I have seepage at rim of the bowl and body of the carb. changed the gasket twice still have seepage. I have not backed off the drain valve plug while tightening the drain valve body and gasket to the bowl. I assume that the valve plug does no function except the drain the carb. as necessary Is this correct? Would backing off the plug allow more "tightening" of the valve body and stop seepage?
Sounds like the float level is too high, adjust as needed.
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Sometimes the middle of the bowl will get sunken in over years of tightening the bowl nut. The bowl should hit the carb body first. You can set the bowl flat on a piece of wood then put a socket the right size in the bottom of the bowl and hit it with a hammer to flatten it out. That way when you put the bowl on it will sandwich the gasket there first and when you tighten the nut it compresses both gaskets.
Can you lay a piece of 180 or 220 grit sandpaper on a very flat surface and sand the rim of the bowling the sandpaper?
I learned from this forum that, right out of the package, the bowl rim gasket is too small to fit into the rim flange and must be soaked in water prior to installation. If you try to install it without soaking, it will either tear, or will be distorted to the point of not sealing properly. Jim Patrick
Another possibility is a leaking float valve. That will let the bowl overfill. It can be caused by the needle not seating properly, due to an irregular surface of the needle or seat. Another cause can be fuel leaking from behind the seat due to a rough surface in the hole and a gasket too hard to seal well. The seat gaskets sold in kits are notoriously too hard, and I always make my own. Some make the gasket of lead, but so far thick gasket paper works for me.
I think gas is leaking past your float valve. Four possible causes: 1. float too high.
2. gasket under needle seat not seated. 3. Needle not properly seating in seat. 4. A spot of dirt between the needle and seat. See Steve's post above.
I love how it says to check the float valve for leakage in the Ford service manual...turn the carb upside down and suck on the fuel inlet elbow, if needle is properly seated, the tongue or lips will stick to the elbow. Imagine a modern car service manual telling you to put the carburetor on your mouth to check it? By the way after reading that I ran right out to the garage to suck on my newly built carb and my lips stuck! Doug
How does it taste? Yuk!
About like siphoning, only less.
I had the same leaking problem. It turned out the float pin was too short which allowed the float to get stuck in the open position. A trip to ACE and a brass rod that could be cut to the right length fixed it.
For checking needles and seats, we can create a tremendous amount of negative pressure (vacuum) to test for sealing on valves.
I've tested this with a gauge. :-/ Slip the tongue or a lip over the port and you'll soon know.
Tastes terrible no matter how much you clean the port. Tried it last on an IH Diesel return fuel check valve. Yuck. Spit. Spit. Yuck.
Leaks like a sieve. No prob tho.
If the NH is set correctly, the fuel will not reach the top of the float bowl and therefore the gas cannot leak out. If the gas leaks out, then the level is too high. Either the float is set too high or the gas is leaking past the cut off valve.
For an NH I believe the float level should be set to 15/64”. Just how you get it that accurate on a rough casting is another matter. The needles with a rubber (?) seal seem to fail with modern gas, so the all metal ones are preferred. However modern ones are too rough and need to be smoothed before use. IMHO
Tony, where are you getting these metal ones, seeing how the venders say they are no longer available? Inquiring minds want to know. Doug
I can answer Norm's question about the taste of the carburetor. I rebuilt my NH last week. Since everything was freshly cleaned and painted, I decided, in the interest of science, to try the "suck" test (see figure 440 in the manual!) It tasted like... fresh paint. My valve was well seated. I followed the advice of sanding the surface where the float valve gasket sits using a dowel with a disk of emery cloth glued to it.