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6 barrel carburetor

racinguy25

racinguy25

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I am having trouble with the center carb on my 70 Superbird 6 barrel. These is a small valve on the top of it that has a piece of linkage that pushes it down. 'Sometimes' it leaks gas, it just bubbles out of it. I just discovered this and am lucky I haven't had a fire yet. This valve (sorry I don't know the name of it) has an outlet about 2 inches over, that on my car has a black plasitc cap on it. The cap was there when I bought the car, but I suspect the leak is caused by the lack of a place for the fuel to go. Question, should there be a hose on this outlet and if so where does it run to? I am pointing a screwdriver at the valve and you can see the capped outlet,3/8" hose,
Center carb.jpg
a couple of inches past the valve.
 
That's called the Homogutator valve. I don't know much about it, but I do know that you have to be extremely careful with that!
 
That's a bowl vent valve. And the bowl vent tube on the side should NOT be plugged, it should be connected to the evaporative emissions system. Consult your service manual for the proper diagram.
 
That is a 1971 style carb. The bowl vent hose would go to a nipple on the breather on the valve cover.
 
If fuel is coming out of the bowl vent the float level is too high, You have a bad needle and seat or a bad float. It is supposed to vent air and vapor and not fuel.
Oh and I moved this thread to the fuel and air systems forum
 
And if you're shooting for originality, on a 1970 6 pak the center carb has a slightly different design as Jim C. has already mentioned above. Pic is from my November of 69 built 1970 Cuda.

IMG_0864.JPG
 
The enclosed idle bowl vent valves are correct for 1970, but only on California spec production. If not running an evaporative recovery system, capping it off defeats its primary function. As mentioned, if fuel is leaking at the valve, there is a needle & seat or a float-float level issue.
 
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What is the number for the correct 1970 carburetor? Would Classic or ?? have the correct one. At the least I will rebuild this one and know how to vent it with a different breather on the valve cover. Thanks for all the help, especially the valve name, homo something.
 
’70 Federal production center carb is R-4375A manual trans, R-4376A auto trans. California or E.C.S cars used R-4374A manual trans, R-4144A. From the looks of the bowl screws, it would appear you may have a later Holley reissue of the ’71 center carb (R-4670A). At some point early on, replacement center carbs, even from the dealer, all came with the later enclosed idle bowl vent bowl and nipple by my experience. If not running a vapor recovery system, should be left open to the atmosphere. Again, shouldn’t be fuel leaking out of the vent valve with normal fuel level in the bowl.
BTW, pretty easy to change out the needle and seat, no need to pull the carb or bowl for that, I’d start there.
 
Mine is an October 69 build has a regular fuel bowl without any kind of vent, can't say it's original I bought it 1979 who knows.

IMG_2821.JPG
 
I would wager that bowl has been replaced with a non-OE bowl. Should have had idle bowl vent valve originally, open or enclosed. No OE Holley center hung primary bowls without idle vent valves. Could be had from Holley for an aftermarket model.
 
72RoadrunnerGTX said:
’70 Federal production center carb is R-4375A manual trans, R-4376A auto trans. California or E.C.S cars used R-4374A manual trans, R-4144A. From the looks of the bowl screws, it would appear you may have a later Holley reissue of the ’71 center carb (R-4670A). At some point early on, replacement center carbs, even from the dealer, all came with the later enclosed idle bowl vent bowl and nipple by my experience. If not running a vapor recovery system, should be left open to the atmosphere. Again, shouldn’t be fuel leaking out of the vent valve with normal fuel level in the bowl.
BTW, pretty easy to change out the needle and seat, no need to pull the carb or bowl for that, I’d start there.
Click to expand...
I'm going to take your advice and change out the needle and seat, check the float and etc. And, figure out how to vent it, probably to the valve cover breather although I don't like the look of that too much since it is not stock. That will probably solve my problems, thanks.
 
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racinguy25 said:
I am having trouble with the center carb on my 70 Superbird 6 barrel. These is a small valve on the top of it that has a piece of linkage that pushes it down. 'Sometimes' it leaks gas, it just bubbles out of it. I just discovered this and am lucky I haven't had a fire yet. This valve (sorry I don't know the name of it) has an outlet about 2 inches over, that on my car has a black plasitc cap on it. The cap was there when I bought the car, but I suspect the leak is caused by the lack of a place for the fuel to go. Question, should there be a hose on this outlet and if so where does it run to? I am pointing a screwdriver at the valve and you can see the capped outlet,3/8" hose,View attachment 1096782 a couple of inches past the valve.
Click to expand...

I totally agree with others....it is a carb fuel bowl vent valve. Looking at your pix, the carb appears to be a Holley 4140 series, as an after market/replacement for the origional Mopar Holley 4375. The bowl screws are hex head vs round head slotted type. Since your car is a '70 model, it would have had an open fuel bowl vent. Later years, 1971, would have had a closed bowl vent with a hose connecting yhe vent valve to the valve cover breather connection. Unless your car was an origional California vehicle, then it would have had a closed fuel bowl vent as part of the CAP/CAS emission control package.
Failure to vent the carb, usually results in fuel percolating (boiling) and extremely hard starting after a hot soak, due to fuel dribbling down the booster venturi. Moral of the story.....vent the fuel bowl.....either externally (open) or thru the valve cover breather. The condition is aggravated by today's ethanol blended gasoline because of the low vapor pressure, which allows a lower boiling point of the gas. Just my opinion of course.
BOB RENTON
 
RJRENTON said:
Failure to vent the carb, usually results in fuel percolating (boiling) and extremely hard starting after a hot soak, due to fuel dribbling down the booster venturi. Moral of the story.....vent the fuel bowl.....either externally (open) or thru the valve cover breather. The condition is aggravated by today's ethanol blended gasoline because of the low vapor pressure, which allows a lower boiling point of the gas. Just my opinion of course.
BOB RENTON
Click to expand...

This has been a very interesting thread for me because I've learned something that I didn't know before. Much thanks to the OP [racingguy25] for starting this off by posting his problem and to the membership here for responding with helpful suggestions, information and photos. I've had my center vent screw in my carb since I've owned the car [20+] years, and while it runs pretty good that way I have also experienced the hard starting that Bob Renton described when the motor is hot, though in my case I wouldn't say it's 'extreme'. I'm going to remove that vent screw now and let her breathe a little bit.... :thumbsup:
 
440+6 said:
Mine is an October 69 build has a regular fuel bowl without any kind of vent, can't say it's original I bought it 1979 who knows.

View attachment 1097344
Click to expand...

Lol, I bought my used '70 auto with shaker base plate setup in '78. The 3219 dated 4376 center had no bowlvent. One might wonder if it was common to just replace the bowl with a no vent due fuel leaking for whatever reason.
This picture is from '04. It's the same bowl from '78.......
upload_2021-4-17_14-8-10.png


I'd guess the 6106 center would never have had the bowl vent.....
upload_2021-4-17_15-1-58.png



racinguy25 said:
I am having trouble with the center carb on my 70 Superbird 6 barrel......
Click to expand...
Curious, What are your list numbers?

Replacement carbs can still be ordered it appears............
Holley 0-4670 350 CFM Factory Muscle Car Replacement Carburetor
Holley Chrysler OE Muscle Car Carb | JEGS
 
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