Heating up at highway speeds (only) is usually an air flow problem.
Exactly. Thats why I was looking for a tranny cooler blocking off the high pressure air at freeway speeds. He doesnt have one. The air needs to flow in and out. Being a good setup I think he has flow out. Some cars Ive seen are restricted out the back side of the engine bay, the air flow just cant happen.
Hmm.. Lean engine could cause "some" over heating, but you would see it around town too.
Kinda funny, yer heating issue is kinda backwards of most peoples. They are over heating on the city streets not the freeways. At least you are running cool on the city streets.
A severely under driven coolant pump would cause this, but you would see it even more on the city streets. Under driven pump along with a low air flow on the city streets would be a major heat issue.
Hmm, higher road speeds, more air flow, more heat?? Hmmm...
Since the top end rebuild. Same parts? Just a freshing up? Or new parts? How bout them gaskets? Head water ports or not? Water ports but a block off gasket?
Hell, I dont know. What did you do during the top end rebuild? Thats the key. What you did changed the operating temps. JR