I think my 727 is fried. Now I'm at a crossroads...

None of the lines are kinked, but I can’t rule out the possibility that they might be close to a header in a place or two. I thought about the overheating scenario, which would explain why it would only do it after a hard run, and would progressively get worse as the fluid level dropped.

I really need to get my coolant temp gauge working…because I feel like the engine might be running warm.