Thanks for the tips. I just didn't know if the radiator would suck in too much air if the overflow wasn't sealed. I'm not sure how much suction a radiator will even cause. I've tried it without the overflow, but I think I filled it too full (almost to the top). When it got hot it spit antifreeze all over the engine bay. Does anyone have pictures of these fillers? These may be the missing link (or at least one of them). What do you think about thermal clutch fan vs. clutchless? My machine shop guy told me to go clutchless, but he's not a Pontiac guy. I don't want to be robbed of horsepower if I don't need to be. Do you think running at 230 is going to ruin anything? Do forged pistons and rods have better heat resistance than stock? I'm going to buy an infrared gun soon to at least help me confirm that my temp gauge is reading ok. I think it is though because the inside of the car gets plenty warm, but I do have headers that put off a lot of heat.