OK, that's two votes for compression check. It hasn't been losing coolant, but this overheating issue that's cropped up in the past month makes me wonder. Normal driving around town is fine. It's only when I get on the hi-way for an hour that the temperature climbs. I was figuring with 450,000 miles and original rings that top cylinder lubrication is probably not happening at this stage (time for the 50 w oil in the crank case). The head is the original factory head and baby this one's been beat. The last time I had it off one exhaust valve had a hole burnt right through it and another had the seat melting into the head; and it still ranà Lot's of hydrocarbon in the emissions though. The shop that reworked it did an amazing job replacing that valve seat. I thought the head was done for, but that was five years and a lot of miles ago. I know how tough it is to kill these engines. They may not run well all the time, but they keep running. I'll do a compression test this weekend and post the results. IÆve got a multi-tester so IÆll check the resistance on the temp sensor too. Thanks for all the feedback and advice.