Help please - NH Carb Leak from Bowl Drain Valve Assembly.

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Model T Ford Forum: Forum 2016: Help please - NH Carb Leak from Bowl Drain Valve Assembly.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Melham on Tuesday, September 20, 2016 - 12:50 pm:

This is doubtless a complete beginner's question but I would be extremely grateful for any advice.

I've got a newly rebuilt NH Carb, centre drain (1926-27), and I'm having trouble stopping a slow leak around the drain plug assembly. New bowl, new drain plug assembly, new gasket (installed on the outside, as required). The actual drain valve is fine, but I simply cannot seem to stop there being a slow seepage of gasoline from under/around the gasket that fits between the plug assembly itself and the bowl.

I tried tightening the plug, of course, but I am concerned that I will strip the brass threads. (I have done this before!) How tight does one have to make this fitting?

The new gasket is from Synder's and specifically for this carb, but is surprisingly hard-surfaced.

I really need to run my car this week, but am reluctant to fire it up with gasoline leaking around the bottom of the bowl. Is it normal to have a small seepage there - should I just run the car anyway, with a fire extinguisher to hand? Should I find some gasoline-proof gasket glue to use? Should I just haul on the nut and risk another stripped assembly?

Any advice would be very gratefully received. I'm in town with my car for only a few days, and very much need to get it running to run-in a recently result engine before packing it away for the winter.


Top of pagePrevious messageNext messageBottom of page Link to this message  By ALAN FAIRCLOUGH from Houston, TEXAS on Tuesday, September 20, 2016 - 12:52 pm:

I would resort to teflon tape.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Melham on Tuesday, September 20, 2016 - 12:57 pm:

Thanks! I didn't think of that. Not around the brass threads of the plug, but on top and below the gasket. Right?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Tuesday, September 20, 2016 - 01:02 pm:

Don't do that. It will splinter off in to a small piece inside that will work it's way into the main jet.

Just make a new gasket. Some of the kits I've seen have a very hard gasket that will not seal against the worn and probably previously rusted bottom of the bowl. You can buy a small piece of gasket paper and make one or you can go to the plumbing department of any good hardware store and they will have semi-hard gaskets. That is a 9/16 stud as I recall. Take the brass piece with you.

The vendors are aware of this as they are aware of the needles that are so rough they won't seal but won't lean on the supplier to do anything about it.

You might want to just buy a new bowl on your next order from Lang's and replace the one that the rebuilder didn't fix.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Longbranch,WA on Tuesday, September 20, 2016 - 01:03 pm:

Gasoline & Teflon tape are not compatible - it turns to mush. If a sealant is needed, use aviation EZ Lube - available at Lang's or any aviation supply store.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Tuesday, September 20, 2016 - 01:07 pm:

You can get a roll of thick gasket paper from a local parts store and cut your own softer gasket. It's a handy thing to have and will probably last for years. If that doesn't stop it, add Permatex.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, September 20, 2016 - 01:17 pm:

Stan,

He already has a new bowl.

Tom,

Check the bottom surface of the bowl for flatness and finish. Any grooves or roughness could allow seepage. Try this next. Rub each face of the gasket on a bar of soap. Enough to deposit some small thickness of soap on the gasket faces. Also, rub some soap onto the face of the drain valve flange and the bottom of the bowl, where the gasket touches it. Gasoline will not soften or dilute soap.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Harris, Huntington Beach California on Tuesday, September 20, 2016 - 01:33 pm:

I had this happen with a brand new repop NH. The needle valve on the bowl drain did not seal. It was a manufacturing defect. Very frustrating but resolved by swapping it out with another new one. Pretty much what Stan refers to in his third paragraph above.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Tuesday, September 20, 2016 - 02:30 pm:

Or, you can make one from lead, which is far easier than you might think. Steal a wheel weight from some junker -- a nice big one, pound it down to about 1/8 thick, (I actually squish it in my shop press) punch a hole in it, trim around the edge and put it on. A lead gasket will stop virtually every leak.

If you are feeling bad about stealing a wheel weight off the shop truck or the neighbor's car or one at the motel you can buy a wheel weight or other lead. I have it in sheets 12 x 12 inches from 1/32 to 3/16 by 32nds. It is just the handiest thing you have ever seen in the shop. McMaster Carr is your friend but you don't have time to order from there and you do have time to steal one. It will be dark in Calgary by about 7 PM, it's the equinox tomorrow or sometime soon.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary H. White - Sheridan, MI on Tuesday, September 20, 2016 - 04:50 pm:

A large fishing sinker can also be a source.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary H. White - Sheridan, MI on Tuesday, September 20, 2016 - 04:54 pm:

A large fishing sinker can also be a source.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Melham on Tuesday, September 20, 2016 - 06:28 pm:

Thanks to all for the imaginative suggestions. In the end, I brought the offending gasket to my nearest auto parts shop and sourced a rubber O-ring (gasoline proof) of exactly the right size. The bowl of my carb is now bone dry - and my new engine ran today for 15 whole minutes. First time since the late 1980s.

That gasket supplied by the vendor is very hard, and I can't imagine how it can be compressed enough to form a seal without stripping the brass threads - as I did.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard E Moore Jr. Pickwick lake Tenn. on Wednesday, September 21, 2016 - 04:33 pm:

Hey Stan. Got that OF today. Big plug in the bottom of the carb is missing, throttle shaft is frozen. Is this parts you may have or make? I'm not even going to open it up but the float at least rattles around. Will send out to you this week. Thanks


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