I need education on the Thermoquad "staged accelerator pump" , that gives an additional shot when the secondaries open

[Brooks James]

found this in David Emanuels Carter Carburetors

the accelerator pump arm in the pic , you cant tell if the slot that is oblong as the pump linkage arm is in place is in place
in the pic the bottom hole looks like a circle, and you can see from the pic of the one I am familiar with, that it is slightly oblonged

or is it an optical illusion and they are both the same

if they are both the same, what am I not seeing that would provide an extra shot

OR

Is there different arm ?

is he using a wordy explanation to explain something that has been already happening that I am unaware of ?


pics comimg

 

[rumblefish360]

The pump shot plunger is spring loaded and moves a certain amount for the initial pump shot for the primaries. Then there is a time when the throttle arm continues to move without the pump shot linkage engaging the pump shot lever connected to moving the plunger. Depressing the throttle more moves the linkage up into the taller slot. The linkage is shoved to the top pushing the arm upwards some more for a second pump shot.

 

[rumblefish360]

Picture 1 - top. Throttle position at rest/idle/very light throttle.
Picture 2 - middle. Throttle @ 15/30%-ish open.
Picture 3 - bottom. Throttle is mostly too fully open.

This is the progression of the link from the bottom of the throttle arm connecting the pump shots lever positions on a 1973-340, manual transmission TQ carb.

Welcome to my garage…..

 

[Brooks James]

Picture 1 - top. Throttle position at rest/idle/very light throttle.
Picture 2 - middle. Throttle @ 15/30%-ish open.
Picture 3 - bottom. Throttle is mostly too fully open.

This is the progression of the link from the bottom of the throttle arm connecting the pump shots lever positions on a 1973-340, manual transmission TQ carb.

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View attachment 1716148702

Welcome to my garage…..

would that make it a double pumper lol

 

[Bewy]

Yes, sort of......

Not sure which model # was the cut in, but at some point a small portion of the remaining pump shot was saved for the opening of the secondaries.
Having used these carbs for 45 yrs, I have never had the need to use the inner hole on the acc pump arm. The triple pri boosters provide a very strong signal & a heap of pump shot is generally not needed.
Yes, these fabulous carbs continue to amaze us.......

 

[RLF Cuda]

Just went through 3 rubber accelerator pumps that didn't work at all. Had a leather pump and it worked first time perfectly. Not sure why the rubber ones failed. I would have thought that they might work for a while until the ethanol (ugh) in the fuel caused them to swell, but they didn't work from the start. Going to purchase a few more leather accelerator pumps, despite their current cost just as backup.

 

[lemondana]

Just went through 3 rubber accelerator pumps that didn't work at all. Had a leather pump and it worked first time perfectly. Not sure why the rubber ones failed. I would have thought that they might work for a while until the ethanol (ugh) in the fuel caused them to swell, but they didn't work from the start. Going to purchase a few more leather accelerator pumps, despite their current cost just as backup.

You always need to look at the acc. pump bore. Many times they are scored or corroded. Leather might be more forgiving. If your TQ looks like the ones that UTG has gotten off the Titanic and says they are all junk, you might need another top.

 

[rumblefish360]

Just went through 3 rubber accelerator pumps that didn't work at all. Had a leather pump and it worked first time perfectly. Not sure why the rubber ones failed. I would have thought that they might work for a while until the ethanol (ugh) in the fuel caused them to swell, but they didn't work from the start. Going to purchase a few more leather accelerator pumps, despite their current cost just as backup.

Where did you obtain the leather plunger?

 

[Bewy]

Leather plungers are available on the net & that is all I use. I have had many rubber ones fail; not sure why. Suspect softer rubber for E fuel....

 

[RustyRatRod]

Just put a double pumper on it. Much better carburetor.

 

[RLF Cuda]

Lemondana,
The TQ was in the best shape I have seen for a use carb in a very long time. I got it from a junk yard in the early 1980's and saved it all these years. The accelerator pump plunger bore was pristine. I tried 3 different rubbler accelerator pumps before finding this leather one. Unfortunately, I got the leather pump so many years ago that I don't remember when and where it came from. But now, with a good pump shot, the engine fires up cold instantly and idles at 1200 smoothly until the choke kicks off. This is what it should do and why I wanted to use the TQ. Surprisingly, even without a good accelerator pump, the car ran just fine with no stumble. The venturi flow must be sufficient to no need much of a pump shot.

I did have to change the throttle plate to one that had a vacuum advance port as this carb (9077S) was from a 77 440 HP with lean burn and didn't have a vacuum advance port. I don't think it is possible to drill the base for a port as there is a machined slot just above the primary throttle blade that controls the vacuum advance signal. But it worked fine with the base from an older TQ (but not as pretty as this one).

 

[lemondana]

That Vannith TQ guide that used to be over on Moparchat gave detailed instructions how to drill your baseplate out and add the vacuum nipple. I did a 9077 years ago, worked good. I got to the point years ago when I was buying TQ's, that I wouldn't buy one unless it had the vacuum nipple. There were plenty of the early ones around.

 

[Bewy]

Pretty sure all the 9XXX TQs had a ported vac adv port. Because the VA was switched to manifold vacuum via temp switch if the engine got too hot. The EGR port looks similar to the VA port, but not quite the same position. VA port is on drivers side, EGR on pass side.

 

[RLF Cuda]

For sure my 9077S base has no vacuum advance port. But the upper part of the carb was by far the best I have, so I swapped bases with another carb and all was well. I just started driving my restored '68 FB FS 340 and got 16.67 MPH the first tank. This was not ideal driving as I was in traffic and working on the carb a lot. So hopefully the next tank will be a more accurate representation of the fuel economy. But i must say, so far, the TQ is a wonderful carb. Just 1 quarter stab of the throttle and the engine starts right up from cold and idles at 1200 smoothly. Can't ask for more than that.

 

[RLF Cuda]

Found the text for adding a vacuum advance port to a TQ without one (ELB and ESA versions)
Adding vacuum advance port to ELB and ESA TQs:

Many Lean Burn carburetors lack a vacuum advance port because advance was controlled by the ELB computer. The port may be added to provide a vacuum advance signal for a conventional non-ELB/ESA distributor system. The vacuum advance port is somewhat tricky and is best performed by comparison to an earlier throttle base that has the factory port. Using ~5/32" drill bit, drill the throttle base where the vacuum port existed on previous units....drill into the open (roughly square) opening between the outside and the throttle bore. This will accommodate the vacuum fitting. Then, using ~1/16" drill bit, drill two holes just above the throttle plate into the same square opening from the throttle bore side one hole adjacent to the other parallel to the throttle plate. Then, using a knife or small screwdriver, blend the holes together into a slot. This serves as the off-idle transfer slot to feed the vacuum port. Press a short length of 5/32" pipe or an old fitting into the outside hole. Vacuum advance is now available. Using another base with the port as a guide will ensure proper placement of the transfer slot. Misplacing the vacuum idle transfer slot can cause an off-idle stumble and will necessitate additional tuning or replacement.
Credit: A Carto TQ Guide by Gary Lewallen
https://carbkitsource.com/tech/Carter/pages/tqguide-Vaanth.html