OK, so in the motor is a melling select high volume (10% over) pump, oil cooler, canton pan and accusump and I used havoline 10-30 for break in. Motor fires up and sounds great. Heres the problem. on start up the oil pressure was about 45-50 psi and stayed there for the next 5-8 min with water temps rising and oil temp not yet registered on a gauge that starts at ~140. Then over the next ten minutes the oil temp and oil pressure gauges seemed to be connected, oil temp up and pressure down until oil temp stabilized at ~220 and oil pressure at 25!!!. Water stable at 210. Over the next ten minutes everything was perfectly stable and the motor continued to pur. No oil leaks and not even a check engine light. Oil pressure verified on the accusump gauge, and the motor was completely preoiled using the accusump for its first start. Im hoping to God I just need thicker oil but even the factory motor runs about 40 psi on 5-30. The only thing I can think of is I used clevite H series 1/2 groove bearings that I have heard some say can lower your oil presssure but others say they wont. If the bearings arent out of it (no sparklies on the dipstick so far - will drain the pan soon) then what else could it be? I cant imagine its a bearing clearance prob, everything was machined and went together well. Im hoping since the oil pressure was stable before and after the oil heated up, its a viscosity/crappy oil problem. Thoughts? Please tell me to put some good 15-50 in it and it will be fine....

 

Most likely bearing clearances. What are they on the mains and rods?

 

mains are standard and rods are only 10 under-

 

are you running 5 quarts?

I'd assume with an oil cooler, you would need a little more, maybe 1/2-3/4 of a quart more to compensate for whats in the cooler and lines at a given time.

Maybe? I have no clue, but I wouldn't be too worried, 25 psi doesn't sound all that bad at idle to me.

 

The H series bearings have good bit more clearance built in to them. From past experience the stock p series will have anywhere from 1 to 1.5 thousandths clearance and the h series will have in between 2.5 to 3.2 thousandths. It just depends on what end of the spec the housing bores and the shaft is at. But if u are hotrodding it u got the right bearings and around 2.8 to 3 thousandths would be idea for a street motor. But u will need to run a thicker oil. U might wanna try Shell rotella 15w40. We have had some good luck with it, and its not got all of the good leads and all the good lubricating bases taking out to meet emissions because its run in our not so emissions friendly diesels. Its also really high in detergents and if it can withstand the load a diesel puts it through it should be more than adequate for a gas motor. Just my 2 cents.

 

I don't know what you are worried about. 25 psi at hot idle is good. A lot of LT1 owners would kill for that kind of pressure.

 

I believe he's asking for your clearances. I take it from your original post that you put the motor together? You mention the pressure leveled off at 25lbs., but what is the idle set at? Can you trust your gauge?

 

I agree. What pressure do you have @ 1500-2000rpms?

 

Yeah, I have 25-30 very hot idle and as soon as you touch the gas it shoots up to 60-70 @ WOT.

You still need to know what your bearing clearances are, they should have been measured to a minimum of .0005 by whoever selected the bearings.

 

Exactly

 

I really appreciate all the replies. Here are some answers to your questions-In short, I dont know the clearances, the machine shop did the machine work, balancing and sent me the bearings I needed and thats all I know. Between the 7 qt canton pan, oil cooler, lines and 3 quart accusump, it holds about 11 quarts of oil - this is a road race only car, oil level is good on the dipstick with this amount of oil. Its about 25 psi at idle but only goes up to about 32-34 at 2500 rpm (Ive not revved it past that, Ive only done the cam break in procedure so far). My friend and I assembled it, but did none of the machine work. The pressure was verified on the accusump gauge. It idles at about 1000 rpm (not tuned yet).

What gets me is, if the engine is happy at 25 psi at idle, why did it start out at 50-55 psi? An oil temp even up to 300 should only drop your pressure by like 5 psi, even on dino oil. It just doesnt make any sense.
The car is 3.5 hrs away, I travel between there and my home town every other week so I wont be able to get back to it till next monday. Anyway, here is a theory I posted on my 'home' website FRRAX.com, let me know what you think...I appreciate the input-

Heres a theory: The last motor ran perfect for 3 years (see my previous sob story post about when my motor blew up) until I installed the accusump and oil cooler. I ran the car up and down the street a couple of times and had good oil pressure, but never long enough for the oil temp to go up. The first time I took it out on the track and it got hot it blew up. The cooler lines come out of the canton adapter and curl forward between the K-member/frame and the outside of the header (with the orange heat wrap). The lines do not look kinked at all but they are bent around about as tight as they seem to "comfortably" go. It is set up the same way now on the new engine. Now I know this is a long shot... But could the cold thick oil on start up be just barely holding open a partial obstruction in the oil line, then when the oil heats up and thins it loses its pressure and the obstruction starts to close? That would explain BOTH why the old motor blew up and the problem Im having with the new motor. Maybe the only reason this motor hasnt blown is because now it has a high volume pump (yes I know - high VOLUME) and its barely able to produce 25 psi throught the obstruction where the stock pump failed.

I don't know how else to explain how an engine can have 50 psi cold and 25 psi hot, theres no way it should drop that much, even on 10-30 dino oil.

Of course the first thing Im going to do when I can get back up to Ohio next week (where my car is) is try some 15-50 and if it doesnt work or if I see more than a 5 psi drop in pressure when it gets hot is just to swap out the adapter and just put a filter on it and see what happens.

 

Mine is 50-60 psi at cold idle.
After 15mins drops to 20-25
After stop and go traffic and 95+degrees outside it idles between 15-20..
WOT goes to 40-50...

I think your worrying too much...

Cody

 

Normal.

Even so, you should have checked oil clearances when you put it together. That's an important part of building the engine.

 

Stop worrying and once it's up to operating temp start seating the rings, as in, get on it hard. Not redline hard, but don't be a wimp either.

 

Alright guys, thanks for all the input, certainly makes me feel better. I'll let you know what happens.