full groove main bearings oil pressure ?

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I get you, but without the rotation (movement), there's no oil wedge. I didnt think boundary layer by definition has movement as a priority and in the case of automotive bearings it has to be. I think you're looking at the foundation of a house and I'm looking more at the framed and sided version...lol.
 
when I was racing stockers we found every engine with fully grooved mains had this issue. we found it to be from full oiling to the rocker shafts also we restricted flow to the shafts because it filled the vc and wouldn't drain back down (always turning left)so the pump would go dry after 10 laps.
 
Now your last paragraph on opening up the oil holes and the bearings being able to handle the extra flow is diving way too deep. The oil flow for the main, rod, and cam bearings is limited by the radial clearance. If you increase your radial clearance to try to get more oil flow through, the clearances will be too great. The engine will knock due to the excessive clearances and you will wipe out your bearings and mating components

I never said anything about " If you increase your radial clearance to try to get more oil flow through" I was talking about cleaning casting flash out of the cast in oil passages! The bearing clearance provides a "calibrated leak" if it is to large you will not have good oil pressure. Yes you can have excessive oil to the valve train.
 
I run full groove mains in my 440, all clearances at factory specs.
use 15/40 mobile 1 with hy volume pump the pressure is off the scale cold and 65 psi at hot idle with 8 quart capacity.
I run standard mains in my 383, all clearances factory spec, stock pump with high pressure spring 20/50 vr1 provides 80 psi cold 50 psi hot at idle
 
Same here running full groove on mains std pump with heavier spring,Mopar harden shaft 15-40wt oil, cold 75psi, hot 25 idle ,2500-3000 75psi (318 teen).
 
Assuming main bearing clearance is the same, full groove mains should make NO difference in oil pressure. If they do, it's likely because your rod bearing clearance is excessive. And the half grooves were starving the rods half the time.

Do your rod bearing have an oil spray notch?
 
My last 440 had full grooved mains. It had 15-20 hot idle and 60psi at 5700 RPm with 20/50 oil
 
"I never said anything about " If you increase your radial clearance to try to get more oil flow through" I was talking about cleaning casting flash out of the cast in oil passages! The bearing clearance provides a "calibrated leak" if it is to large you will not have good oil pressure."

Couple things that you might want to research further - first I'm not aware of any "cast in" oil passages. All are drilled so no casting flash. The flash removal is to encourage faster return to the sump because there is significant flashing in the valley, enough in some cases to completely fill what should be cast-in drain back holes. I always deburr the valley and in the past if needed I'll add drainback holes next to the lifter bores and shape/debur them. Second - When we talk about enlarging the passages - we're talking about the passages that go from the right hand lifter galley down to the main bearing bores. There's one for each main saddle, and the ID can vary year to year. I drill all of them to 5/16" mainly because that was the long bit I was able to get my hands on years ago. 9/32s is also popular.
 
There's no use having a high volume oil pump without the increased capacity of the pan.
If you had a high volume oil pump with say a 4 quart pan, you could easily suck the pan dry if you were doing a high R.P.M. charge for a prolonged period of time.
I lost a couple of rod bearings back in the day while i was top ending the 383 in my '69 Super Bee because of this. It had a stock 383 and a 4 quart pan off of a Newport in it.
Volume versus drain back should go hand in hand as well as considering the capacity.
High capacity pans and windage trays were put on all of the high performance and severe duty engines back in the day for a reason. (Industrial and motor home)
When i built the 440 for it, it got the 6 quart pan and Hemi pickup with a high volume and high pressure spring oil pump with the windage tray. The bearings were set at .002 with fully grooved mains and regular Clevite 77 rod bearings, and the pressure was 60 psi cold and 40 psi hot at idle with a max of 70 psi at 6,000 rpm using 10w 30 oil. I had no problems with it and i drove it for 10 years and raced it a lot. The engine was getting kinda tired by then, but the oiling system never changed.
These days, adding synthetic oil to the mix makes it even better.
 
moper said:
Here's a very good article:
The Lubrication of Bearings — Principles of the Oil Film and Wedge | NZETC

I think you might be confused about boundary layer lubrication... Internal combustion engines use hydrodynamic lubrication because the oil is the load bearing member and the development of the oil wedge is dependant on the rotational motion. With boundary layer the surfaces are the load bearing members. Least that's how I understand it.
Also in regard to having high indicated pressures... The oil pressure tap is off the lifter galley in smallblock Mopars. If you are pumping a ton of oil into the system, you are not reading what the mains are seeing. You're reading what the lifters are seeing and hoping that this indicates the mains and rods are getting enough. If the passages to the mains are left at factory size, you are not "seeing" the bearing clearance in that reading because you're pumping so much oil into the galley. Pressure is resistance to flow and what it indicates can be doublesided. You have to make sure that the higher indicated pressure isn't resistance caused by passages that are too small or too much of a volume entering the system. Otherwiase you're using a bit of power to make a bunch of heat.
Click to expand...
Pressure is pressure no matter where it is read.
 
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