Bearings and seals. Now we are talking about water pumps. Because that is what fails in a water pump.
I never understood the obsession with IH water pump because it is "cast iron". Some people seem to associate "cast iron" with "heavier duty." But when was the last time you heard of a water pump housing break?
How and where do water pumps fail? Do the housings split into two? Crack in half? Crumble apart? Disintegrate into metal pieces? No. We never hear of water pump housing failures. We hear of water pump BEARING failures.
So what difference does it make if the housing is made of cast iron or aluminum if neither type of housing represents the problem with water pumps? The difference is that the cast iron housing adds 18 lbs of unnecessary weight to the motor. The cast iron water pump weighs three times more, at 26 lbs, than the Ford aluminum design, at 8 lbs.
The IH T444e was typically spec'd to 190 HP. Many were only 175 HP. Some were 210 HP. A few "high output" versions were 230 HP, and that was maxed out top of the heap.
The 99-03 Ford Powerstroke was spec'd to 235 HP. So in this case the Ford version begins higher than the IH version left off. Then Ford bumped the Automatic version to 250 HP, and the manual trans version to 275 HP.
Before getting into the HP vs Torque argument, consider this... spin speed. That's what wears out bearings. Spinning. And we've already established that bearings are what fails in water pumps, not housings. Leaving peak torque rpm aside then, since peak torque always occurs at a much lower rpm, let's look at the spin speed at peak HP.
The IH T444E makes it's maximum HP at 2,300 RPM. The Ford makes it's maximum HP at 2,750 RPM. The Ford motor is spinning 500 rpm faster at peak horsepower.
The engine speed on the IH redlines at 2,600 RPM. The Ford redlines at 3,300 RPM.
The medium duty trucks and school busses are speed limited to 65 mph. The Ford pickups are speed limited to 94 mph.
Which water pump bearing can be expected to spin faster at peak power?
Well, I guess the bottom line is: If YOU can't see any gain to putting a Navistar pump on your truck, THEN DON'T DO IT!
With regard to your horsepower comments: as it relates to the cooling system, it's the radiator that would have some (or more) bearing or effect on a horsepower rating, not the water pump. The pump just moves the coolant...It's the radiator that's doing the [cooling] work.
"Spin speed": The pump's RPM is more of a function of the pulley sizes rather than the actual engine speed, for a given engine/setup. In my case, neither the crank nor pump pulleys were changed from the original Ford configuration, therefore the water-moving aspect (i.e. pump RPM) is the same as the original pump. Still staying cool, though.
"Bearings" are NOT what usually
fails in a water pump. It's the shaft seal that USUALLY fails first, causing a leak. Bearings do fail, and a failed bearing can cause the shaft to wear the seal, which then (again) leaks. But most failures are an "...Oh S--t, my water pump's leaking!"
And you're right, the aluminum vs. cast-iron thing is really irrelevant. But I'll be damned if I can find an aluminum pump with the coolant filter built in!
As far as bearings go: well, only time will tell. I just know from experience (wrenching on these engines) that very few Ford pumps go more than 125-175K mi. Yet the Navistar pumps will go 250K +, so something's different, and it's not just engine/pump RPM's!
Thanks for your comments though...