Not to muck up Larrys 300 build thread any more I am going to start an new one.
1st I would like to say that I wasn't trying to be disrespectful to anyone (esp Paul) but did want to understand the thinking.
I did a deep read on the subject, and found we are both wrong. Liner cavitation has nothing to do with the water pump at all. Not design, not placement on the block, not how well it bleeds itself of air, nor air itself.
We were both partially correct and partially wrong. Paul is correct that vaporized coolant, not air, is the cause. It isn't due to flow or pressure however, according to what I have read on the subject.
Liner cavitation is caused by high frequency sound wave from the liner itself, cause by the combustion and movement inside the liner. When these high frequency sounds get transferred from the liner into the coolant, they make high and low pressure points in a wave, as the liner resonates. When at the low pressure stage of the wave the coolant can vaporize and when at the high they "burst" back to liquid. This, over time can etch the liner in a tale tail pin hole shape.
For this reason, cavitation damage is limited to one plane of the liner, and 90 deg around the liner there will be none, it is all in how the liner resonates. This also explains why it occurs more or less evenly across all liners in the engine without regard to how close or far they are from the water pump. If it were caused by vapor pockets circulating in the coolant, we would expect the damage to be random around the outside of the liner. It is also why some manuals state "with minor cavitation damage, the liner can be reused if turned 90 deg in the block".
Centrifugal pumps can not pump air efficiently and even less so with a liquid "head" above the outlet. As stated it is why they are not "self priming". For this reason, there is a way provided to expel air when the outlet is below the top of the impeller housing. Eliminating any trapped air is important, but has no effect on liner cavitation. It can effect the pump itself and other parts of the engine. It is partially why all trucks for over 50 years use a "bottom fill" system (shown in the 300 thread as a Marmon attachment) so the coolant rises from the lowest point in the engine and pushes out the air as level rises.
Paul stated "I must have an open mind to learn" and I do, which is why I ask anyone to back up their statements, I can't learn if I don't know the "why". An open mind lead me to a few hours of reading on the subject. I have already apologized to Paul in the 300 thread if I seamed a bit too "confrontational" but I need to understand the "why" of something to be able to retain it. His
If you want more info or possibly a better explanation then I can give, do a web search for "causes of liner cavitation in heavy diesel engines" and select the ones Not from some YouTTube, but from engine mfg.
To quote Paul "
So cavitation occours when the liquid, in this case water, separates into gasses
Oxygen and hydrogen in the case of water
This happens when the delivery side of the pump isn't restricted enough or supply side is to restricted "
It isn't that the coolant separates into Oxygen and Hydrogen or even that the mixture of antifreeze separates at all, but rather that it changes from liquid form to gas form while still being coolant, this happens at the minute scale where the wave caused by the high frequency sound from the liner meets the coolant on the outside of the liner. Much like an ultrasonic cleaner does. It does this while at pressure inside the block. Cummins low flow has a block coolant pressure of ~45psi @2100 rpm! That engine still has liner cavitation issues. It isn't that the flow is restricted in any way, either on the low pressure or high pressure side.
Until I read up on it, I never really gave a thought to why it is on one side of the liner and 90 deg it doesn't happen, I knew that to be true, both from reading and pulling liners out of engines, but now I know the "why" and it help me to better understand the problem.
Likely more than most want to read or know, but I did put in the time to understand it.
The most important point I learned is the "vapor bubble" is both created and destroyed at the liner itself and not the result of being moved about by the circulation of the coolant.