[mitchntx]

Glenn has done tons of research on this and we are both about to the point of have custom machining done.

Autometer guages have a sending unit that is 1/8" NPT.
An LS1 motor has ports machined in, but are 12x1.5 metric.

Sure there are adaptors, but the wall is so thin the adaptors twist off with MINIMAL torque. And by that, not enough to crush a seal enough to prevent a leak.

Why don't they make a 12x1.5 sender?????

The stock sender ohms out WAY different ... almost 1K ohms lower than the AM.

[mjf454]

I think we are talking about two different adapters. The one I used is a part #2268 and it is a 1/8" to M16-1.5. It fits in the large ports of the block {there is one behind the alt, and one at the rear of the block} I am seeing now that you want to use the small port in the cooler adapter above the oil filter. The 2268 fits in the head plugs, if you are going for water temp. It is the same size as the plugs, with a 1/8" hole tapped in it.