[Steve S]

My 65 Impala with OEM SBC has a short water pump that locates the 18" fan only 1/2 blade's width into the fan shroud. I think the OEM fan clutch is centrifical. I've been told the fan is supposed to be only 1/2 in to avoid a wind vortex that reduces airflow. I'm swapping in a GM Ram Jet 350 crate engine with a long pump. I'd like to keep the long pump to locate a fan completely inside the shroud for better safety. I've heard that a fan with a thermal clutch is designed to be closer to the radiator & fully enclosed by the shroud. First, is this true? Second, are there any disadvantages with a thermal clutch? Third, what is the correct diameter of such a fan for the 19 1/4" id shroud? Fourth, how do I find such a fan & clutch? The GM catalogue only offers a 19 1/2" fan for the Ram Jet.

 

[Steve S]

Correct size & type of radiator fan & clutch

I made a mistake. The existing clutch has a coil spring on the front so it must be a thermal clutch, not a centrifical.

 

[Steve S]

Correct size & type of radiator fan & clutch

vetteman, you're right. The OEM cooling system works great. However, I've seen later cars like my 84 Lincoln with a clutch driven OEM fan that is fully enclosed. The fan blades have an entirely different shape than the 65 Impala. I'd rather have a fully enclosed fan for greater safety while working on a running engine. I guess I'll have to live with it since, even if I found such a fan in a later Chevy, I don't know what the min & max diameter clearance between the fan & shroud is for it to work .