hi i have 2 90 SC's i just replaced head gaskets on, both deck and heads were not warped, they were within spec when checked with a straight edge, but for some reason they both have pressure in the cooling system right after you start it, one kept pressure for a few days after it not running, i used felpro head gasket set with new head bolts and torqued properly, i cannot figure it out, and am going to lose my mind if anyone else has this problem or has seen this problem please let me know, again i am going crazy haha, thank you all for your help.