Overheating 400 ci

hey guys looking 4 some advise. I have a 77 pontiac grand prix. The motor came out of a 68 bonneville. Its been punched .030 and crank work. Electric fan I measured the gap between the water pump impeller vanes and the plate. Its now .030". I put 2 new thermostats in and no air pockets. I also put water wetter in. It overheats cruisin down the road.50mph plus. There is a coolant nipple coming out of the back of the head, i have this connected to the heater core and the other line to the water pump is this right? If the head gaskets were on backwards, would this block the water passage? If so shouldnt i have coolant in the oil? Someone help Please! I dont want to burn the car to the ground!  

Pontiac head gaskets are symmetrical, no front, no back, no top or bottom, so no matter how they are on, nothing can be blocked. Yes you have correctly hooked up the heater core running from the head and back to the water pump.

Your problem is the electric fan. The average electric fan sold by any speed center for $70 - $150 only flows around 700-800 CFM. A street car requires a real electric fan. At about $250+ you will find fans that flow 3200 cfm such as a Spalding.

700 cfm will keep an engine cool at idle and low RPS at 35mph. At highway speeds the engine is running much faster, more friction, working harder, thus burning more gas producing more heat. The pump is turning at a higher RPM, but the heat is not being pulled out of the rad so you heat.

First you need at least a 3 core rad, preferable 4 core that is in good shape and new or flushed out. Second, get a fan that is over 3000 cfm. Make sure your Alt is 80-120 amp as a fan like this will pull 20-30 Amp. It is also preferable to use a shroud. A 14" fan will only pull air in that 14" area, thus 70% of the rad is not being used. Adding a shroud or buying a fan with a shroud will pull the air evenly over 100% of the rad.

If this is not a race car, then you can save the $400 on a good electric fan setup and just put in a mechanical fan with a factory shroud.  

Thanks,It is the fan. I did not mount the fan. It was pushing not pulling air. I tried to reverse the polarity but the blades are curved so i re-mounted the fan. Still runnin about 220. Im going to the speed shop tomorrow, to look at a better fan. Thanks for your help.