carb gasket leak

[Carnut]

I need some help. I have a 1966 with a poly 318. It came with a replacement carb on it, I think its one that covers a wide range of years as I believe I found it in a factory dodge 1978 trailblazer manual. Someone had drilled holes in the throttle plates so I could not get it to idle below 800 rpm. Looked on line and found one on ebay brand new, just like the one I took off. I also bought a thicker base gasket as the thin ones it came with (fel pro 60045) I have never had good luck getting them to seal. A host of issues (hose particles in the needle and seat, float stuck, accelerator check ball stuck, etc) have happened, most of which were my fault or just bad luck, and I have had it on and off many, many times. Between issues I have had to switch gaskets as if I use the gasket more than once it leaks. I even resorted to using the thin ones that came with it, which leaked before I got 10 miles on them. This last time I bought another new gasket, I have been using fel pro 60188, and it really didn't seem very flat (taco really) but I used it anyway. They are maybe 3/16 thick. I have to order them in so it takes a couple days each time. I tightened it with a cross pattern to make it as even as I could. The gasket is leaking (again) at the bottom of the carb and causes fuel to keep pouring into the engine after I shut it off. I put the carb on a 12" thick granite at work and the bottom is flat. Is there a better gasket to use than the 60188? The last new one didn't seem very flat, and it doesn't seem like a lot of meat on the sides. There are little cut outs on the sides which I don't know if they are really needed, minimizing the sealing area. I would estimate 3/16 coverage on the sides closest to the throttle plates with the thick gasket, 1/8 with a thin one. For some reason I thought I have reused base gaskets in the past, but for the most part the thick ones all seem to be one and done. The thin ones don't cut it at all. Do I just keep using the same gasket or does anyone have a recommendation for a better/different one? Am I missing something or is there a better way? I didn't check the intake but I can't imagine the mounting flange of a 2 barrel cast iron manifold is warped enough for this. I really believe this last time it was the gasket, but with all the issues I have encountered, I am starting to loose it. I am tired of buying $8 gaskets but at the same time I believe I have all of the other issues (knock on wood) resolved. Just wondering if someone has a better way to seal this thing before I buy yet another one....

 

[steve340]

If that gasket under the carb leaked you would most commonly get a vacuum leak.
If you are getting a fuel seep or leak it will probably be something else.
Fuel coming out after you switch the engine off can be a blocked air bleed.
Or a leaking float needle and seat.

 

[69Bee]

Sounds like a cheaply rebuilt carb. If fuel keeps flooding in the intake, from the booster nozzles I assume, the float is stuck or the float level is set too high, so fuel just keeps pouring in. As far as the gasket goes, it is fine. The notches uncover the transfer slot that surrounds the throttle bores on the bottom.

 

[Carnut]

If that gasket under the carb leaked you would most commonly get a vacuum leak.
If you are getting a fuel seep or leak it will probably be something else.
Fuel coming out after you switch the engine off can be a blocked air bleed.
Or a leaking float needle and seat.

It is definitely a vacuum leak when it happens. Idles rough. Carb spray changes RPM depending how bad it is. When I shut it off and you look down the carb, you can see gas dripping out of the venturi because of the vacuum leak. Eventually it seeps through between the carb and the gasket. I believe it is still sucking a vacuum because of the leak until the pressure equalizes. If I put a new gasket on it has fixed the problem, (until I came across all the other ones...) but each time I change it, its only good once. The gasket also has plastic inserts for the studs, so you can only tighten it down so much before it is just bottoming out on the plastic. I had the bright idea to cut the inserts lower to allow it to squish again but it didn't work. Just ordered another one but I wish there was a thick one that had more surface area, and unfortunately one I could reuse!

 

[steve340]

It does not sound like you have a vacuum leak. A smaller leak makes a sort of squealing/whistling sound.
A vacuum leak does not "equalise" or make fuel drip from the boosters.
Look a fixes/suggestions posted earlier - best guess from what you have posted the problem is in the carb itself.
If wet fuel is involved - vacuum is almost certainly not.

 

[Carnut]

You guys were right, float was stuck again. I believe I found the problem to be the spring that holds the float pivot in place was binding and causing the float to stick. Thanks for your advice, you were right on.

 

[threewood]

Glad you fixed it. As for gaskets, the thicker one you show pictured has come in a few BBD rebuild kits and is pretty good but once they crush they are hard to seal because the mount holes have metal inserts in them so you can only torque them so much.