Im wondering if I should pull the risers and see if I got all 4 slots open like the merc bullitin. If I do that Im half temped to go back to the restricted.. Keep it at 900-1000 rpms, zero issues
I think You should be running the non restricted gaskets with your style thermostat housing ( cold manifolds). As AD said that isnt the issue thermostat should hold back water enough to keep it at temp. i would guess you have a mismatch between the thermostat, manifold crossover, thermostats housing, and or thermostat sleeve . Somewhere in there water is getting by where it shouldnt
