@DrRock I just ordered one of the hot and heavy fan clutches from redline - I'll update here when I get it delivered and installed, and let you know if it seems to cool any better. I already run a 180 degree thermostat, and it manages reasonably well, but a good climb on a warm day can get it up a bit hotter. As I can generally hear when the fan clutch kicks in, I know it could do a little better. I am looking at getting my AC system working again, and figure I could use all the help I can get with cooling when I am pushing the engine a little harder.
I just installed my HD fan clutch just in time for some +90 DEG F temps here. My temp gauge creeps up but on my Sniper CTS ( which is mounted in the block drain on the LH side of the engine) I will see 210 Max on a 10min climb in second gear with RPM’s between 3000-3200RPM in 90DEG F ambient, with the AC running. I’m also running the factory 190 DEG F thermostat.
As for the factory gauge reading, it will go up to around 3mm (~.125”) below the top on the white band of the temperature gauge. From my perspective, this is perfectly fine and expected per the information from Toyota. These trucks aren’t like new vehicles that have more sophisticated thermal management. I would also speculate that Toyota did this on purpose to provide more feedback to the driver so one can adjust ones driving habits accordingly.
Overall, I do see temps running 3-5 DEG F cooler with the new fan clutch.
For reference, my engine has Chevy small block stainless valves, cylinders punched out to yield 4.4L displacement with factory pistons, Holley sniper and a Jim C. Re-curved distributor with timing set right on the 7DEG. I initially set the advance around 9 DEG but was getting some pinging so brought it back to 7 and it runs really well now. Given the distributor re-curve, I suspect that is providing enough advance in the higher RPM range to not warrant additional baseline advance. Lastly, I’ve run 4 different octane fuels ( 87, 89, 93 10% ethanol blend max and 91 non ethanol blend) in like for like driving conditions with no changes observed in engine temp or performance for that matter. Next winter I’m going to update my header to the Tri-Meki header which in theory would bring the teams down as the scavenging is improved. I’m already running a 2.5” stainless header from the manifold back but the improved scavenging should move the exhaust out of the engine bay quicker.
Bottom line is given the age, state of tune and differences that these 35+ year old trucks have, each one is unique like a snowflake. As long as you aren’t going into the red, you are fine. I’ve also checked with an IR temp gun and highest I’ve seen on my head near the exhaust manifold was 215 DEG F. I’m glad to have the fan clutch installed as every little bit helps. I’ll be driving to Colorado, then Arizona later this summer so the additional cooling will be appreciated.
Hope this information helps and looking forward to your results.
Cheers, James
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