New/Repro YF carburetor for the 300 six

This is an odd one... Cory, do you think there was any way the plastic float was expanding and rubbing on the side of the bowl or catching on anything that would prevent it from floating? Any tight clearances? My other hypothesis might be a needle valve that is tight in the bore but I don’t think the metal float would fix that unless it somehow has more lift than the plastic one? 🧐

If I had to guess I would assume it was the float level was the issue and not the plastic at all, and the metal float was just bent for a more correct level? I talked to a local guy that completely removed the flapper valve in the exhaust manifold, so I sort of ignored that as a potential issue. Anyway, there is also the issue with the pump...the one I’m running is rated at 5.5psi, and the other pumps are rated for 2psi. I read on Mikes carburetors that the YF should have about 4psi max? I’m going to change the pump anyway.

Replacing the pump is a better solution than installing a regulator?

Maybe the plastic float needed it's tab adjusted?
Is there a way to check float level on that carb while running?

I’m still perplexed as to how float adjustment or lift pump pressure would change as the truck came up to operating temperature 🤷‍♂️. I guess it is a moot point if the metal float fixed the problem, but it would be nice to know what the issue was in case others run into it.

ArdWrknTrk wrote

Replacing the pump is a better solution than installing a regulator?

Maybe the plastic float needed it's tab adjusted?
Is there a way to check float level on that carb while running?

Well, I'd like to install the correct (lower pressure) fuel pump just to keep things consistent, but why it was behaving the way it was I don't know. It ran like a top, but once up to operating temp it would leak profusely...so I honestly don't know. I installed the metal (heavier) float, and boom, all is well.

If the carb was leaking I suppose that is enough to say the bowl level was too high while running.

I understand not wanting to question the answer, and simply find the correct pressure pump.

Ok next issue. I have a leak at the 1/8” NPT fuel inlet at the carb. I’ve tried it with and without Teflon and it leaks both ways. I can’t tighten it any further without cracking the aluminum. I’m going to order the lower pressure pump regardless, but what can I use to seal up the pipe threads?

Taper threads are supposed to be self sealing. Teflon tape is lubricant so they don't gall.

I would try Loctite PST.