Oil Pressure

[joea]

I know this has been discussed. I just wanted opinions on my situation. I know the "rule of thumb" 10lbs pressure per 100 RPM.

At cold idle I see 50 lbs
At hot idle I see 12-15lbs (Idle is about 600rpm)
At 2000 RPM Hot I see 40 lbs.

I'm running 20-50 without my oil cooler hooked up. Since this is a fresh rebuild I plan to drop the fluids in 500 miles then hookup the cooler.

My only *slight* worry is the hot idle pressure. According to the rule I'm still ok. I suspect once the oil cooler is hooked up it will help the situation. I don't have the oil temp guage hooked up yet either for the same reason as the cooler. I didn't want to drop the oil to hook them up.

Thoughts?

[DAVID GAGNARD]

Joe;

12 to 15 lbs. seems low to me,so is your 600 rpm idle. Try turning your idle up to around 800 to 900rpms and see what the pressure is,should go up some,say maybe to 20 to 25 and that would be o-k,seems on a "fresh" motor oil pressure should be more than that.....

Cold idle pressure is good and hot at 2000 rpms is o-k but seems a little low,seems you should have at least 50psi at 2000 rpms especially with a fresh motor..........

David

[Roscoe]

I've got 20k on the engine. 70 lbs at start. Operating pressure is 50 lbs. Don't know what the hot idle pressure is offhand. Running 10-30 synthetic.

Roscoe

[joea]

I'll bump the idle up to about 850 and check her blood pressure again. I'll post an update back

[bremillard]

Joe,

You are 15-20 lbs low of optimum. Something may be wrong like excessive clearances or omitted plug of some kind. Your pressure may drop even further when you hook your cooler up as it will blead oil and therefore pressure out of the system. If nothing is wrong you may need a higher pressure pump. The numbers you gave are not alarming but as another poster said, for a new motor they are low. -Bob

[DonC]

Joe:
Don't forget to check the gauge for error.
DonC

[joea]

How do I check the gauge without buying a new one?

[DonC]

Joe:
Check the local yellow pages for someone who sells/repairs various gauges and check with them. You may have to pull it out (mechanical) or take the sending unit to them. If it's electrical you may be able to get the voltage readings of the sending unit from the manufacturer and check it that way.
DonC

[DAVID GAGNARD]

Joe;

I'm sure every engine is different,but this is what I have found with mine concerning idle oil pressures....
For normal everyday use I had my idle rpm set at about 750rpms..... Normal driving,everything fully warmed up idling at 750rpms,oil pressure normally around high 20's to low 30's psi....I also have a warning light hooked up in conjunction with my mechcanical oil pressure gauge,light is set to go on at 20 psi....

When running on the track for the first time after a 10 lap session at 1.3 miles per lap,came of the track and the oil light was on,very scary,looked at the gauge showing just on or under 20 psi.....I revved the motor a little,maybe up to 1200 rpms,light goes off,oil pressure goes up to 35 psi,got in the pits,checked the oil temp,(gauge is under the hood),oil temp on 210..... Next session out oil pressure back to normal,run the session,same things happens.....so now I idle it up to 900 rpms and go out again,after another 10 lap session oil temp holding on 210,oil pressure is 25 psi,light never comes on.....with my motor the 250 rpm idle increase is good for 5 to 8 psi of oil pressure,I have left the idle on 900,would rather have a little more oil pressure than lose a motor,the extra gas it burns is cheap compared to an engine rebuild..........

David

[Rick Parker]

Joe:

There have been many discussions regarding proper oil pressures for all the various engines we use and it is a very opininated subject, with a lot of good information exchanged. Here is my 2 cents worth:

If you are using looser than standard bearing clearances, or have increased the connecting rod side clearances and are using a standard volume oil pump the pressures you describe are probable. The pump DOESN'T create the pressure directly, it only creates the flow/volume of oil available to the system. The bearing clearances and connecting rod side clearances create the path for INTERNAL LEAKAGE which in turn causes pressure to be created because of the restriction. It is the amount of this LEAKAGE that dictates the potential pressure for a given volume. (increase the clearances and the pressure drops) The bypass spring (in the mp or block) sets the maximum pressure that can be reached before bypass ONLY IF there is enough volume/flow available. If you are adding a cooler & related lines you will experience a further drop in pressure unless a HV pump is added. Fluid dynamics will cause the drop.

The 351 Std Windsor pump internals are the same as the HV set used for the 289/302 ie: They move the same amount of oil.

My pressures are as follows with a cooler & -10 hoses.

289 on steroids
Remote Filter & cooler with -10 lines
Melling HV pump with internals coated
80# at cold startup idle (Bypass spring set at 80#)
At operating temp 70# at 3000 RPM cruise and 35-40# at 850-900 RPM idle.
No problems ever with distributor gear. I burnished the cam gear and distributor gear before assembly.
10-40 Kendall GT-1 (Best non foaming oil I have found)

Rick

[clayfoushee]

Joea,

I'm at the the exact same pressures as Rick Parker above on a 427SO (454 stroker), solid lifters, using Valvoline Racing (20w-50) w/ oil cooler and remote filter set-up.

[luke-44]

Joe - one lesson I learned was: A solid lifter cam in a non side oiler block (designed for hydraulic lifters) will have low oil pressure issues, unless the gallerys to the lifters are blocked off. This requires tapping the bottom of the cross gallery to the cam followers and inserting special plugs.

If this is your set up and this is not done, I'll bet this is the problem.

Let me know if you want more info on this.

Bruce

[trularin]

I understand there are "restrictors" that can do what Bruce is describing. Plugs with small holes in them to change the bleeding in the oil system.

I am not completely informed on the Big Blocks, but the 351 Boss/Cleveland has oil bleeding problems that can be fixed with the addition of restrictors. I did this on my block.

First time I used the .060 restrictors. The second time I used the .125 and got the results I wanted.

You may want to look into this, I think Bruce has a point.

BTW, my oil runs about 30 to 40 at idle and over 80 at 3500 plus.

[joea]

I am not running solids...it is a hydraulic cam and lifter setup. I did not have a chance to up the idle on the car yet...hopefully tonight. Thanks for all the thoughts...I'll post back

[joea]

I just raised the idle and brought her out for a run. The idle was actually wanting to stay about 1100rpm when warmed up so I think I went a little too much. I was able to kick it down at a light to about 900. At 900RPM hot it was just below 20lbs. At 1100rpm it was about 20 or a little more. At 2000rpm it was just below 40lbs and at about 2200 she was at 40 even. Most pressure I saw hot was about 45lbs (even at about 5500 RPM).

I have hydraulic lifters, roller rockers and Edelbrock heads. I have not restricted oil to the rockers. It was recommeded that I do this to raise the pressure.

Also I found out my pan has a 9 1/2 qt capacity. I think there is only 9 qts in it (put in by the dyno shop). I think I will drain the oil, install the cooler lines and fill it back up.

What are your thoughts? Should I do something to affect the pressure and if so should I stop running the car immediately until I do so?

[rritchey]

Well, since I built the shortblock, I should chime in..... you guys out there feel free to comment on my comments....

OK, with 55 or 60 psi cold idle there are no missing plugs. If you have them available, go back and look at your dyno sheets to see what the pressure was during the runs. The motor should not have lost very much pressure since its first start. It will loose a tiny bit, due to break-in but not much. If you look at your pressures, they are about 10 to 15 pounds less than what everybody says is "normal", which is what you would gain by adding the restrictors. The Edelbrock heads are worse about bleeding oil pressure than stock heads were - they have a real big passage up to the rockers.

As for the extra 1/2 quart of oil, I wouldn't bother with that. It won't make any difference. The cooler will most likely drop you down another 3 or 4 psi, so you really should look into getting the restrictors installed.

You can do it without removing the heads if you use dowels. You will have to take off the rockers and measure the hole where the oil comes up from the head into the rocker stand. I think I remember you said you bought a micrometer, or maybe it was a dial indicator - anyway, use a good method to measure it because you want the dowel to fit tight but not so tight you have to use a shop hammer to drive it in. Have a local machine shop turn down 2 aluminum dowels that are your measured diameter by about 3/4" long. Then have them drill a .080" diameter hole right down the middle of it. Bring them home and insert them into the holes and re-install the rockers and valve covers. Problem should be solved.

One thing about your engine - since it has LeMans rods, the rod side clearance is high. They are old rods, been around the crank a few times, therefore the side clearance is not as tight as it used to be. Don't get me wrong, they are good rods - yours were re-sized, re-bushed, beamed, peened, polished, new bolts, new dowels.... they are not going to cause you any problems other than the inherent loose side clearances. I would install the restrictors, use straight 30wt or 40wt oil and drive it. Just for kicks, you could get it warmed up, take the distributor out and one or both valve covers off, and spin the pump with a drill. I think you will be shocked at how much oil is being pumped up there. Be careful though, you can make a mess real quick by overflowing the heads and coating your headers - and smoking up the neighborhood next time you fire it!

Thank you and have a blessed day!

Randy Ritchey, P.E.
1834 W. Arrowhead St.
Fayetteville, AR 72701
479-527-9166 office
479-841-7142 mobile
rritchey@cox-internet.com

[joea]

interesting...http://www.clubhotrod.com/t229.html

[joea]

Sorry I haven't updated you sooner. I did finally get around to dropping the oil, hooking up the oil cooler lines, and taking her for a spin. Guess what happened....most people thought the oil pressure would have dropped a bit further by adding the cooler. Well, I'll keep you in suspense a bit longer as I explain another bit of info. When I brought the engine to the dyno for the initial cam break-in, I sent it down there with a NAPA gold (ie WIX) filter. After the break i they changed the oil and put on a Fram, which I left on there until the first oil change at about 500 miles or so. I figured the Wix filter would give me a few extra PSI and was hoping it might offset any loss I was expecting from the hooking up the cooler. Just to remind you my cold start oil pressure at idle was 55 psi. After hooking up the oil cooler, and putting a NAPA gold (WIX) filter on I started her up. Guess what the gauge read? 70 psi! Thank you Santa for the Wix filter! I'm still shocked that it made that much difference. After letting her warm up I would normally see an average cruise oil pressure of about 40 psi. I was seeing an average of 55 psi after the filter change and adding the cooler.

[Bob In Ct]

Joe:
I know it's a dumb question, but I have to ask it. Is the oil pressure sensor in front of or after the filter and cooler?

If it's in front of the filter and cooler a more restrictive cooler and/or filter will raise your oil pressure reading.

Bob

[joea]

The sensor is at the top of the filter adapter. The oil cooler lines are hooked to a sandwich adapter between the filter adapter and the filter. I guess that would be in front? Are you saying it is a false pressure reading or the cooler adapter helped increase the pressure?