47-55.1 hot 305 post radiator swap

[MiraclePieCo]

With what you've said so far I'm cautiously optometrist that you don't have an overheating problem at all. I suspect your temp went to 200 just because there was hot water simmering in the block for 20 minutes without benefit of going through the radiator after you shut the motor down.

BTW, I always use a "Spill Free Funnel" when changing coolant. It enables one to burp the air from the system and perfectly set the right hot coolant level.

https://www.lislecorp.com/specialty-...ree-funnel-606