72 Thermoquad 6138s

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A 6138S is for a 72 340 with a manual transmission. Why would there be a problem with yours??
 
moparstuff said:
Some claims that the plastic part in the middle of the carburetor tends to be damaged and cause a leak
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They can warp. That's a decent carb for a street car with some moderate power upgrades or even bone stock.

Get a rebuild kit, do your homework and carefully rebuild it.

I will say this, it's a bit of a learning curve to get them just right, but once you do they are a great carb.
 
I run an 850 cfm thermoquad off a 73 440 on my hopped up 318 with a manual transmission behind it. I have had my best results with these carbs. If you can do better with a different carb on the street it won't be by much. There are four basic adjustments. Idle speed and mixture just like most carbs but you can also adjust the spring tension on the metering rods and secondary air valve door. TQ's have 3 step metering rods that are adjusted to the vacuum your car makes at highway cruising speed. The air valve door should be as loose as it can be without the motor bogging. Go loose and tighten in 1/2 turn steps and test drive til big is gone. Once it is set you will see how great a carb they really are.
 
moparstuff said:
Hello

I have this thermoquad 6138s. Are there any problems with this one?
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It should be a good carb to use if it is in good shape. It is really the first year TQ you want to avoid. It is metered differently. Also the race TQ's.
I'm not sure if new fuel bowls are available. (*I think they are*)

If you have a warped fuel bowl, it may be possible to sand down the top. A large flat area of sand paper on a table. Move the bowl around, not just back and forth.

The throttle shafts can be worn out. They can be bushed.

Mischief gave a good post. I like to start with 2-1/2 turns on the spring to start. It is a safe starting point. From where the secondary air door is completely loses and hanging, start to turning the screw to close the door. Once the door closes, (makes contact when it closes) start counting the turns of the screw there.

Again, it's a very safe spot to start tuning the primary side of the carb without a secondary bog to interrupt and confuse.

One pain in the a$$ is the choke. The OE design is an external choke well. If it is nice outside, removal of the choke plate would be very helpful for tuning and driving.

Another pain is filling the fuel bowl. Heat can make the fuel disappear. One way to help avoid this is the use of the OE "Thick" gasket. It is approximately 3/8 thick. This also helps protect the fuel bowl from cracking & warping.
 
Good point about the fuel disappearing Rob. I sealed the bottom of the fuel wells with epoxy and the carb is always dry when I go to start my car after it sits. Going to install an electric fuel pump soon.
 
the 6138 is a great carb. in stock elim, those 340's can run 10.80 @ 120 mph with this carb!!. as for warping, the bowl, if you have EGR system, it blows hot exhaust under carb , it goes right into intake. this will cause warpage. we run thin gasket, on a cast iron manifold, never had warpage. also, no exhaust EGR is used . on 73 manifolds, we block the EGR fittings in floor.
 
Mischief, I was thinking about a mention for an electric fuel pump but it is a drag to write about that turn off even though it is an excellent addition. I just tried out the Edelbrock electric fuel pump and so far, I like it a lot. Very quite. It Uses a relay. I remember some members saying it was to loud. I have to sooooooooo disagree with that. Also, I'm guessing these guys never ran a Holley fuel pump back in the 80's or 90's. LMMFAO!!!
(BRRRRRRRRRRRRRRRRRR)

perfacar
I have a '72 & '73 intake manifold. I like the '73 more only for the choke well not being directly in the heated path. Floor jet seal up and a die grinder to smooth work for me.
Still, the heat blocking of the head/intake port area is a fine move if cool or winter air is not an issue.
Best to block it at the head rather than the intake but both work.

It is amazing, that stock eliminator. 10.80 huh? WOW! Very quick for being very restricted. Makes you wonder what could be done with a lack of rules or none at all!
 
The main bodies do not warp on performance applications. This is total horse hockey. Where this myth got started was when the TQ was used in stock factory applications during the catalytic converter years. The extra under hood heat caused from the converter and all the other emission controls is what caused the plastic main bodies to overheat and warp.

All of this is avoided on performance builds, because there are no converters or emission controls and hot rodders don;t let their stuff run hot. If you come across a TQ whose main body id warped, it in all likelihood was warped to begin with from whatever it came off of.
 
I had one warp on me in a non stock application. Easy fix as described above.
This is not to throw crap at Bobby (RRR) What he wrote is true, it is the high heat that warps the bowls, hence my saying "Use the thick OE type gasket" as to help remove heat from the carb. Less heat on that item the better no matter the manufacturer of carb.
 
Thanks for help my car is finish With carburator.

20160508_121217 [150483].jpg


20160508_121234 [150482].jpg
 
Hey! That is nice! Good looking carb.
That second picture is the idle stop correct? When the car is turned off?
 
mine is leaking a little on the bottom and the car is not launching hard it just dies (4speed), don't know if the fuel leaking could cause this or its clogged on the low speed. o-rings are good and don't leak. cold starting without choke is painfull too even on hot days. I dont want to get rid of the TQ it gets good mpg and it is stronger than the avs i had before. someone had any problems on launching hard the car?
 
Did you try a high float level setting?
Address the other issues first.
 
Golden_commando said:
mine is leaking a little on the bottom and the car is not launching hard it just dies (4speed), don't know if the fuel leaking could cause this or its clogged on the low speed. o-rings are good and don't leak. cold starting without choke is painfull too even on hot days. I dont want to get rid of the TQ it gets good mpg and it is stronger than the avs i had before. someone had any problems on launching hard the car?
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Tighten up the spring on the secondary air valve till the bog goes away.
 
rumblefish360 said:
Did you try a high float level setting?
Address the other issues first.
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I didn't, I set them at 29/32 but I'll try set them higher to see if it gets better, maybe its the floats like you said the idle mixture needed to be 4 turns out to have a good idle
 
What engine are you running? TQ are always lean and need a choke and pull off to start easy, even in warm weather. Small Block carbs are leaner than Big Block carbs.
 
66fs said:
What engine are you running? TQ are always lean and need a choke and pull off to start easy, even in warm weather. Small Block carbs are leaner than Big Block carbs.
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Its a 318 .030 with a voodoo cam, 9-1 compression, eletronic ignition with chrome box, action plus intake, 6138s thermoquad(340 manual) with .098 jets(stock its .095) sparks are light brow, cruising and wot are good the big problem is the take off and cold start, I'm not running choke because the intake has no choke well like the original, its my daily driver
 
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