Just a couple of thoughts.

The first is are you SURE it’s overheating. I have found some gauges, especially factory electric gauges on older vehicles to be very inaccurate. Factory tolerances, wiring and grounds that have degraded over the years and replacement sending units can all factor in to this.

A few years ago I spent a huge amount of hours and fair amount of $ changing fans and putting in a new radiator in a car only to find out the car was really only running at 190-200 degrees. Another one was my DD 84 El Camino that has a factory gauge cluster and the temp gauge in that reads a constant 30 degrees hotter than the actual temperature is. After changing the sender a couple of times and not being able to find a replacement gauge, I've just gotten used to it. I have found that a temperature gun is a great tool to have to start the diagnosis process before spending a dime on hardware (it's a lot cheaper than buying a new radiator you don't need).

The second thought I have is that what you are describing sounds like at speed the blades of the flex fan are flattening out and not drawing enough air thru the radiator at speed (as you slow down the blades curve more and start drawing the needed air). Just from my experience (other may vary), aftermarket flex fans often have blades that flatten out too quickly. Personally I prefer to use Ford 6 or 7 blade flex fans if I have to use a flex fan....... and for gods sake don't get hung up on the little oval marking that indicates who made the fan over keeping the engine cool.

Personally I prefer a mechanical 7 blade fan with a HD clutch (the thick one speced for BB Chevy trucks) over electric fans. The fan locks up at 210 degrees and with the factory 7 blade fan and shroud I doubt you have any more heating problems.

My problem with using electric fans is that generally speaking the cheap ones really don't pull sufficient air, and the better ones can put a pretty good strain on an older electrical system.

Anyway, that's my 2 cents.


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