454 Overheating

New 454 overheats after warmup very gradually. Have new everything, High Volume Pump, Aluminum Radiator, Brand new engine, New Thermostat, hoses. Ran compression all at between 248 and 250 lbs, Tested with 15 lbs in cooling system, no leakage, no water in oil, no oil in water. Engine runs fine until about 240 degrees, no misses, starts easily, shuts off fine, until very hot. Have good movement of coolant in radiator. Plugs a little fuel fouled, none more than another. runs for about 15 minutes before steadily climbing about 2 degrees per minute until too hot. Any ideas, other than start over?

Do you have an electric fan? I had to get one for my Caddy with a 454 but I so live in So Cal and I was fine until I ran into hot days and tons of traffic. The electric fan did solve the problem. (I have had a bad thermostat right out of the box before.):confused:

Check what Streets said too! ;)

Lynn

It could be that it's a new motor and new motors make a lot of heat because of increased friction by pistons on freshly honed cylinder walls. Retarded ignition timing causes overheating. Lean fuel/air mixture, maybe? And, 250lbs compression is a lot. Most gas engines run 150-185psi. It becomes a diesel when you get above 400psi. Do you have a shroud on the radiator? Some of the old 'vettes didn't have one and that caused overheating.

Issue was retarded timing, but also need to add fuel Octane boost. The engine is an LS7 at 12.5 to 1 compression, wants more than 94 Octane. Retimed at 4 d BTC like supposed to be and then added 104+ and I can keep it at 180 degrees moving, and while in traffic I can turn on the electric fan to drop it from 210.