Oil Pressure too high? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mikep · 10-17-2002, 10:47 PM

I rebuilt the engine in my truck about 3000 miles ago and recently switched to 20W50 oil from the 10W30 I used for the first 3000 miles for break in. In the motor I have a meeling Hi Volume , Hi Pressure pump and I am running with .0025" bearing clearance. Anyway when the motor is cold the needle is off the gauge. I mean I can't even see the needle at all and when its warm its at the far right of the gauge . Even at idle its between the 3/4 mark and H . This super hi oil pressure isnt really something Ive experienced before. I'm running the super long Fram filter , valvoline 20W 50 and CL77 bearings. I dont leak a drop. Is this going to blow something up or should I just be happy and drive on down the road? Anyone had similar experiences that turnd out sour?

crazy longhorn · 10-17-2002, 11:13 PM

Its hard to say how much pressure you have with the factory guage. I run a Melling 10555 hy vol/hy press pump on my 383. With 2500 mi on a fresh eng, I run 70 psi hot @ 3000 rpms, & run 20/50 castrol. this is measured by an Autometer mechanical guage. From my understanding , you really dont need or want more than 65-70 psi pressure on a sb chev......the old rule of thumb was 10 psi per 1000 rpms,& 6500-7000 is pretty tight on a street /strip engine! I havent had any problems with my setup, but do have a 6 Q truck pan ,& dont buzz the throttle till the oil temp stabilizes. my thoughts are, toss an after market guage on, just to verify the reading on your stocker. .......crazy longhorn

whateva · 10-17-2002, 11:21 PM

Do you guys realize that with that much oil preasure you are probably bypassing your oil filter?

This is not meant to be a slam on you guys, but why do people feel that excessive oil preasure is better. It is not like the average small block is turning 10,000 rpms like a Nascar engine.

First think I would do is get that 20w50 out of there.

Blue_71 · 10-17-2002, 11:26 PM

i dont know whats too high, but i always run 10w40. i build up about 25 lbs cranking it (and its pretty easy to start) and stay about 35-40 running

*racedvl* · 10-17-2002, 11:29 PM

I wish I had oil pressure........

*Zkast* · 10-17-2002, 11:45 PM

There's also the heat factor. I cant remember the exact ratio but I think its this:

For every 10psi of pressure you raise the oil temp by 20 degree's

The bypass valve will sense a difference between the oil pressure in and the oil pressure out and if that difference in pressure is greater than 10-20 psi it will close off the filter and send unfiltered oil into the system. So if you are running 20w-50 with a system producing 80psi on cold starts, your definatly bypassing the filter. With pressure like that you could easily step down to 10w-30 or 40 and be on the safe side.

mikep · 10-17-2002, 11:58 PM

Bypass? What Bypass ? I'm running the non bypass filter and the non bypass adapter. Full flow all the way! Thats why I am running the tall filter in the first place. It's probably part of the hi oil pressure thingy going on. Iv'e lost more than one engine to having a bypass oil filter. Never again! I probably will go down to 10w 40 or to even 5 W 30 during the cold season.

flyin99 · 10-18-2002, 12:27 AM

I do have a question.........What psi are these factory gauges? I was told by somebody that they were either 40 or 60 psi...if this is so, it wouldn't be that hard to make the needle fly to the other side......................

crazy longhorn · 10-18-2002, 12:50 AM

Im not sure on the 67-72, but 60 psi pins the factory guage on my 78.

72bigblock · 10-18-2002, 02:18 AM

also running that much press. can cause bearing to hyd. lock causeing the bearing to spin. 50 p.s.i is more than you will ever need on the street!

Blazer1970 · 10-18-2002, 08:25 AM

I can't understand why you would want to run 20W50, especially in a tight engine. You are not going to bypass the filter. The bypass valve is only going to open when there is excessive pressure drop ACROSS THE FILTER. This happens when the filter is plugged, not just because your oil pressure is high. When the oil pressure is high, unless the filter is plugged, it is high on both the inlet and the outlet of the filter. The biggest problem with that high pressure is the wear on the distibutor drive gear, and the gear on the cam that drives it. Also, it uses a lot of hp just to drive the oil pump.

crazy longhorn · 10-18-2002, 09:37 AM

I agree that it takes more hp to run a big pump, & dist gear wear is also a concern. I have run a Z28 pump, or a properly clearanced stocker,with a Z28 spring on just about every sb I have built, &had no problems. From the factory ,GM put the high pressure pump on the z28's, & they ran @ 65 psi hot runnin down the hyway. My reading in How to Hotrod sb Chevs tells me that the z28 pump is a good street /strip pc with the proper pan. The Melling pump I have on the 383 has a bolt on pickup, pressure balance grooves,& post extended ito the cover to keep the gears running straight. I probably dont need 70 psi, but from time to time the engine is run up in the 6500 rpm range

slam33 · 10-18-2002, 09:45 AM

Try running 10/40 in it

**Classic Heartbeat** · 10-18-2002, 10:49 AM

I had my 402 rebuilt by a local and reputable engine builder and I wanted them to install a high pressure/high volume oil pump in my engine. They told me that High pressure/High volume oil pumps tend to wash out the bearings leading to premature failure. They also told me that what I wanted was a Low pressure/High volume oil pump so that is what I went with, seeing how they would have to warrantee the engine if it broke. I don't know it to be fact, but it warrents concideration...

WES www.ClassicHeartbeat.com

jhwkns · 10-18-2002, 11:05 AM

I use high volume pumps on any performance small block, and have never had any problems. It gets pretty hot here in Vegas so in the summertime I use 20w50 when things cool off I run 10w40. Pegging the stock gauge isn't a hard thing to do. At 65psi mines buried.

tom hand · 10-18-2002, 05:21 PM

When it comes to oil pressure, more is not better. There is little reason for a street motor to have more than 40 psi. Besides the wear on the distributor gear and the Hp needed to drive it, on most high pressure motors, the rear main seal have a premature demise. My 2 cents.

bigjimzlll · 10-18-2002, 05:26 PM

you know that all sounds right....about too much pressure hurting things....but for me..I vote for the high volume pump with a 7 quart oil pan....better too much oil than not enuff

Blazer1970 · 10-18-2002, 05:49 PM

A high volume pump is fine. You don't need it on a tight engine, but it won't hurt anything. It is the high pressure pump that you don't really want. Most of the pumps come with two springs for the relief valve, so you can choose to install the high pressure spring, or the low pressure one.

6869704X4 · 10-20-2002, 10:33 AM

Check out this site. Good info.
http://www.melling.com/support/bulletins/default.asp

10-17-2002, 10:47 PM	#1
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Oil Pressure too high? I rebuilt the engine in my truck about 3000 miles ago and recently switched to 20W50 oil from the 10W30 I used for the first 3000 miles for break in. In the motor I have a meeling Hi Volume , Hi Pressure pump and I am running with .0025" bearing clearance. Anyway when the motor is cold the needle is off the gauge. I mean I can't even see the needle at all and when its warm its at the far right of the gauge . Even at idle its between the 3/4 mark and H . This super hi oil pressure isnt really something Ive experienced before. I'm running the super long Fram filter , valvoline 20W 50 and CL77 bearings. I dont leak a drop. Is this going to blow something up or should I just be happy and drive on down the road? Anyone had similar experiences that turnd out sour? __________________ No truck :-(

10-17-2002, 11:45 PM	#6
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	There's also the heat factor. I cant remember the exact ratio but I think its this: For every 10psi of pressure you raise the oil temp by 20 degree's The bypass valve will sense a difference between the oil pressure in and the oil pressure out and if that difference in pressure is greater than 10-20 psi it will close off the filter and send unfiltered oil into the system. So if you are running 20w-50 with a system producing 80psi on cold starts, your definatly bypassing the filter. With pressure like that you could easily step down to 10w-30 or 40 and be on the safe side. Last edited by Zkast; 10-17-2002 at 11:50 PM.

10-17-2002, 11:58 PM	#7
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Bypass? What Bypass ? I'm running the non bypass filter and the non bypass adapter. Full flow all the way! Thats why I am running the tall filter in the first place. It's probably part of the hi oil pressure thingy going on. Iv'e lost more than one engine to having a bypass oil filter. Never again! I probably will go down to 10w 40 or to even 5 W 30 during the cold season. __________________ No truck :-( Last edited by mikep; 10-18-2002 at 12:01 AM.

10-18-2002, 08:25 AM	#11
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	I can't understand why you would want to run 20W50, especially in a tight engine. You are not going to bypass the filter. The bypass valve is only going to open when there is excessive pressure drop ACROSS THE FILTER. This happens when the filter is plugged, not just because your oil pressure is high. When the oil pressure is high, unless the filter is plugged, it is high on both the inlet and the outlet of the filter. The biggest problem with that high pressure is the wear on the distibutor drive gear, and the gear on the cam that drives it. Also, it uses a lot of hp just to drive the oil pump. __________________ Tim

10-18-2002, 09:45 AM	#13
slam33 Registered User Join Date: Aug 2001 Location: Long Beach, Ca Posts: 1,432	Try running 10/40 in it __________________ 71 LWB 350/350still working on it but it's going tp be sweet. www.geocities.com/stevemau/slam33page.html " TARGET=_blank>http://www.geocities.com/stevemau/slam33page.html?1004806705410 </A>

10-17-2002, 11:13 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Its hard to say how much pressure you have with the factory guage. I run a Melling 10555 hy vol/hy press pump on my 383. With 2500 mi on a fresh eng, I run 70 psi hot @ 3000 rpms, & run 20/50 castrol. this is measured by an Autometer mechanical guage. From my understanding , you really dont need or want more than 65-70 psi pressure on a sb chev......the old rule of thumb was 10 psi per 1000 rpms,& 6500-7000 is pretty tight on a street /strip engine! I havent had any problems with my setup, but do have a 6 Q truck pan ,& dont buzz the throttle till the oil temp stabilizes. my thoughts are, toss an after market guage on, just to verify the reading on your stocker. .......crazy longhorn

10-17-2002, 11:21 PM	#3
whateva Registered User Join Date: Dec 2001 Location: Poway, Ca Posts: 108	Do you guys realize that with that much oil preasure you are probably bypassing your oil filter? This is not meant to be a slam on you guys, but why do people feel that excessive oil preasure is better. It is not like the average small block is turning 10,000 rpms like a Nascar engine. First think I would do is get that 20w50 out of there.

10-17-2002, 11:29 PM	#5
racedvl Account Suspended Join Date: Jan 2000 Location: Woodstock, IL Posts: 7,020	I wish I had oil pressure........

10-18-2002, 12:27 AM	#8
flyin99 creator of kong Join Date: Mar 2001 Location: Kentucky Posts: 538	I do have a question.........What psi are these factory gauges? I was told by somebody that they were either 40 or 60 psi...if this is so, it wouldn't be that hard to make the needle fly to the other side......................

10-18-2002, 12:50 AM	#9
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Im not sure on the 67-72, but 60 psi pins the factory guage on my 78.

10-18-2002, 02:18 AM	#10
72bigblock Registered User Join Date: Oct 2002 Location: rockford il. Posts: 190	also running that much press. can cause bearing to hyd. lock causeing the bearing to spin. 50 p.s.i is more than you will ever need on the street!

10-18-2002, 09:37 AM	#12
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	I agree that it takes more hp to run a big pump, & dist gear wear is also a concern. I have run a Z28 pump, or a properly clearanced stocker,with a Z28 spring on just about every sb I have built, &had no problems. From the factory ,GM put the high pressure pump on the z28's, & they ran @ 65 psi hot runnin down the hyway. My reading in How to Hotrod sb Chevs tells me that the z28 pump is a good street /strip pc with the proper pan. The Melling pump I have on the 383 has a bolt on pickup, pressure balance grooves,& post extended ito the cover to keep the gears running straight. I probably dont need 70 psi, but from time to time the engine is run up in the 6500 rpm range

10-18-2002, 10:49 AM	#14
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,770	I had my 402 rebuilt by a local and reputable engine builder and I wanted them to install a high pressure/high volume oil pump in my engine. They told me that High pressure/High volume oil pumps tend to wash out the bearings leading to premature failure. They also told me that what I wanted was a Low pressure/High volume oil pump so that is what I went with, seeing how they would have to warrantee the engine if it broke. I don't know it to be fact, but it warrents concideration... WES www.ClassicHeartbeat.com __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys

10-18-2002, 11:05 AM	#15
jhwkns Registered Cruiser Join Date: May 2002 Location: Las Vegas NV Posts: 2,230	I use high volume pumps on any performance small block, and have never had any problems. It gets pretty hot here in Vegas so in the summertime I use 20w50 when things cool off I run 10w40. Pegging the stock gauge isn't a hard thing to do. At 65psi mines buried. __________________ I intend to live forever. So far, so good.

10-18-2002, 05:21 PM	#16
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	When it comes to oil pressure, more is not better. There is little reason for a street motor to have more than 40 psi. Besides the wear on the distributor gear and the Hp needed to drive it, on most high pressure motors, the rear main seal have a premature demise. My 2 cents. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS



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10-18-2002, 05:26 PM	#17
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	you know that all sounds right....about too much pressure hurting things....but for me..I vote for the high volume pump with a 7 quart oil pan....better too much oil than not enuff __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

10-18-2002, 05:49 PM	#18
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	A high volume pump is fine. You don't need it on a tight engine, but it won't hurt anything. It is the high pressure pump that you don't really want. Most of the pumps come with two springs for the relief valve, so you can choose to install the high pressure spring, or the low pressure one. __________________ Tim

10-20-2002, 10:33 AM	#19
6869704X4 Registered User Join Date: Jul 2002 Location: SE NM Posts: 769	Check out this site. Good info. http://www.melling.com/support/bulletins/default.asp __________________ The more I learn about women, the more I love my truck.

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