but also had larger pri air bleeds. Some had 101 pri jets, & these were 800, not 850 models. Not aware of any 800 Mopar TQs having pri jets that big. The met rods were generally 73/40, so leaner on the cruise step.

AJ,
Who cares? I care. As a tuner, if you know how something works, less likely to bugger it up if you want to modify or improve on it.
 
as a complete aside, if by accident, you leave out that thin, vertical flat plate in the secondary venturis, you'll know it immediately when you first engage the secondaries. The best description I can give, is that the airflow feels completely confused, hahaha.
 
Yeah, haven't tried that but have read it is a no-no.
Only time I have seen it removed was in an old magazine test when the Comp Series TQ first came out. They tested one on a 426 Hemi, cross ram intake with removable single 4bbl top. They claimed that removing the sec baffle added 30 hp...
 
let me say, emphatically, that was NOT my impression, at all. I found no advantage at all. If anything, it was a subtraction in power.
 
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