I cannot answer that but Sanborn was using pushrod oil and he had bushed lifters with a very small feed hole.
Ok, then what he did makes sense. He HAD to have some oil on the drivers side. I’m still not sure about needing the feed up at number 1 but I will say it didn’t evidently hurt anything.
I know when I get the mains from the OE feeds and the feeds through the cap we could never get steady oil pressure on the dyno. I wasn’t data logging at the time, but on the dyno you can monitor it.
It was about a 16-18 lb swing, and the funny thing was at lower RPM (IIRC this was a long time ago and what notes I took are either gone or went with some part of the engine when I sold it) the pressure was pretty steady. Once you got up to 6500ish it got worse and again IIRC anything over 7500 the swings were pretty significant. And the higher the RPM went, the quicker the pressure moved. There was a ton of discussion about whether the sensor/computer was monitoring the pressure at a high enough rate, so we got on the phone and made some calls and were told it’s plenty fast to keep up with that.
Again, the oil pressure gauge was way too slow to respond to catch it. When we first looked at it, the dyno guy said WTF is wrong with this thing. I said I have no idea. First I’ve seen of this crap.
I lived with it because I had no idea what was going on, and neither did anyone else. AFAIK, I was the only one using that system, but I suspect the Modifed and Super Stock guys were doing it or similar. Anyone I got on the phone was tight lipped like a crooked politician.
When I finally put the system back the way it was when I bought the thing, the oil pressure quit doing it. Even up to 9000 on a couple of hero pulls on the dyno. Even with 110 psi at that RPM.
So the inference that I made (because that’s all I have as I have yet to find anyone who can say otherwise) is that the oil pressure coming in from the caps was at least 20 psi higher than the oil coming down from the passenger side oil gallery. It could be a greater pressure drop than that, but I know we had 110 psi at 9k to the bearings (or damn close to it because I pulled the pressure from the line at the pan that fed the number 3 main) and those feeds had much less distance to travel to the bearings and quite a few less 90 corners to travel.
My assumption is at that point, it was easier for the oil coming in from the cap to back feed into the OE oil passages because of the pressure differences.