How Do I Prevent Low-Speed Overheating on a 500HP, GM LS3-Powered Datsun 240Z on 110-Degree Summer Days?

Mike Mileski from Tucson, Arizona Asks…

- Marlan Davis

Q: Marlan, I have a 1971 Datsun 240Z with the LS3- based 6.2L, LS376/480 crate engine in it [current version GM PN 19370411; 495 hp at 6,200 rpm, 473 lb-ft at 5,000 rpm—Editor]. I live in Tucson, Arizona, where it regularly gets up to 105-110 degrees F in the summer. I have a really good aluminum radiator in it with a SPAL 11-inch dual fan-and-shroud puller assembly (SPAL PN 30102052) rated at 2,750 cfm. The radiator size is about 24-inches wide x 16-inches high, and I can’t go any larger due to the frontal dimensions of the car.

As long as I’m going at least 35 mph the engine temperature stays around 190 degrees (the thermostat is a 180-degree unit), which indicates to me that the radiator by itself is adequate. But when I have to stop or get in slow-moving traffic, the temp slowly starts to creep up. For that reason, I’m very hesitant to take it out during the summer because I’m petrified about getting caught in a traffic jam and overheating. There just doesn’t seem to be any fan setup that offers any significant improvement in cfm flow that I can find for my size radiator.

I have a special air shroud which vents the air directly out through two large holes at the front of the hood after it passes through the radiator, and even that hasn’t helped.

What if I added a similar pusher fan assembly to the front of the radiator? Would that help significantly, or would it just block more air and make it worse? Inadequate airflow when stopped is my main problem. What are your thoughts? Are there any suggestions you can offer or am I just out of luck?