The cooling section needs a little more info. I have already ruined a good 6.5 from running it hot enough to scuff and crack a piston due to a fan clutch that would not stay locked up while towing. The 88-99 body style has a serious airflow problem through the radiator due to aerodynamics. This makes a working fan critical.
First it needs to be plainly stated that a fan clutch is garbage after 5 years old. They loose 200 RPM per year due to wear and viscus fluid breakdown. Their holding power at full lockup is also reduced by age. Any sign of leakage esp around the spring is good cause to replace the unit as it no longer has enough fluid to maintain full lockup. Yes, they will act like they lock up just fine, but, unless you measure the fan RPM and water pump RPM at high engine speed you don't know how much it is slipping and good luck getting the fan clutch hot enough for full lockup in the driveway/shop.
Perhaps it is time to request a special calibration thread on fan clutch. Myself I have not seen the disadvantage of the HO balance flow issue, rather the system delay to get that damn fan up to speed is more of a concern as temperatures simply run away till the fan locks in. To keep the engine from running over the 210 mark you have to shift the cooling system temperatures down. This means a lower temp thermostat and a lower temp fan clutch. Modifying a clutch is described in your article is the only way to use a thread on clutch. (Some have had very good success at doing this mod.) Hayden clutches come on slightly lower than factory clutch set points. Kennedy Diesel sells a 4 bolt water pump low calibration clutch that used with a low temp t-stat works very well to keep you below 210 no matter the load.
When you hit a hill the fan clutch is unlocked and the thermostat is partially closed from the low throttle conditions before the hill. When you have to mash the throttle to the floor it takes time for the thermostat to open. The engine temperature is rising fast from the WOT condition. The radiator then heats up and the cooling system is now saturated and starts to heat up with the engine. Airflow over the radiator starts to warm up the fan clutch thermal spring that opens the fluid valve in the fan clutch. But wait! There is an additional delay as fluid has to move to finally lock up the fan clutch. There is a gotcha: the fan takes longer to kick in at lower RPM. So if you sneak up on a light hill and go heavy throttle but not WOT: You don't downshift and your temperature spike is higher before the fan comes on. Low water pump RPM, slower airflow from low fan RPM's, and slower fluid transfer in the fan clutch contribute to this. (Recall the fan is always turning 10-20% of water pump RPM when fully unlocked.)
You are at the mercy of this system delay and will go from 180 degrees to 210 before the fan kicks in to stop the temperature rise. This range is shown with a Kennedy low temp clutch, low temp single thermostat, 20" 9 blade fan, new radiator, new clean R12 condenser, and 4 bolt HO water pump. Noted while towing a 28' trailer hitting a sudden 10% grade and yes slowing down at max power... Outdoor temps ranged from below 32 degrees to over 100 degrees - wrecked the truck before our summers 120 degree weather hit. 1/3 turn on the IP and 14 PSI boost that can add quicker engine heating over stock: a DS4 could heat you up faster.
Starting your temperature hotter with 190 t-stats and a higher temp clutch allow the temps to shoot over the 210 mark because temperature is not the factor - the delay to get the fan locked in is the cause of the temperature spike. Proof that the spring thermal fan clutch is not only obsolete but the wrong tool for the job with the especially narrow temperature range this 6.x engine needs to be efficient and not crack itself to death.
The only practical way to avoid this delay and not overshoot the temperature is to lock the fan in by ECT by using the Hummer hydrostatic lockup clutch. (A system not yet adapted for use in a pickup by anyone.) Otherwise you are lowering the system temperature to avoid the 210 max point from sudden load.
Anything less than sudden WOT due to a hill gives you more time and makes the delay in the system less critical. Less throttle while things are heating up reduces the max temperature spike. Your average daily driver that never has extended sudden WOT runs can live with higher system temperatures. (Fan clutch and t-stats)
