Coolant flow
I have done the research on cavitation. And not just with automotive people. Cavitation is very rare unless the inlet side of the pump is restricted. Unless the hose is collapsing or some other issue is restricting flow to the pump the number of blades isn’t an issue. You’d have to show me real world examples of cavitation in automotive water pumps that were caused by too many blades.
180 degrees is the HOTTEST any of these engines should run and that’s not “left over” from my drag racing days. You are hung up on your number because you are stuck in your new car, hot coolant days. The “modern“ engine is nothing close to what we are discussing here. No one is using knock sensors and **** like that to pull timing on the stuff we are talking about.
Making power is about cylinder pressure. Cylinder pressure makes heat. Heat is power. Heat also promotes detonation. New (or “modern” like that means better…it doesn’t) engines deal with detonation by using knock sensors. They are also concerned with cold start emissions (I’m not), getting the cats lit (again, not a problem we are discussing here) and certain emissions levels (again, not relevant in THIS discussion) so trying to marry “modern” engine operation conditions to what most of what we discuss here is LUNACY.
But, here is the real clincher. Wait…I need to mention I haven’t done any work (as far as tuning and such) on any “modern” engine newer than about 2003 so keep that in mind…the real clincher is dropping the coolant temperature even on those engines increases power.
Now take off the EFI and all the related **** and drop a carb on one of those and run the coolant temperature up and see how fast detonation drops the power. It will start killing 20 HP so fast your hear will spin. And you have to add fuel and reduce timing (which makes more heat in the exhaust) which makes less power.
So get out of your head that coolant temperatures of 160-180 are a “drag racing” thing. Most drag cars have undersized, piss poor designed cooling systems that don’t control engine temperature like they should. That’s the big reason why drag racers (and corner turners) gain power when they switch to alcohol. They need the heat to vaporize the 2.2-2.5 times more alcohol than gasoline. Had they spent the money and time to unscrew their cooling system they would likely see little, if any gain from alcohol. And when that happens they see very little savings in fuel costs since it takes over twice the alcohol to make the same power as gasoline.
When I was tuning circle track engines (another group of people brainwashed that hot engines make more power) the FIRST thing I did after unscrewing their tune up was to make them buy a better radiator, a better pump and made them either sell or scrap their under drive pulleys. It was a fight for the first couple of people.
Once I was done, those guys finished 1 and 2 in points and neither one ran over 170 degrees. And all the long time smart circle track guys told them the engines would be junk when I did the freshen up at the end of the year. Of course, those morons were wrong.
I made them come to the shop on the weekends and they took their own junk apart. Then they watched me measure everything. We could have reused every part.
I have debunked the cool(er) engine temperature kills engines lie so many times its just stupid that it keeps coming up.
Again, these customers were running mostly on 3/8 dirt but they eventually went to 1/2 mile pavement. So the aero stuff doesn’t apply to them like it would to a car capable of more MPH, which is EXACTLY why cars at that level keep the coolant temperature as high as they do. I already talked about that somewhere else.
There is zero downside to running a cold(er) engine. I’d run mine cooler but at temperatures lower than 160 I can’t get defrost to keep the windshield clear.
Once again, you're looking at this whole thing through the VERY narrow window of maximum power output on a dyno or at the drag strip. All of your examples are drag racing or dyno's, and it's why you're so dead set on this (and wrong for other applications).
I know you're well versed enough in building engines to know that max power output is not the only way you can tune. It would be very different from a maximum efficiency tune, for example. And you throw out "drivability" too, and for street drivability there will be very few engine builds where tuning for maximum power will actually give you the best drivability. Tuning for mid range torque, for example, vs maximum hp, would give you a much more street drivable car. And that's not gonna push the limits of detonation. For that matter, a lot of engines in these cars are no where near pushing the limits of detonation.
As I said before, drag racing is quite possibly the ONLY automotive motorsport that runs coolant temperatures below 180° or colder. There are much more exotic engines that don't do that which go A LOT more miles than any drag car or even most of the "street" cars discussed on this board.
And you can't just say this is limited to 50 year old engines, because I've seen you give this advice to guys with modern engine swaps. You're giving out advice that's good for the niche it belongs to, but is not necessarily correct for everyone that you're giving that advice to. There ARE disadvantages to running too cold. Just because you personally haven't seen it doesn't mean it's not true. You're not basing your advice on engines that are meant to go 100k+ miles. And yeah, most people don't drive these cars like that. But your advice is not absolute. It's a single way, out of MANY ways, to tune an engine.
I'm not gonna argue with you on this. I'm sure what you do works for how you build engines and how you drive. But it's simply not scientific truth that the way you do things is in fact best for all engines and all applications. For a drag car or a street/strip car, sure. For anything else, sorry, but no. Your experience in this, while valuable, is anecdotal.
