>>>*The real magic of oil is that it doesn't want to move.

To even get it to move at all, we have to keep it under pressure.

*Since it doesn't want to move, the molecules, being very slippery because they roll, stay where they are forced to be very well, and they also resist crushing force.

This means a soft piece of metal (bearing) can slide up and over a hard piece of metal (Crankshaft) and never touch, even though the oil film thickness may be measured in the millionths of an inch.

When an engine is running, the oil gets whipped, the sump is full of air. 90% air, about 10% oil.

This is enough. It doesn't take a lot of oil to get the job done. But when the situation becomes no oil, failure is in seconds.

There is a post regards inclines, etc. No problem for folks running dual transfer cases, RPM is up a bit, oil fills with air, the pickup is covered.

It isn't the speed that gets you, it is idling, air bubbles burst, oil settles in the sump, the pickup will draw air first if it can.

Bearings can heat up and score in a very short time....*EB

Gravitation + cavitation = frustration <img src="/forums/images/graemlins/cheers.gif" alt="" />

Edited for Hiker, okay then = damnation <img src="/forums/images/graemlins/pfft.gif" alt="" />

Ode to Darin-- GRIPTION ROCKS <img src="/forums/images/graemlins/kewl.gif" alt="" />

oooooooookay

Ted, please expound on excessive pressurization as well... I have seen dry sumps with too many "washers" go tits up due to bearing wash. Just finishing a small block chebby (my own) rebuild due to excessive oil pressure...

Mike

>>>*K....The number one problem we ran into with too much pressure was heat. Normally with a dry sump this isn't a real concern because of the volume of oil. Those usually heat up because of too many bends in the plumbing, so we always did everything we could to keep the lines as straight as possible. The key seems to be 10 lbs of pressure per 1000 RPM, more is a waste of energy.

*Plus with poor plumbing (all those spiffy blue and bronze couplings all over the place that look cool) each bend reduces pressure, so it is possible to read 80 lbs on a gauge and have no pressure at all at the end of the system.

We had one tour engine we used a pressure gauge on each end of the motor. They read 80# at the rear one and 35# at the front one, just right. *Used to watch the front gauge drop to 10# in a tight turn as we just came back on the throttle. That made us nervous at first but we soon realized it was normal and plenty of pressure. Nice part of that was if suddenly the front gauge dropped way low, we knew something was going to he** in the $25,000 engine and could shut her down before the big cloud of smoke. Another odd thing we noticed was when the engine read 40# at low speeds on the rear gauge, the front one only dropped to about 25#. This told us there is lots of restrictions in the system from front to rear, even increasing line pressure by 40# only gained us 10# at the end of the line.

The bypass can be set to trip at around 75# which is enough for nearly any application. The mistake comes when the system can reach bypass with lots to spare, up goes the temp. Overheated oil does not lube well, the molecules get so excited they head off in all directions instead of staying where we want them, yep, bearings go byebye.

I have heard and read reports of excess pressure "eroding" the bearings, I can't say I have ever seen a case of that for sure. My own feelings are that instead the oil film breaks down due to the buildup of heat allowing metal to metal contact which fails the bearing.

One fast way to see what happens is heat a cast iron frying pan to nice cherry color. Then pour a few drops of good old 10W-40W in the pan. (Stay out of the way if you try this..)...*LOL**..It will kinda go "YIKES!" and bounce around all over the place. We know that the oil wedge on a rod bearing under race conditions will see 600 degrees plus right at the point of load normally, and 350 plus in a little 22RE just going up a hill. Ever notice that after a hard race, the oil temp and coolant temp will begin to climb AFTER the engine is shut down? This is because the oil in the sump begins to collect the heat from the oil that was in areas running much warmer.

Volume and coolant temperature is all that keeps the oil temperature down, this is why oil pans are thin, to help radiate heat. Dry sumps have less problems with heat soak but still do to some extent.

Back to the excess pressure concerns, I know of just one case that was a maybe from erosion. This was a 4.3L GM V-6. The builder wanted "good" oil pressure so he used an HV oil pump with the heavy spring. Combined with very snug clearences and rear oil galley restricters (mechanical cam) it pegged the gauge at hot idle. No oil filter, just a plate and a reroute line, think he would have blown any filter made off the thing at startup. Worse he ran 50W racing oil for "good" film strength.

It made it 4 warmup laps and 3 laps of the first heat race and locked up, this on a little 1/4 mile short track.

*Lots of damage at teardown, but I found one main and a couple of rod bearings that had what looked like polished grooves right in the center of the bearing shell. The center part of the crankpin was clean and shiny, damage everywhere else. So maybe on that one bearing surface erosion actually happened.

I saw another funny case of what oil does once. This was a 2300 Pinto NASCAR Hobby stock class engine, (same class that the 22R can run in now...fun stuff!) Anyway, this one ate camshafts. The only change we made was to get around the hydraulic rule by plugging the lash adjusters with an aluminum plug and resetting the tops back on. (You didn't hear that one from me...*LOL**). To make sure of good top end oil we bypassed the hollow camshaft and mounted spraybars off a 2000CC Ford engine.

Mistake. I thought it was the lash adjusters, switched back to stock ones, it ate the camshaft again. I finally figured out that the wind tunnel off the cam lobe at 7500 RPM was enough to make the oil spray just spin alongside the camshaft and never get on it. A certain national class Nissan racing team had a similar problem, I ran into their crew chief in the grandstands at the Portland Speedway. We had gone back to hollow cams, solved our problem. I mentioned it and his eyes lit up, that team won a lot of races after that.

Oil does funny stuff....

I say heat from hydraulics is the biggest problem, though...*EB

Cool, thanks for the education and what to look for in the future.

Mike

Hey EB,

I know a little off topic, but what's your general feeling on synthetic oil nowadays?

Not trying to steal the microphone from EB, but I have lots of experience with SYN lubes.....Overall, they are better.

The thing to remember with SYN oils is they are designed/formulated/constructed to do what fossil based oil is "adapted" to do....And that SYN oils do it better and longer.

Lubricating oil has a big job. It has to prevent metal-to-metal contact between parts that are subjected to violent forces and also carry heat away from those parts. And while it's doing all this, it can't suffer or breakdown under those conditions. SYN oils are better at this than fossil oils.

Proper lubrication is achieved by not just the selection of oils used, but also by design of the components you need to lubricate.....cranks/rods with larger bearing surfaces offer a larger area for oils to work, but they also must be clearanced properly to allow sufficient oil flow......flow carries fresh oil thru the bearing and removes heat.

Race engine builders learned long ago to open up bearing clearances to allow more flow. They also learned to increase journal diameters and campher/polish surfaces....Increased clearances allow more flow, canphered/pollished surfaces offer less restriction to flow.....larger bearing surfaces spread the force out reducing the chance that forces will overcome oil film strength......But in order to support larger bearings and bigger clearances, then you had to pump more oil-flow more oil.....

That's when they developed High Volume oil pumps.

That said, then installing a High Volume pump on a stock clearanced engine only caused higher oil pressure, not better lubrication....And the possibility of flow induced bearing errosion became a worry.

Pressure urges flow, and flow insures fresh oil to carry away heat, but flow only happens if clearances allow it, right?

So that said, then you can follow that proper lubrication is a balance of many things....It depends not just on pressure, but also flow. It needs to be balanced and controlled so that all bearings get enuff oil to not just keep a film, but to also not overheat....Syn oils do all this better than any fossil oils can ever hope to....But the engine builder has to help by designing the engine to allow sufficient oil flow at every place in the oil path.

The lube engine designer is restricted in his efforts by several brick walls....First is the temp extreems the engine will face in normal use-from Alaska to Vegas. Then there is actual engine design....the path the oil must take from the sump all the way thru the engine and back to the sump. He has to calculate the requirements of each friction surface and work with other designers in a balancing act....Most engines send oil first to the crank and rod bearings, then port that same oil to the cam and finally the heads and rockers.....as that oil flows along that path it picks up heat and gets beat pretty hard....by the time it reaches the cam/lifters, it has already done a hard job and it is there where it experiences the final torture.

On many engines, the cam/lifters/followers attempt metal-to-metal contact like no other place in the engine....add to that the tremdous heat produced by the head from the passage of cumbustion gasses thru the ports and the fact that this oil is farthest from the pump and at it's least level of pressure/flow, then you can understand that this is where most oils lose the battle and break down....SYN oils resist that breakdown best in this area....this is where they shine.....This is where they win over fossil oils.

EB- If the sump has 90% air in it when the engine is running then what is the oil pressure gauge reading? Scary to think your pickup/oil pump is sucking foam.

>>>*Used to scare me, too, especially since I knew it was doing that even early on when we were drag racing. Then one day I was down at Kay Sissel's shop in El Monte, got invited over to Moon Equipment's dyno shop to see some neat stuff. (I was a mid-20's kid and it was like a candy store in there..)

They had an engine with a clear oil pan they were testing, I stood there and watched the oil "float" alongside the crankshaft which looked like it was just sitting there wrapped in oil. Every once in awhile, the oil would go WHOP! and fly all over, the whole process would start over.

It would then get hard to see, soon it would clear up and all that would start all over again. Once the oil got really hot we couldn't see in there anymore, it looked like it was spraying all over the place.
Interesting stuff, I learned a lot that day back in February 1969.....*EB