Guess the race part
would today's answer to the oiling problem be a smaller diameter rod bearing? 2 or 1.88"? or is there an inherent deficiency in the oiling system at that rpm?
All that type of thing helps, but you have to get the oil out to the rods at the right time.
An example is full groove main bearings. When you use them, you get SOME oil out to the rods all the time. But you still don’t get full pressure, full flow oil to the rods at the right time.
So what happens is the full groove mains will help with rod bearing oiling up to a higher RPM than without them, but you will at some point reach an RPM where they no longer get the oil there and bang...out comes a rod.
If you think about the TIME involved, it starts to make sense. When the oil hole in the block lines up with the oil hole in main bearing of the crank at say...2500 RPM and let’s say for easy math (I hate math) that at that RPM the two holes line up for 1 second.
At 5000 RPM (this is where I get a bit soggy on the math) if it was a linear reduction in time, the two holes would only line up for half a second. But...IIRC it’s not a half reduction but more than that. Something like they are only lined up for .25 seconds.
Where are the math geeks?
At 7500 RPM (which is 200% faster than 2500) the time the holes are lined up is again much shorter. I think at that point it’s less than .1 second. Again, these aren’t real numbers. The real time is actually probably 6 or 7 digits out .0000002 or something like that.
As you keep going up in RPM you reduce the TIME the two holes line up. As that happens, the oil getting to the rods at the right time becomes more critical and you just can’t rely on the full groove bearings to save it.
Good oil pan with a 1 inch pickup (or better yet a dual pick up) is a big deal. As the RPM goes up, the restriction at the pickup gets higher, so anything done to reduce that restriction is a big deal.
Stoping all the oil leaks at the lifters is another big deal. That’s more oil being forced through the system and not leaking past the lifters.
Of course, we are talking about shifting at 8000 and higher. Maybe tomorrow I’ll take a picture of the two different styles of pickups that I know work.
