Let me start by saying that we have had zero bearing failures from engines that we built with our methods. We have hundreds of engines around the globe running for years on high power, high rpm operation with zero failures. The only ones to ever fail are when customers insist on reusing certain parts: Rods, oil pan, oil pump, oil cooler etc.
When we did airplane engines we had NUMEROUS oil pump relief valves stick from small amounts of particulate left over in the oil pan. Regardless of how well it was cleaned, there is ALWAYS metal in it.
If a customer comes in with a spun bearing, we won't work on it until he agrees that he is changing:
All our engine builds use new components so no more worry with resized rods, turned cranks etc.
Heads are disassembled and thoroughly cleaned.
All that is fine and dandy, but the most important part of an engine build is getting the clearance correct. ALL the clearances. The main bearings are more important than rod bearing clearances. When building engines with used blocks the mains are ALWAYS over 3 thou and sometimes closer to 5. If your builder says they aren't, uses HX bearings or something else, he's wrong. In hundreds of cases I have Never ever ever seen a used case come out with proper clearances using standard size bearings. Now some logic has to be used here in that most used cases are over 30k miles. If you have a 5k mile case, then I suppose the mains could still come out. However, we don't get 5k mile cases. I can't imagine many people do.
Now you're probably wondering "wait you said you use all new components, but now you're saying you use used cases".
Let me clarify:
1. For new builds we no longer use old cases. This policy has been in effect for about two years. We used to rebuild a lot of motors but they took more money and time than they were worth.
2. We only use used cases for sleeved, high horsepower cases. In each of those cases we mill the inside surface of the case flat and shoot the mains again. They are NEVER even close to being flat when we get them. This is because the engine has been cycled, seasoned and stress relieved. This is why the mains are always big on used cases. That is the same reason we use them for sleeving. We don't want the cases to wander after sleeving.
DON'T USE 5W-30!! Read the owner's manual. It even says not to use 5w-30 for anything other than commuting and daily driving. If you're trying to make power on 5w-30, you'll be spinning a bearing.
Don't use Mobile 1. Why?
1. Mobile 1 engines are always some of the cleanest engines when we take them apart. No oil residue anywhere. That makes no sense to me. If your oil is adhering to surfaces and providing lubrication there should at least be a little residue.
2. The only engines I have ever seen with bucket or cam failure have been Mobile 1 engines.
3. I have seen oil tests that cover film thickness, viscosity and friction over the temperature and pressure range and that oil just doesn't cut it.
replace it once or replace it twice
do it right once
don't use 5w-30 or mobile 1