Leaking Holley Teapot

[RalphG]

I am finally opening up the Holley "teapot" carb on the 52 Merc to try and figure out why the gas leaks down into the engine while it sits for a few days. It pretty well drains the float bowl and I think the oil level in the pan is coming up which is cause for concern. Plus makes it hard starting and have to prime it. Where is the gas getting through?Everything looks ok to my untrained eye. Accelerator pump looks all there and functional. I have not removed the economizer diaphragm and stem yet.

[oldskool]

no expert but sounds like the power valve maybe leaking ,change oil

[Robz51]

Ralph, Are you guys in Canada using that crap ethanol fuel? Stuff we have in the US is 10% ethanol and has really played havoc on my cars. It evaporates quickly and causes fuel leaks on old fuel systems. I am going to use 100% gas as much as possible. There is a guy on the forum who specializes in teapot carbs. I've heard good things about his work.
Rob

[RalphG]

Originally Posted by Robz51

Ralph, Are you guys in Canada using that crap ethanol fuel? Stuff we have in the US is 10% ethanol and has really played havoc on my cars. It evaporates quickly and causes fuel leaks on old fuel systems. I am going to use 100% gas as much as possible. There is a guy on the forum who specializes in teapot carbs. I've heard good things about his work.
Rob

No, our gas is fine. I can leave an open container on the bench and it does not evaporate much at all. I think it is just old age on some of the parts in this carb. I should add that this car sat in the woods nearly 30 years before I resurrected it in 2014. The carb got a clean up and new top gasket at the time and otherwise it looked ok so we left it as is. I could live with the way it works but the gas leaking down is becoming a concern.
Are the power valve and economizer valve the same thing?

[mountstimothy0]

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[Robz51]

Yep, economizer and Powe valves are one in the same. I would bet it is your culprit since it is at the bottom of the bowl.
Rob

[RalphG]

Originally Posted by Robz51

Yep, economizer and Powe valves are one in the same. I would bet it is your culprit since it is at the bottom of the bowl.
Rob

Are you sure we are talking about the same carb? The name of this one is the Holley 1901 and that economizer diaphragm is at the top of the bowl. Mine is the 2 barrel carburetor. Maybe I am confusing the issue by using the wrong name but I thought I'd heard these type carbs with the float bowl up high called teapots?

http://www.oldcarmanualproject.com/m...901195223.html

[Robz51]

The diaphragm on the top uses vacuum change at full throttle to actuate or push the plunger of the the valve (with cross in the head) at the bottom of the bowl. That is the actual valve.
Rob

[rotorwrench]

If the PV gasket isn't right, it can leak around the threads of the valve. The jets can sometimes not seal if there is too much corrosion in the bowl. The float bowl can also leak where it is attached to the throttle body. If the float level gets too high it can leak from a lot of places but that's less likely if you've been running it.

[RalphG]

Originally Posted by Robz51

The diaphragm on the top uses vacuum change at full throttle to actuate or push the plunger of the the valve (with cross in the head) at the bottom of the bowl. That is the actual valve.
Rob

I had that one (at the bottom) out to inspect and clean. Saw nothing that indicated leakage. The only possibilities I can see are the accelerator pump jets or the main jets, the ones that go down through the choke plates. There are no other visible leaks and yet the float bowl drains whenever it sits a day or two.

[51 MERC-CT]

Why not set up the carb off the car in what would be it's normal position.
Fill the bowl to float level and let it sit to trace any leakage.

[scicala]

Robz51 has it correct. The ecomomizer diaphragm is attached to the top of the carburetor and pushes open the brass power valve in the bottom of the bowl when the manifold vacuum drops (engine load). Even if it were stuck open, fuel would not leak out of the carburetor. It just leads to the main wells for additional fuel when accelerating.
It's hard to say why the fuel disappears over a certain time, other than ethanol in the fuel and the engine being shut off pretty hot.

Sal

[RalphG]

Originally Posted by scicala

Robz51 has it correct. The ecomomizer diaphragm is attached to the top of the carburetor and pushes open the brass power valve in the bottom of the bowl when the manifold vacuum drops (engine load). Even if it were stuck open, fuel would not leak out of the carburetor. It just leads to the main wells for additional fuel when accelerating.
It's hard to say why the fuel disappears over a certain time, other than ethanol in the fuel and the engine being shut off pretty hot.

Sal

As far as I know we have less ethanol in our gas than you do in the U.S. This gas is leaking into the manifold and down past the rings is my guess as the oil level increases. I'll try filling the float bowl on the bench tonight and see if I can spot the leaks. Even if it is leaking out those main jets, how do I stop it? I've got a new carb repair kit here I'm going to install.

[rotorwrench]

I would check the fit of the float bowl to the base very carefully. They can get warped if tightened too tightly. All the fuel goes through that area so it is the single most troublesome spot on the top float carbs. There might be stains there and their might not. A person can put the carb together just enough to seal it and then fill the bowl with fuel and watch it for a period of time to see where it's going. If the bowl stays full, the problem should be fixed.

[RalphG]

Yes, there are only 2 screws holding the float bowl down to the base.
I installed the new diaphragm and spring over the power valve, then watched it for over an hour last night. Sitting on the bench with gas in the bowl and no sign of leaks. If it still looks good this morning I'll consider it ok to re-install and test.

[supereal]

If the power valve isn't leaking, there is likely a warp in the carb body. Old carbs have usually been apart many times over the years, and some of the screws were overtightened in an effort to prevent internal leakage. Before reassembly, we check for warping by placing a sheet of fine grained abrasive on a piece of glass, then rub the gasket surface on it. Any problems will how up as bright spots, often at the screw holes. Gasoline has a low surface tension and will leak at any voids in the body or gaskets.

[RalphG]

Originally Posted by supereal

If the power valve isn't leaking, there is likely a warp in the carb body. Old carbs have usually been apart many times.

Yes, the carb has been apart more than a few times. I let it sit on the bench overnight with gas in the bowl and there were no sign of leaks this morning.
So I have re-assembled and installed but did not get a chance to do a test run today. Hopefully tomorrow.

[scicala]

Originally Posted by supereal

If the power valve isn't leaking, there is likely a warp in the carb body. Old carbs have usually been apart many times over the years, and some of the screws were overtightened in an effort to prevent internal leakage. Before reassembly, we check for warping by placing a sheet of fine grained abrasive on a piece of glass, then rub the gasket surface on it. Any problems will how up as bright spots, often at the screw holes. Gasoline has a low surface tension and will leak at any voids in the body or gaskets.

As stated earlier, on this carb design, the power valve can leak it's butt off 24/7 and not contribute to fuel running down the manifold. In fact when the engine is off, the economizer diaphragm forces the power valve wide open.

Sal

[RalphG]

Finally got a few minutes to try a test start this afternoon. Same old thing, had to prime it several times and it only ran til it burned up the gas I'd poured in the bowl and stopped. That is different. Almost seems now the fuel pump is not pumping gas. It used to always run fine after priming. I guess I need to check that now but ran out of time.