Thanks for the response.

I didn't have the engine rebuilt, it was the owner before me, but I assume your right and they used the original parts, ie. oil pump.

I still don't understand how the actual gauge in the dash could be the problem, when all it does is get a signal from the sender, based on a difference in volatge and resistance within the sender. If it works fine on a cold start and then drops out with some minor heat, how can it be the gauge? The sender is what is sitting on the engine and taking a reading.

Does anybody have any experiecne with the oil pressure sender?

Thanks.