" It's the fact that engineers KNEW decades ago that the rods need maximum oil flow at about 70~ ATDC. It moves a bit due to rod ratio but that's pretty much the standard. Every Chevy ever made has the oil timing at 70 degrees after TDC. They will oil well past useable RPM with less pressure and volume than a Chrysler. Or a ford."
I'm not saying you're wrong...you could be right....but here are my thoughts:
1) 70 degrees is a fact? According to who? I'd have to see some good evidence before I accepted that as fact.
2) We fire the ignition well in ADVANCE of when we want the combustion to take place. We do that because we recognize that nothing happens instantly...there are the usual delays. So if we want the combustion force to start at 1 ATDC we trigger the ignition at 34 degrees BTDC. So...if we want maximum oil at 70 degrees ATDC, it makes perfect sense to begin applying it a little ahead of time in order to support the development of the best oil wedge, etc. And don't forget that oil pressure doesn't cease to exist the instant the oil passages misalign...there is still a pump pushing oil through the bearing gap.
The ABOUT 70 degrees ATDC was published in some book(s) (probably text books) in the early 20th century. I suppose if one was of the mind you could search the government archives and find the research on it.
Like the principles of carburation which were well determined before the 1920’s, such was the about 70 degrees ATDC.
Look at a small block chevy. Even without priority main oiling, they can use less volume and pressure and will oil the rods at much higher RPM than the Chrysler will. And look at how it oils?
Chrysler KNEW about this...which is why they recommend full groove bearings for higher RPM operation...they KNEW that they had to get more oil to the rods so they just got it there full time. It helps, but has its limits. You don’t need a full groove bearing in a chevy? What’s the difference?
Walter P. either came from Pontiac or Buick...I forget which. That’s why the blocks and oiling systems are so similar as to be the same.
Back then, RPM about 6000 was unheard of in mass surface transportation. So, if the engineers fudged on the rule a bit to make machining and production quicker (therefore saving big bucks) they did it. There was literally zero chance of a rod oiling issue at those RPM.
I learned all this in about 1986-1986. I bought a complete W2 engine from a guy who was a Modified Eliminator guy (the best Eliminator NHRA ever had...those were my kind of guys who ran Modified) and quickly grew tired of bracket racing so he sold everything.
It was a T/A block, with a Milodon Super Stock pan (same thing I use in my car today...there isn’t a better set sumo pan out there) and before he sold it to me, he took the pan off and showed me the oiling system. He was shifting at 8500 and he said I won’t sell you this if you don’t promise to NEVER EVER change the oiling system.
He said he paid a hydraulics engineer to correct the system because he got tired of killing rod bearings. And that engineer corrected the oil timing. It had some small flaws which I eventually correct, but it worked.
I ran the engine for most of the year, and then it broke a couple of valve springs so I decided to freshen it up. I wasn’t building my own junk at the time, so I was at the mercy of the local shops.
To a man, every one of them HATED what was done to the oiling system. I said WTF??? We don’t have bearing issues, why screw with it. None of them had a clue and they beat me into changing it.
We also changed lifters because the guy doing the work HATED the Engle lifters I had, and he sold me some junk **** crane lifters.
When it went back together, the lifters were failing constantly, and everyone blamed the new cam (it was the JUNK Crane lifters) and we started killing rod bearings.
The upshot is (BTW that engine had Carillo rods and an 8 bolt crank) we changed the oil timing and it killed the bearings.
My dad had a friend who was a hydraulics engineer and he came by and looked at what we had going on. I told him how the system was, what we changed and what the results were.
First words out of his mouth were “why did you change the oil timing”? And then I realized exactly what happened and knew I should have listened to the guy who PAID to have it fixed.
So I put it back exactly the way it was, and I shifted between 8500-8800 and sometimes 9000 for the rest of my time drag racing and NEVER killed a bearing.
There are many who claim they shift that high, but I doubt them. They either lie or have a junk tach. I know what it takes to actually make power that high, on 340 inches and,oat guys aren’t even close to having the airflow and parts to do it. And they damn sure ain’t doing it with Chrysler oil timing.
If you want me to type out the fix I will. It’s quite simple really.
