Slant 6 Overheating

Hey dartman, glad you were able to solve your issue. Is it cool to hijack a thread that's been dormant for a few weeks? :P

I also have a /6 225 (71 Scamp) that for the life of me I can't get cool under load. I can drive around town all day regardless of outdoor temps, but if I get over 50-55mph, the radiator pukes. The motor is (to the best of my knowledge) completely stock with 20k miles on it. I drove it from its original home about 100 miles and had no problems, let it sit for a year, and then it just kept overheating. Now I'm determined to figure out what's going on.

Anyway, I've set the timing to 0*, checked the dwell (can't recall what it is, but it was within spec), adjusted the carb, replaced the radiator and cap (16#), replaced the water pump, replaced the thermostat twice (first with a 180, now with a stock 195). The radiator shroud is missing (if it ever had one?), but since the engine is not overheating in traffic, I don't know if it could be contributing.

The car feels like it lugs just a little bit at steady cruise, but it still has get up and go if I stomp on it. Should I advance the timing from stock? On the off chance one of my cylinders isn't firing, I got a spark tester yesterday and plan on checking that as well. At idle, the car bounces a little bit more than I would expect from a smooth idle.

Thanks, guys. I really want to start/continue driving my 71 to work. My parents bought it new and special ordered it with a really horrible color combo that according to the trim tag required special authorization - LOL. I remember hating to get dropped off at school in that thing, but I'm really attached to it now. :)

-John