Some things that haven't been mentioned:
Are you running a 50/50 mix of distilled water and glycol? Everywhere I go in Europe I've only seen unmixed antifreeze. You can go upwards to 75/25 water/glycol if you keep it in the garage. This will help transport heat.YES!,Water is the best, but you need to protect the water pump seal, and of course "Keep it from freezing" lol
There is a product called "water wetter" that helps remove bubbles in the system and will help transport heat. For me this is a last resort and is very expensive, especially when you get a leak. Really this overheat should be an easy fix
Is your lower rad hose spring full length?
Are you positive that the system is holding pressure? It must hold the pressure indicated on the cap. The hoses should be swollen when at temp. Not limp. If it vents at 8 psi, you'll never get it to stay cool because it's boiling.If it vents that's true, but;he didn't mention venting. I run a 7psi cap no problem.
Never run an engine long-term without a thermostat or a gutted thermostat. It takes the engine longer to warm up or even warm up at all. Increased wear is not what you want in a 408 that already sees increased wear vs stock stroke.Except for test purposes
You need to change the oil if it hit 250+ maybe even going with a synthetic oil. It holds up better to heat breakdown and wicks heat better as well.Just cuz the water hit 250 doesn't mean the oil did
I'm in favor of mechanical fans with a big fat shroud and the griffin radiator.Me too
My fan is even underdriven...Mine too
I completely agree with lowering underhood temps by wrapping headers, and using a scoop or some other hood vent. It's hard to take outside temps and push it through a radiator and efficiently cool it down if the underhood temp is hotter than the coolant. That's very true
