Rich, OEM's have gone to gerotor oil pumps which now allow for more oil pressure with less parasitic loss. Pressure is my friend. Oil pressure = long engine life.

Karl

What happens to hydrolic lifters as pressure is increased/decreased? I know that the intention of the hydrolic lifter is to allow lower valve lift at low RPM's to promote better intake air charge(which increases fuel economy). But at what "pressure" does the lifter appear solid?

I just replaced my 60V6 pump with the HV pump a couple of years ago. The stock gauge indicates 60+ psi at 3k+. Seems to be a little high, so maybe I'll try a thinner oil (5W-30 stock).

What hydraulic lifters have you been using? They don't allow lower valve lift, they allow for adjustments in valve lash so there is none. You can be limited by valve lift, but they don't adjusted to allow lower lift. The only ones I can think of are those special hydraulic lifters that do that, but I didn't think they made those anymore.

I've never quite understood how they work. To adjust them, valve is closed, lifter down off lobe, and then tighten to 0-lash and go 1.5 turns past. This compresses the spring in the lifter. So do the lifters not have enough pressure to "pump up" and stop the valve from seating?

Not from what I know, but some of the guys on here may know different.

All the hydraulic lift is suppose to do is take up any slack that is between the pushrod and the rocker, when adjusted correctly.

Thanks for the writeup Rich. Makes the subject very clear.

What do you consider "tight" bearing clearance, and what is "loose"?

Typical is between 0.025-0.030". Over 30 is "loose".

Rich

don't know about v-6's but chevy v-8's only need 2psi of oil pressure to keep from doing any damage a friend of mine had 60+psi and blew out the o-ring on his oil cooler four times and broke the adapter plate that the filter screws on to before finding that was alittle high for his needs you might want 5w20

damn, I'd think that a tenth of those numbers would be closer...

Somewhere I was told 1.5 to 2 thousandths per inch of shaft size. Or at least that is what is stuck in my mind?

So, I left out a zero!!!

0.0025-.0030"

Doh.

Rich

I think "film strength" is the property of the oil that allows the bearings to operate without melting down. The oil flow helps pull the heat out of the area too so you don't overheat the oil film and crap out on film strength. By definition film strength is the amount of pressure needed to cause metal to metal contact by displacing the oil film. Bad when that happens in your engine. Knock knock knock........

The synthetics totally kick *** on the dinosaur oils in this area, 2 to 3 times higher film strength ratings if I remember right. Get some main bearing bores out of wack just enough or lose oil pressure for a split second and if you're lucky the film strength of the synthetics might keep you from melting it down. On an engine I'm beating I wouldn't run anything else after break in. You can easily double the oil change interval to cut the cost difference. Running good quality filters like the Purolator Pure One or a synthetic media filter changed every 3K is cheap insurance on keeping the oil clean. I have a buddy that ran Mobil1 synthetic in his Honda Accord from day one when new. Changed it every 10K miles and filter about every 5K. Engine was clean as a pin inside with great compression when he crashed it at about 200,000 miles. Good stuff, just won't sludge up on you.

On the higher pressure part, I work on hydraulics a lot. Our positive displacement pumps draw more amperage when you crank the regulator up for higher system pressure. You can hear the pitch of the pump change as the output pressure is dialed up too. I believe they are doing more work as more energy is being expended to drive the pump ( higher measured amperage). I'm thinking that a high pressure relief spring is a good idea but it does increase HP loss through the oil pump. Very reasonable trade off if true.

Good thread, Michael

very very true.

You also mentioned oil flow for cooling and that's worth talking about. The only way to increase flow in the engine oil circuit is to have the oil pump make more pressure, (or increase the bearing clearance). And a HV pump won't flow more oil than a Standard Volume pump when on the relief circuit. A HV pump at 40psig relief is going to flow, (through the engine oil gallies) exactly the same oil as a SV pump at 40psig relief. Pressure is the only way to increase system flow at that point. Thus the importance of oil pressure.

HV pumps give a bit more low rpm (idle) flow and pressure, though, than SV pumps because of the taller gears. That's why they are so popular. Race cars don't need HV pumps because they don't idle at low rpm (650 to 850rpm). Keep that in mind when comparing what a race car uses to what a street/strip car uses.

So that is why the 70 psig high pressure relief oil pump is so popular, (SV or HV). If the motor turns to 7000rpm then you'd think the oil system should peak at 70 psig to give more flow to the bearings. I agree.

Yea I've heard that NASCAR dry sump (gerotor) engines run 45psig and that may be true. If it is true then how do they get away with it running 9000rpm? Very interesting.

Karl Ellwein