Leaking Carb

Omathisen · #1 (**permalink**) 07-09-2012, 12:10 PM

I have a Holley 3310-4 that has been leaking a little oil at the back when the car is cooling off. (Tightening things did not stop the leak.) It was coming from the gasked between the carb and the manifold. I bought a parts kit and replaced the gasket. (Just lifted the carb up to change the gasket.) Put the bolts back on and the airfilter and pumped the gas pedal which resulted in gas leaking out at the back on the right side.
Noticed there was one more gasket in the kit -- one with four big holes in it -- I added that, and the gas leak stopped. Then I am being told there should never be two gaskets - one on top of the other (although one sort fits inside the other actually).
I am obviously no mechanic but try to fix things if I can. Can anyone give me some guidance? Thanks.

patrickt · #2 (**permalink**) 07-09-2012, 12:56 PM

Quote:

Originally Posted by Omathisen

I am obviously no mechanic but try to fix things if I can. Can anyone give me some guidance? Thanks.

This is a typical Base Gasket for a Holley 4160 (a 3310-x). Is this the "gasket with the four holes" that you're talking about? Maybe you could go here: http://www.holley.com/HolleyCatalog/...pageNumber=100 and tell us what the other gasket looked like (or a part number). Sometimes rebuild kits have multiple gaskets.

Omathisen · #3 (**permalink**) 07-09-2012, 01:13 PM

Here you see the gaskets side by side and how one more or less fits "inside" the other. The open one (with no holes) did correspond exactly to the one that was on the car from the before.

patrickt · #4 (**permalink**) 07-09-2012, 02:24 PM

You don't use both at the same time and, generally, you choose the gasket to match the top of your intake manifold. Back in the old days we used to believe that the four holer was better at low to mid throttle and the open center was better on the top end, but that was probably just "youthful crap" and it was just the IM that made the difference. You're kind of making a "carb spacer" by using them both though. If nothing leaks, and you like the way the car runs, I'd leave it alone even with both of them on there.

EDIT -- Maybe a four holer on an open manifold will start to sag down and get sucked in after time. Surely someone on here has done that before and can give some first hand experience.

patrickt · #5 (**permalink**) 07-09-2012, 02:35 PM

jhv48 · #6 (**permalink**) 07-09-2012, 02:48 PM

Easy, one's blue!

FWB · #7 (**permalink**) 07-09-2012, 04:31 PM

Quote:

Originally Posted by jhv48

Easy, one's blue!

hehehe, good one...

Omathisen · #8 (**permalink**) 07-09-2012, 05:31 PM

Lightbulb time. Must have been the heat.

Gaz64 · #9 (**permalink**) 07-10-2012, 02:00 AM

Quote:

Originally Posted by Omathisen

I have a Holley 3310-4 that has been leaking a little oil at the back when the car is cooling off. (Tightening things did not stop the leak.) It was coming from the gasked between the carb and the manifold. I bought a parts kit and replaced the gasket. (Just lifted the carb up to change the gasket.) Put the bolts back on and the airfilter and pumped the gas pedal which resulted in gas leaking out at the back on the right side.
Noticed there was one more gasket in the kit -- one with four big holes in it -- I added that, and the gas leak stopped. Then I am being told there should never be two gaskets - one on top of the other (although one sort fits inside the other actually).
I am obviously no mechanic but try to fix things if I can. Can anyone give me some guidance? Thanks.

You have two gaskets fitted, that is not the way to fix a leak at the manifold.

Either run a gasket with compression limiting washers and/or fix your warped throttle body, like the pic patrickt posted above.

Or warp your throttle body further and break the baseplate mounting ears off.

You say it leaked out the back after you pumped the pedal.

Where would it be leaking from if your rear barrels are vacuum actuated, no accelerator pump?

Bitten Bob · #10 (**permalink**) 07-10-2012, 03:01 AM

I don't understand how fuel could leak from the manifold/base plate gasket ?

It should leak inside the manifold ou outside, but not from inside to outside ?

IMHO, you could face same problem I've got recently. I noticed a fuel leak which really seemed to come from the gasket between manifold and carb base plate (when following the leakage). I really wonder how it could be possible ????

In fact, I discovered that a fuel bowl screw had a stripped thread, and fuel was leaking from the screw head, running under the fuel bowl to the manifold and then going down along the manifold.
I put Helicoils in the 4 screw holes, and solved the problem.

But put a second gasket over the first one should not correct such a problem. And use manifold to carb gaskets is not the way you shoud fix a fuel leak IMHO again...

patrickt · #11 (**permalink**) 07-10-2012, 04:40 AM

If it's leaking oil from the back of the carb then it's probably the PCV hose going to the brake booster -- it just looks like it's coming from between the carb and manifold. Just put a little hose clamp on it and make sure the PCV valve is working properly.

Bitten Bob · #12 (**permalink**) 07-10-2012, 06:08 AM

Quote:

Originally Posted by Omathisen

I have a Holley 3310-4 that has been leaking a little oil at the back
the gas leak stopped.

I'm a bit confused about what is leaking

Is it oil (i.e. motor oil) or gas (i.e gasoline) ?

Remember that, when gasoline is slightly leaking and accumulating in very hot manifold curves, it evaporates, only leaving the non-volatil part of it as a residue, which also accumulates, giving some brown "oil", which absolutely looks like and seems to be motor oil, but is only "cooked" gasoline...