Good info about cooling and fans. I'll have to check my flex-fan.
The 71 had the same issues with cooling until I converted to a 5-speed.
Alot of heat was coming from the old C6, now it runs normal temps.
Adding a trans cooler would help alot too (if you still have an auto trans!).

 

urban cowboy,

What gears are you running in the rear? Your normal operating RPM range seems pretty high?

 

Fan clutches do not explode. The clutches may die, but the clutch housings are not prone to failure. I've never, ever seen or even heard of a fan clutch coming apart. Even if one were to come apart, it wouldn't result in shrapnel being thrown around the engine bay. The worst that would happen would be the fan spinning off (in one piece) and taking out the hoses and radiator.

I have seen the results of flex fans coming apart in several instances, and several people I know have seen it more than once. It happens, and it's extremely dangerous when it does.

The reason mfg's say fan clutches aren't rate for high rpm applications is that they will have a tendancy to burn out faster under those conditions. It's not a safety issue, like flex fans. They just don't want to warranty a bunch of bad fan clutches simply because racers are using them in front of high winding engines. I imagine I'll probably have to replace mine at some point in the next year or two, but I can live with that. It's cheaper, easier, and safer than dealing with a flex fan that came apart.

 

RPM operating ranges are relative to engine type, power band, air flow, and gearing. I run a 3.50 rearend gear which is about at short of a gear I dare put in and still keep traction. If I ran a taller gear, I would be cruising out of my power band for the cam which is a terrible idea. This is not a commuter car or DD. It is a hotrod, so I do not care about gas mileage much. I have all ARP and forged parts so it will take the abuse just fine.

I have plenty of power and torque related issues and parts breaking, but really the only issue I have now with the rpm range is the fan.

At 75mph my rpms are 3300. I run 26X10.5X15 MT Sportsman Pro tires. I run a 280 duration roller cam which comes in around 3000 and drops off about 6300 at least that is what my ars sensor tells me. Because of the lack of air velocity this engine setup has at lower rpms, this motor behaves much like a prostock car in that it needs rpms to atomize fuel and run properly. I have gotten it to behave a little better through my carb tweaking but that is a totally different story. I idle at 1200, leave stop signs at 2000 and the car never drops below 2500 unless I am coming to a complete stop. It spends a good amount of time above 4000 and I shift at about 5000 on a cruise and 6800 on a performance pull.

Star, I respect you, your opinions, and your knowledge very much. I am going to have to disagree with you, though, on this point. I think you are discriminating against flex fans as a whole when nothing is known about the flex fans that you have seen come apart. It is simply hearsay. We do not know if the flex fans were rated for high rpm use or if they were damaged somehow from age, wear, etc. All I am saying is Flex-A-Lite 1300 series fans are rated for 10k rpm and the clutch fans I have found are rated to 4k. I need a fan that is rated at least to 6k to feel comfortable that it is going to last a while. God knows if things are not up to snuff, they do not last long around this motor!

 

Fair enough...but I still think you're taking your chances with a really nice car. I'd just hate to see you put a hole through your hood.