BLKWS.6

what parts determine oil pressure. I know mains and lifters do, but what really influences oil pressure? IE, if my motor had 300K miles on it and idled at 20psi, what is it that would have worn to cause the pressure loss?

I guess I never understood engine oiling well. I viewed it kinda like a BIG mechanical bug with the blood just pumped around all over EVERYTHING in it. Anyone have any diagrams of LS1 oil paths?

Just curious

Quickin

I think the main bearings and there functionality mainly determine oil pressure.


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fatjet00

From what I understand, oil pressure is determined by the clearences on the main, rod, and cam bearings. You can gain more pressure by swapping different springs in the oil pump. The reason newer engines have more oil pressure than one with 250,000 miles is all the above clearences are tighter.

BLKWS.6

SO the conditions of the bearings in a motor are indicated by oil pressure (roughly, and I know its not a hard fast rule)?

Slow00ls1T/a

that sounds about right
i dropped 20 lbs of oil pressure then 5 days later it started knocking real bad like a spun bearing

GuitsBoy

iTrader: (4)

yeah, when bearings start to wear, more oil flows out through the gap and its harder to maintain a consistant cushion of oil. All the oil is bumping into the pan instead of staying in a mostly sealed system, hence the lack of pressure.

That being said, our motors, especially teh early years, had a problem with the pressure releif valve sticking open and bypassing all teh oil instead of routing it through the block. You need a pressure releif valve when youre at WOT and the pump is trying to flow too much oil through the block. However if the valve sticks open and you return to idle, your just dumping the oil back into the pan and none of it is going to the bearings anymore.

BLKWS.6

I am still confused as to how its a closed system and thats why I wanted diagrams. I just dont see how oil pressure is built, I have had the valve covers off my 5.0 and the engine running and the oil ran out of the pushrods/over the rockers, if it was really 40psi closed system it should have HOSED me/engine bay/neighborhood. I am confused still as to the path the oil takes.

GuitsBoy

iTrader: (4)

Oil goes:

Oil pan > Pickup tube > oil pump > mains gallery > main bearings > through the crank bob weight holes > rod bearings > drains back to the pan

From teh oil pump, its also split to the lifter galley > fills the lifters > up the pushrods > through the rockers > onto the springs > drains back to the pan.

Picture the oil system like a garden hose with a nozzle on the end. Open it up half way and some water will drain out the end (bearings edges and pushrods/rockers) but the pressure inside the hose is still pretty high.

pHEnomIC

iTrader: (14)

So when an engine is off, most of the oil drains back into the pan eventually, so every time you start it up, internals are mostly dry and it takes a while for everything to get coated?

Just want to verify something.

GuitsBoy

iTrader: (4)

I wouldnt say its dry, as nothing that touches oil is easily dried, but technically yes. It does take a short while to pump up. As long as the pump is primed, it should be pretty instant though. After an oil change, especially if you dont fill teh filter, it could take a little longer. Maybe a second or two.

Quickin

Its not a closed system. Oil suirts everywhere right into spaces inside the engine that are just big air spaces, like if oil was squirting out of your bed in your bedroom. If the oil gets through the worn oil holes in the main and rod bearings, it flows better, giving you less pressure. If the velocity of a fluid increases, its internal pressure decreases (Bernouli's Principle). So if the engine is new and tight and nothing is worn, the oil is actually slowed down and pressure is higher.

I had no clue how oil traveled through an engine until just about 4-5 months ago, and I had no clue that a main bearing is not a bearing as most people know bearings. Check out an engine in peices and you'll get it.


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BigDaddyBry

iTrader: (15)

And come to think all this time I thought PV=nRT....PV=T....P=T/V

Damn gas.

BLKWS.6

GET THAT OFF MY SCREEN! I studied like a bitch to just pass that test a few weeks ago

I have seen a main bearing, and thats why I DONT UNDERSTAND oil pressure. All it is is a flat, curved strip of soft metal that the crank glides on with a coat of oil in between. How is there oil pressue? Sorry, im dense

What do LS1's run oil-pressure wise with 0 miles? Anyone remember? (hot idle)

Quickin

If the smooth flat, curved strip of soft metal has grooves (scoring) in it from bad oiling the oil will squirt out onto it from the crankshaft and escape back into the oil pan more easily. That will be a decrease in the pressure reading. You need to look at a crankshaft and you'll see the little holes where the oil squirts onto the bearing from the crankshaft.
If you lose a bearing than you'll see how oil pressure will literally crash to nothing, because the oil will free-flow too much. Pressure happens when the oil backs up in the system as its squirted onto the bearings.

About 42 psi is good for a new engine or a very old engine in good condition. I still have 41-42 psi all the time and its a 4 year old stroker engine. I think it does about 36-38 at idle after warmed up.


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