There is a ~3/8" ~fine thread hole in the top of the head on the carb side of the valve cover , in the valve cover flange surface, middle of the head (front to back). Is this a mounting hole for a head temp sensor?? what thread pitch?

We got our slant 6 fired up and running and found several water leaks. This small hole was not leaking, but it was bubbling and steaming a bit. it looked like more steam that one would have if we were just boiling off a little water in the hole, meaning it seem to bubble and steam like it was a small crack into the water jacket??

I'm assuming we could just run a bolt in to seal it off, or install a temp sensor or ???

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Dan H
Dudes Ex Machina

Are you looking at the 2 raised bosses, just outside of the valve cover?
(one near the center and other one toward the rear of the engine)
These threaded holes / mounting points are used to lift the engine / trans assembly, for installation into the vehicle.
They are 3/8-16 unc threads
DD

Yeah, I think that center one is the one I was referring too. OK, its just the lifting hole. So we can bolt that closed and put a little sealant on it for now.

Thanks very much for the picture and the help.

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Dan H
Dudes Ex Machina

There is a third hole on some heads. Back two are mounting points like doc mentioned third is for temp sensor.

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75 dart custom, 225, >10.5-1, hurricane, 500holley, erson cam, 904, 8.8 ford 3.55 or 3.91 aussielocked, 17" steelies, and much more.

There can be a couple others in that location if you have a 1981+ head...

-D.Idiot

The two middle holes shouldn't need anything put in them. They don't go into the water jacket. If you have coolant coming out of the middle holes then you have a problem.

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Casually looking for a Clifford hyperpak intake for cheap.