I'm on the second rebuild of my 428, the first build lasted about 200 miles before a rod bearing self destructed. During that span, the motor ran great with temps ranging from 185-195.
It's now overheating at idle after being rebuilt a second time and I'm losing my mind trying to figure out the cause. The moment I bring the RPM up, the tempture shoots down, cruising its stone cold. I'm using a mechanical water temp gauge. EVERYTHING is the same as it was on the prior build, same timing, carb tuning, clutch fan, water pump etc. I'm running a Derale clutch fan with a factory shroud and ACP 3 row aluminum radiator.
The second rebuild consisted of new bearings, rings, hone, and crank regrind (and new gaskets of course). The machine shop built the short block, I assembled the rest. I purchased the exact same gaskets as before. I never pulled the thermostat, it's the same one that was in the motor before the second rebuild.
The head gaskets are not backwards and I did a block test to verify that there aren't combustion gases getting into the cooling system.
With the cap off, I can see coolant flowing when the thermostat opens. I've tried moving the initial timing anywhere from 8-22 degrees with no change, I left it where it ran best around 14. I even removed the PCV just to see if it was sucking in too much air and making it run lean at idle, again no change.
The only change is from a standard volume up to a high volume pump and the addition of oil restrictors in the cylinder head for the rocker arms (I'm using a massive Canton oil pan).
What gives? At idle it creeps up past 215+, but when the RPM's increase or I begin cruising it's 175-180.
