ANOTHER THERMOQUAD QUESTION

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CFD244

CFD244

"I LOST MY ID IN A FLOOD"
FABO Gold Member
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Hi Folks

Not sure if this is normal.............

I ran my TQ on a run stand and it performed great. When I removed it from the engine the following day, I noticed gasoline on both sides of the plenum floor of the intake (old school performer). I am not sure if it was there from running the previous day, or it leaked there?????

At any rate, I tore the carb down again and found no anomalies. I verified that the brass floats were dry, and confirmed the level was set at 1 inch with gasket on the top plate.

I filled the bowls with fuel and let it sit for 2 hours and checked the fuel well epoxy for dampness and found nothing.......And no drips on the work bench.

Do these things ever siphon through the main discharge nozzles or the accelerator pump circuit???

Am I chasing my tail, or is there something I am missing?

Thanks FABO
 
Often they leak down from the two small O rings.
Also there are small pieces on bottom side on Phenolic
that I epoxy on to prevent leaks. These are what I would
look at first if the carb runs fine.
I have not seen them siphon thru Accel pump or discharge
nozzles in my experience.
 
FOLLOW UP..............

After a couple of more hours sitting with fuel in the bowls, the venturi area of both primaries is damp, almost as if fuel is leaching though the phenolic plastic. I have 2 plastic body sections set up on my work bench, and it is happening to both. Still nothing from the underside though
GTX JOHN said:
Often they leak down from the two small O rings.
Also there are small pieces on bottom side on Phenolic
that I epoxy on to prevent leaks. These are what I would
look at first if the carb runs fine.
I have not seen them siphon thru Accel pump or discharge
nozzles in my experience.
Click to expand...
I have the middle section separated from the rest of the carb, and the o rings are out.
 
I have never seen Phenolic leak myself unless
they have been cracked or damaged in some way.
 
Spitballing. Thinking evaporation.
Maybe try a fluid less prone to evaporate, solvent/kerosene ?
In order for siphoning, bleeds would have to be plugged imho.
 
The top, black body & base need to be screwed together to compress the o rings. If the three sections are just sitting together, the fuel will rise in the black bowl to the level of the cut out into the pri bores & dribble into the bores.

I never, never use the factory o rings. And you should not re-use them. The design is too flimsy in my opinion.
Spend the time getting some standard section fuel resistant O rings, 3/8" OD, 1/16" thickness. A common size & should be readily available where O rings are sold.

Some more info: If the gasket between the bowl & base is not broken, then leaking caps over the pri main jets will NOT cause fuel to leak into cavity in the base plate & from there into the pri bores. Many people think is the cause of leaks. Only if this gasket is breached adjacent to the pri t/bores AND the jet cap epoxy has failed, can you get a leak into the pri bores.
What leaking caps cause [ gasket ok ] is a rich off idle condition/cruise until that excess fuel in the cavity in the carb base is used up.

Congrats on using the TQ.
 
inertia said:
The top, black body & base need to be screwed together to compress the o rings. If the three sections are just sitting together, the fuel will rise in the black bowl to the level of the cut out into the pri bores & dribble into the bores.

I never, never use the factory o rings. And you should not re-use them. The design is too flimsy in my opinion.
Spend the time getting some standard section fuel resistant O rings, 3/8" OD, 1/16" thickness. A common size & should be readily available where O rings are sold.

Some more info: If the gasket between the bowl & base is not broken, then leaking caps over the pri main jets will NOT cause fuel to leak into cavity in the base plate & from there into the pri bores. Many people think is the cause of leaks. Only if this gasket is breached adjacent to the pri t/bores AND the jet cap epoxy has failed, can you get a leak into the pri bores.
What leaking caps cause [ gasket ok ] is a rich off idle condition/cruise until that excess fuel in the cavity in the carb base is used up.

Congrats on using the TQ.
Click to expand...
I have an old National O ring kit with the correct size. How do I know if they are fuel resistant?

**EDIT** Don't mind the strange quote @inertia it was @Bewy 's quote. Still learning this damn computer :)
 
Bewy said:
A common size & should be readily available where O rings are sold.
Click to expand...
Geez, I made 10 phone calls and stopped 4 times while I was in town today.......Nothing!

Looks like those O rings need to be of the Viton variety. I found a supplier on line of Nitrile, but they are fuel resistant to AV gas, and not automotive...........I assume it has to do with the Ethenol in our fuel.
 
Metric is ok as long as they are fuel resistant. Metric equivalent is 10mm OD, 1.5 mm wall thickness.
Nitrile [ Buna-N ] is suitable with gasolene.
 
Mykin’s RN00170, Nitrile (BUNA-N) 70 durometer, is a general purpose copolymer of butadiene and acrylonitrile. This compound has a relatively high acrylo content, making it exceptionally resistant to petroleum base oils and hydrocarbon fuels over a temperature range of -40°F to +250°F
 
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