Time to give up on the Thermoquad?

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DionR

DionR

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Been fighting to keep the original Thermoquad on my Duster for some time now, but just about to give up. Ran fine when I first got it running again, only a slight surge/miss at light throttle cruise which I figured was too much initial timing. Well, the surge/miss is getting much worse and so I pulled the carb apart to see if I could see something wrong.

Only thing I can see is there is gas in the upper well on the passenger side (next to the choke, where the metering rod drops in), and it looks like the sealer I put on the main jet wells is getting gas on it as it just pealed of and felt like soft rubber (used the same stuff Demon Sizzler used). Tested the wells with some brake cleaner and they do seem to be seeping. Can't see why the wells filling with gas would make it feel lean, so I don't think that is the issue.

Can't see anything obvious, thinking about putting the Carter Comp Plus I have on the car. Really don't want to do that, I like how it's run before, but I can't see the problem.

Just as background info, this is on my Duster, low comp 360 with MP R/T heads, '00 Ram 5.9 roller cam and M-1 dual plane with an adapter for the Thermoquad. Tried plug wires/coil/ecu, but that didn't change a thing.

Any thoughts on what might be wrong before I give up?
 
What was the sealer used for?
If the sealer is getting gooey, some of it could be getting draged into the metering system. When the car is off, the heat stays behind and may be hardening, creating an obstruction.

For the price of gaskets (AKA Rebuild kit) it would be worth taking a bit of time to clean it up and out well.

Your light throttle surge/miss is the fuel curve outta wack. That condition is "Lean"
 
I agree with RF, rebuild it. NAPA can get a kit for you, I would suggest replacing the floats as well (sold separately). Check the bottom of the wells, the little plastic piece, you might want to pull them off and re-glue them in place using some good epoxy. There are small O rings in the bottom of the wells, are they there?

I took an old TQ and rebuilt it and it runs great on my car.

If you do rebuild it, pull the wells and put them back on with some good epoxy and let it sit for 2 or 3 days to fully cure before you put it back together.
 
I had the same exact problem with my lil red express. After pulling the carb apart I discovered the pheonlic ( plastic) fuel bowl had warpped. I replaced the fuel bowl ant it runs great ever sense. This is a notorious problem with T/Q s as they get older. I used to run into this a lot in the dealership back years ago.
 
Sealer was used around the main jet wells on the bottom of the fuel bowls to make sure they didn't leak. Used a page out of Demon Sizzler's mods and found the same stuff. Didn't hold up. Wouldn't have been sucked into anything to cause an obstruction, though.

Carb has been rebuilt already. Doesn't mean something didn't get missed, but it's not like I've been running it for 20 years and now I'm having problems with it.
 
Badsport said:
I agree with RF, rebuild it. NAPA can get a kit for you, I would suggest replacing the floats as well (sold separately). Check the bottom of the wells, the little plastic piece, you might want to pull them off and re-glue them in place using some good epoxy. There are small O rings in the bottom of the wells, are they there?

I took an old TQ and rebuilt it and it runs great on my car.

If you do rebuild it, pull the wells and put them back on with some good epoxy and let it sit for 2 or 3 days to fully cure before you put it back together.
Click to expand...

What epoxy would you suggest? The stuff I used to make sure the wells didn't leak didn't hold up, and all I did was smear it around the outsides of the wells. Pulling them off and gluing them back on with the same stuff would be asking for trouble.

And again, this was the same stuff that Demon Sizzler used. Don't remember the name of it, but found a post where he recommended it, tracked it down and put it on. All the wells did was seep and the stuff came apart.
 
fanofpetty said:
I had the same exact problem with my lil red express. After pulling the carb apart I discovered the pheonlic ( plastic) fuel bowl had warpped. I replaced the fuel bowl ant it runs great ever sense. This is a notorious problem with T/Q s as they get older. I used to run into this a lot in the dealership back years ago.
Click to expand...

Too bad you can't just go out and buy a new bowl. Thus my discouragement and thoughts of replacing the whole carb.
 
I had the same type of issue on my old ramcharger with a 360. Had a thermoquad and a MP dual plane intake. Tried changing the carb with no luck. Turned out to be a vacuum leak from a warped intake manifold.
~Michael
 
DionR said:
Too bad you can't just go out and buy a new bowl. Thus my discouragement and thoughts of replacing the whole carb.
Click to expand...

While a new bowl maybe super hard to find, taking your centesection and having the surface milled much in the same way a cylinder head is done would fix the top half.

The bottom half has an issue even with the well s removed. There are grooves on the bottom.

Has anybody ever used JB weld in the fuel bowl?
I used it on the front to fix a crack. The JB is on both sides of the bowl. No issues.
 
I'd think something like jb weld would hold up. I've used it before on the wells in a tq,and it was fine.
 
I've heard jb weld does not hold up to the junk they sell now. I think that's why the goop I used failed. Worked fine when it was just gas, but now with the alcohol in it, it doesn't hold.

At the same time, I fixed the crack in the front of the bowl with jb weld before I found the other stuff. It seemed fine. But that is really more of a dry area anyway.

I did fix the gas tank in the Dart with it a year or so ago, but I haven't put enough gas in it to know if it is still holding.
 
I also have some Mopar ATF RTV stuff that is supposed to be pretty good. Works well in most cases, maybe I should try it. Don't know if it's gas resistant, though. Probably not.
 
Any idea why there would be fuel in the metering rod/air bleed well on top of the upper casting? Seems like it might be related.

One thing I did not try before breaking the carb down was testing for vacuum leaks. Meant to, but forgot.
 
Well I guess you could throw a wanted ad on here, maybe someone has one laying around.
 
"M-1 dual plane with an adapter for the Thermoquad"
...the adapter in-between could be giving you a problem too.

What is the TQ number on the baseplate?
 
I've used that on gas tanks with holes and tears,and it worked!
 
I have a couple TQ's that are good for parts. PM me if intersted.
 
Badsport said:
Well I guess you could throw a wanted ad on here, maybe someone has one laying around.
Click to expand...

I've got 6 or 8 Thermoquads, and at least one spare bowl that would work. The wells on it were seeping, too.

That's the problem, just seems like I am fighting an up hill battle with parts that are wearing out and can't (easily) be replaced.
 
mrbill00 said:
"M-1 dual plane with an adapter for the Thermoquad"
...the adapter in-between could be giving you a problem too.

What is the TQ number on the baseplate?
Click to expand...

I'm not the first to run an adapter, and it ran fine earlier and has just developed the problem.

Also, I cleaned up the intake to match the adapter, so I don't have any sharp edges to create airflow problems.

Number is a 6454 (if my memory is correct).
 
Not sure the leaking wells is the complete problem, though.
 
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