When is too much oil pressure, too much? [Archive] - Chevelle Tech

: When is too much oil pressure, too much?


Dave
May 23rd, 07, 1:31 AM
So, now that I'm really starting to put the miles on the motor, I'm noticing that I think the oil pressure is too much. Even when it's up to temp, cruising down the freeway at 70MPH, I've still got 75#'s oil pressure. Heck, just idling at temp it's still around 40#'s.

I originally had a Melling HV 55, but my builder said it was too much, and used a stock type pump. I think the pump/oil pressure is to blame for my leaky motor.

I don't know, is it too much pressure?

nakamura_racing_sports
May 23rd, 07, 4:34 AM
If you don't ever see over 100, I think it's ok. I know a few racers that see a bit over a 100 with no problems. 70 at idle would be too much though. Cold idle, I have 40, 30 at hot idle. Mine is a HV pump though. Didn't really make a difference when I switched from the Z28 pump. I think the number was M55A or something like that.

FTG53
May 23rd, 07, 9:04 AM
Dave
Our small block can run up to 80+ psi cold and 60psi to 70 running at speed, 30 psi hot idle. We do use the HP4 Filter to avoid leakage at the filter gasket during cold starts. The pump is the Melling HV. No other leaks for the past 8 years.
My question is where is the engne leaking from? VC gaskets? Pan? Intake? You may want to look at the pcv system and see if you are building crankcase pressure. Excess crankcase pressure will cause some leaks.
Is it a fresh engine? If so, some of the bolts may need to be re-tightened from heat cycling.
Just some thoughts, Hope this helps.
Frank G.

charbilly2001
May 23rd, 07, 2:05 PM
If you don't ever see over 100, I think it's ok. I know a few racers that see a bit over a 100 with no problems. 70 at idle would be too much though. Cold idle, I have 40, 30 at hot idle. Mine is a HV pump though. Didn't really make a difference when I switched from the Z28 pump. I think the number was M55A or something like that.

Anything over #100 is BAD for "babbitted" bearings. (That grey stuff on the bearings that you can scratch with a finger nail.) If you really have to have that much pressure you should run aluminum faced bearings.

That said, its been my experience over the years that any SBC will live nicely at unreal RPM with oil pressure at #40 lbs for drag racing purposes especially if you have a baffled pan to control oil movement. Likewise when on circle tracks oil pan baffling is critical.


The issue with "babbitted" bearings is that ultra high oil pressure will "shear" the babbit off and increase your bearing/crankshaft clearance. Not desirable.
:)

Tom Mobley
May 23rd, 07, 2:55 PM
sounds like the builder forget to get rid of the HV pump to me.

busterwivell
May 23rd, 07, 3:00 PM
My understanding is a high volume pump just moves the oil faster? A high pressure pump is what is causing your higher than normal readings. I've got High volume pumps in mine, but the "pressure" seems to read normal.

Dave
May 23rd, 07, 8:54 PM
The leaks are actually minimal, just a small drip out of the main seal, and a little seepage on the oil filter. I just don't like oil leaks.:noway:

The Builder didn't forget to leave the pump out, I brought the Melling, and He didn't want it, so I sent it back to Summit. He got one to install, if I remember correctly, it's a stock type unit. I'm gonna have to try and get ahold of him to find out.:confused:

I'm just curious as to if that much pressure is a bad thing? I know that if I was trying to wring every last pony outta her, it wouldn't be, but as it stand's, I shouldn't have to worry about getting oil to the motor.:D

I guess one thing I wonder about is, with the hydraulic lifter issue that I had, switching from the Crane anti-pump ups, to the Comp 812's (Stanadyne,I believe) made a huge difference in the noise of the valvetrain. Now, I'm wondering if the excessive oil pressure is not allowing my lifter's to have a little give? Hence, some of the sewing machine sound.

Tom Mobley
May 23rd, 07, 9:35 PM
anti-pumpup lifters are expected to be noisy as the have a looser fit on the internal piston. These lifters don't actually prevent pump-up, but allow it to bleed off much faster resulting in quicker recovery from the pump-up situation.

excessive oil pressure is not somehow "better" than normal oil pressure in any way and can cause issues not found in engines with normal oil pressure.

any chance you've got an electric gauge with the wrong sender? there's senders for 60lb and senders for 80lb gauges, they're not interchangeable.

Dave
May 23rd, 07, 10:02 PM
Mechanical gauge. I'm pretty sure it's correct, as when I adjusted the lifter's while running, it had alotta pressure.

Dave
May 24th, 07, 8:46 PM
So, Anybody got any solid opinion's on this? I'm kinda thinking bout pulling the motor, bumping the cam, and maybe changing the oil pump?

Keith Tedford
May 24th, 07, 9:56 PM
From my experience the L78 and L72 engines work fine with the stock setup. Most died from dropped valves, not from lubrication problems. Our L72 had close to 200K miles on it and saw 7200 on occasion. No problems. We've put abut 30K on our L78 car and about 15K on a previous L78 car. No problems either. With Chevies, more is not better for the most part. Excessive oil pressure just eats up horsepower that we try so hard to gain in the first place. Advertising does sell a lot of aftermarket stuff though.