Looking for thermoquad assistance

[rottenfish]

I am trying to put a few miles on my mildly built 360/4spd, but I am having trouble with the carb. I am running a TQ. I have two of them, both them are exhibiting some drivability problems. The one that has me stumped is this:
It starts and idles fine, but when you try and accelerate lightly or cruise, it "seems" like it is running out of fuel. It wants to die, and the engine decelerates while you are trying to cruise. If you push it a little harder, as soon as the secondaries start to open, it takes right off. It seems that something in the primary metering is out. The fact that it has plenty of fuel in the secondaries leads me to believe the floats and float valves are good and set correctly. I have had this carb apart a few times, but I can't find the problem. Is this an issue with the metering rods or the jets in the floor of the carb? The primary nozzle wells?

The other TQ surges, and won't idle at all. Any input on either problems would be hugely appreciated. Thanks.

[fishn4cuda]

I love my TQs. They are famous for having a dead spot in them. It's been a long time since I tinkered with the adjustments. I do know there is an adjustment on the side that help eliminate the dead spot. Chryco will probably know.

[Bullitt-]

The float level has more to do with the idle transition circuit than you may think, other than needing cleaning out that may be where the problem is...
Local guy has a cammed 440 & says the metering rod spring was difficult to get right because the vacuum being low he needed a lighter spring.
 check this carb basics article, its about Holly's but the basic concepts are the same.
http://www.chevyhiperformance.com/techarticles/83118_carburetor_basics/
good T/Q Specific article
http://australianfordhardtopclub.org/Carter_Thermoquad_info.htm

[Challenger6pak]

It sounds as if your secondary air door is opening too soon causing a lean condition. It needs more tension.

[rottenfish]

Thanks guys, great info. The TQ article on the Australian site was A1. I think my problem is in the metering rod adjustment. It seems that the issue is happening before I am engaging the secondaries. I haven't tried anything since my original post, but I have a few things to check now. I am going to lock out the secondaries just to confirm that the problem is in the primaries, then raise the rods a hair to richen the mix. I will post my results...

[MEK-Dangerfield]

Swapping to a Holley will change things.    



  Mike

[73HEMIRALLYEGUY]

The problem you are having isn't going to be fixed with the metering rods. I have over 22 years experience with Thermo-quads on mopars. The problem will be solved by drilling out the small brass emulsion tubes. These tubes areinside of the aluminum tubes that sit against the o-rings in the bottom of the main well of the plastic bowl. Be careful here. You will need a carburetor drill set. Mac tool or snap-on dealer. Carefully gauge the current emulsion tube size using you drill set. Once you have determined the size. Open the tube diameter by .008 or as close to that as possible on both sides. assemble carb and test drive. You may need to repeat this proceedure more than once . until the flat spot or lag is gone. Good luck.

[ntstlgl1970]

I would also scrounge the wrecking yards for parts (jets/metering rods etc.) for some tuning options in case you get to a point where you want to start drilling the jets too...

Since most guys don't mess with them you can usually get spares cheap or free. Might want to practice on a junker carb before drilling on your good one

[73HEMIRALLYEGUY]

Very good point.

[ntstlgl1970]

Although not specific to what you are doing, here is a good article with some more insight into how to modify the t-quad even though they are working with E-85...it's an interesting read.

http://www.moparts.org/moparts/picture/print/pages/Vraa.html

[73HEMIRALLYEGUY]

Good article. Information is where it's at. Like No.5 said MORE INPUT!

[rottenfish]

I have done some tinkering... I found the "tree" that the rods ride on was loose in the center, and was hanging up on one side. I replaced the tree, which now moves freely and stays level. Tomorrow is test drive day to see where we are at.

I am curious about these emulsion tubes... what would cause them to have to be drilled out? Is this a modification, or a cleaning procedure? The engine is warmed over, but I can't imagine it is enough to render the TQ this helpless. Engine is 360 +.60, ~10.5:1, 276*/474 cam, 340 exhaust manifolds, weiand dual plane intake, HV mechanical fuel pump, 4spd trans.

Thanks all, I am learning more than I ever wanted to about these TQ's. I have always liked them, but never really had to troubleshoot them before. I have been fortunate enough to just be able to rebuild them and have them work great; up until now.

[ntstlgl1970]

It's a modification, from the factory, the carb is calibrated for the stock engine and low(er) emissions. Once you change the combination outside of the factory "window" then modifications are in order. If the metering rod hangar was sticking, that will make a huge difference by itself. Guys I know that have done the emulsion tube modifications have been very happy with them, even with a stock engine. Just take small steps.