70 Nova overheating problems!!!

OK, I transplanted a new rebuilt 402 BB in my 307 car, I have 2 radiators available, a 2 row aluminum (a 1" row and a 5/8" row) and a 3 core Modine both for a small block core support. I have tried both and the car still overheats. I have a 180 thermostat which I tested on the kitchen stove in a pot of water to make sure it opened at 180. I fired up the car without the thermostat to make sure the new aluminum water pump was working properly, it is. I got 2 new radiator caps, a 13 psi and a 16 psi, pressure tested both to make sure they held pressure, they did. Going down the road over 45mph the temp stays at 195 on my new autometer gauge, below that speed the temp starts creeping up. I am using a modified stock radiator shroud (notched for the alt pully and ps pump pully nut) and a 17" flex-a-lite mechanical fan. Just sitting in the shop the car's temp won't even hesitate at 180 when the thermostat opens it just keeps on climbing. The engine timing is set at 5 degrees BTDC, book says 4 degrees BTDC (for a stock camshaft) so that should not be causing any problems. UPDATE: I reset my timing using a vacuum gauge to power time the engine (RPM at 2000, vacuum advance disconnected, advance distributor to reach highest vacuum reading then retard timing 1 inch of vacuum then lock distributor down, then use timing light to check timing before reinstalling vacuum advance line. Timing was at 10 degrees BTDC which is consistance with an aftermarket camshaft which my engine has) Engine is still running hot. HELP, what is wrong????

For starters I'd say you need a larger radiator. Outside of that I would install an electric fan in addition to your mechanical fan, you can pick one up for about $50 and it will fit with the mechanical fan still installed. Also consider putting in some water wetter into the radiator, this will assist in keeping the temp down a little. Make sure your stat is not installed backwards. Also, make sure nothing is blocking airflow through your grill to your radiator. And you may consider installing a air ram of sorts somewhere to get some forced air into the engine compartment while you're driving. You could remove one fo the parking lights, run a duct with a screen covering it to keep junk out and just run the duct into the engine compartment. You could really install it anywhere andany way you'd like. Whatever looks good to you & gets additional air into the engine compartment. Good luck to you.

Dennis321, I sent the 2 row aluminum back and got a 3 row aluminum. I have an electric fan but have not mounted it yet. I switched the temp gauge sending unit from the stock location in the cylinder head to the intake manifold and the engine runs at 180 now but have yet to try it in the summer heat. Thanks for your input.

Sounds like you're on the right track. Best of luck to you in the summer heat.