Cuda 340 Thermoquad unstable.

[Manuel]

Hi,

My Thermoquad was disassembled to instal a rebuilding kit by a Carb shop maybe some 9 months ago.  Car has been in shops for paint and repairs.

Was hoping it would now retain gas to start after a week or so but  no, still need to remove the filter cover to pour some gas in.

Carburator appears now to be rich, then too lean and the new mechanic has readjusted the float a dozen times with no luck. 

He installed another type of carburator and the engine works well with that one.

He is kind of lost on how to proceed with the thermoquad.

Any suggestions?

[Chryco Psycho]

Fuel is nothing like it was 50 years ago .
Heat will evaporate the fuel in the carb , blocking the heat crossover through the intake will help as well as heat reflector under the carb , Coolcarb has some options , even just sheet metal will help .
As for being unstable the phenolic body could be warped , causing vacuum leaks .

[71vert340]

I'm running a Holley on one of my Challengers with a stock 360 and the original Thermoquad on my 71 with the stock 340. The Thermoquad runs great on the 340 - I run 89 octane non-ethanol in it. The 360 with Holley runs great and again I run non-ethanol 89 octane. I'm put a stock Thermoquad on my 74 Charger with a 360 and running on non-ethanol, it runs great so far testing in my shop. I may add an octane booster to the gas if needed later.
Terry W.

[torredcuda]

Sounds like there is still an issue with the carb, was the body replaced with a new one when it was rebuilt?

[Bullitt-]

  There are a multitude of adjustments set out in the rebuild instructions that must be made in order.
The secondary air door seems to be where many go wrong and has a profound impact on performance...
This video shows how to adjust  https://www.youtube.com/watch?v=yI7XbmHQyeg

[Manuel]

Very interesting points to forward to the mechanic, thank you.

The carburetor body was not changed when they installed the rebuilding kit.

Were can I obtain the manual for him to follow the adjustments sequence correctly?

Very helpful video thx.

I will check at the gas station for the types of fuel they sell here in Guatemala.   I have been putting the most expensive one to all of my cars but from what I read here that may not be the best for the Cuda..

Thank you.

[Bullitt-]

 The rebuild kit should have included paperwork with specific settings for your model.
     Here is a manual goes into more detail
https://www.carburetor-parts.com/assets/manuals/carter-tq-manual.pdf

[Manuel]

Thx for the link Bullitt.

Q. Gents,

What would be a good place to send this Thermoquad for overhaul to the USA and any idea how much it could cost?

[Manuel]

Hi,

Sorry to be back here.

Problem persists.

We tried another carburetor for a month and engine worked well.  It was a different kind but a similar one that was adapted for the test.

Reinstalled the original thermoquad again with another new repair kit and it will sometimes have too much fuel in the bow and other times be very low in the bowl.
Putting the instruction manual level adjustment to the float provided too much fuel in the bowl when disassembled.

Technitian says that the plastic body is fitting well.

Questions,

1- I had the tank full of premium gas so, have not tried the suggested fuel,  can the type of fuel make the bowl be with high fuel level and sometimes opposite??

2- Can the suggested temperature issue in the heat crossover through the inlet cause the above mentioned fuel level variations??

Any suggestions?

We have almost lost all hope,  float level has been readjusted more than 20 tiemes.

As a last option I would need to send my Carb. to the USA for overhaul.    Any suggestions on where to send it to?

Thanks

[Bullitt-]

 I only know of two people to recommend for a proper rebuild.
1- http://www.harmsauto.com/services.html ... Member here well known, does great work by all accounts. https://forum.e-bodies.org/mlist/scottsmithharms_164
2- A gentleman from Canada, Ken Manley who obviously knows his Thermoquad.. I only know how to contact him through Facebook https://www.facebook.com/groups/254276841687055

  If the fuel is good type should be no issue unless it is high in alcohol content.
  They worked fine without the heat crossover blocked when new but blocking it is not a bad idea 
   Float level height should only be set to the specification, 1" I believe for most of this year. There may be other issues at play. I once found floats that had been adjusted incorrectly, tabs that pushed on the needle valves were out of shape but I was able to compare to a good set and corrected.

[Mr Cuda]

In order for anyone to make  suggestions,  it is critical to know what year thermoquad you  have.
71 carbs are  completely different than later ones, as the idle screws adjust the fuel, and later ones adjust air.
It sounds like your  carb is too lean

[Manuel]

Sorry, you are absolutely right Mr Cuda.   

It is a 1971 Cuda with its original TQ4972S

Can a lean carburetor make fuel level in it to vary as described?

[Mr Cuda]

A low float setting will constantly change the richness.  In your case going lean when float is at its lowest..
Careful taking the top cover off to not tear the gasket.

[Manuel]

Believe the problem will be solved.
Found one of the floats with some fuel inside.

[MoparLeo]

Sounds like the Carb shop that rebuilt it just put n parts and didn't test it. Where are you located ? You said you would send it to the US.