I just had a new Iron 403 built with all good internals. Callies crank and rods, Wiseco pistons, ACL bearings and all blueprinted, square decked, torque plate honed etc. All done by a very reputable builder in Houston (HKE).
I had a problem with the original oil pump in this motor and discovered that there were a few little metal flakes holding the bypass piston down in the oil pump just enough to bleed pressure at idle making it low and closed enough to allow the pressure to get to in excess of 90lb. I replaced the pump with a brand new one and my idle pressure came way up. The problem now is I was logging the car on a few hard runs and noticed the oil pressure rises to 38psi at 2500rpm and then stops climbing at a decent rate. At 3500rpm, it is at 41psi, at 4500rpm it is at 45psi and from there it no longer reads 10psi per 1krpm. At 5600rpm it is at 46psi and at 6500rpm it is only 39psi. It has more pressure at 4600rpm than at 6500. I know this pressure is reading at the back of the motor, but this drop is significant no matter where you are measuring from. I am figuring you are going to tell me to check the pressure on the side of the block with another gauge, but the pressure consistently flattens out in the upper rpms on every run when it should build. It seems that there is a restriction at high rpm preventing flow. I made sure the spacer plate for the pump wasn't backwards or upside down and I know if it is, it would probably cause this problem. The other thing that I think would cause this problem is if the pickup tube was too close to the floor of the pan. Any other suggestions?
One of these days, maybe I can just drive and enjoy this car.

 

Since I was able to make too much pressure with the last pump, I figure it has to be the spacer plate is bass ackwards.

 

Are you running a double roller? Here are a couple of things I'd suggest, but you probably have them covered:
1: Have you checked the pressure with a mechanical guage? The OPS has been known to be problematic.
2: As you stated, check the spacer plate, but also make sure it's lined up perfectly with the hole. I have read that some use a touch of RTV between the plate and the block.
3: O-ring. After a hard run, check the dipstick for bubbles. You may be aerating the oil. Be careful of running it hard with oil pressure as low as your reading.
4: When you replaced the pump did you use a high volume, high pressure, or an oem unit?

To give you some perspective I'm running an LPE 403 with an LPE high volume pump. (I think it's the LS4 pump). I'm also using an external oil cooler (an LPE). With 10w-40 Redline yesterday at hot idle I saw 42psi, and at WOT up to 80+psi on the DIC.

 

Blownbluez06,

I’ve followed your thread on the engine build, nice set of pictures, thanks for sharing. Sorry to hear you are having the oil pressure issue. My guess from here in cyber space would be aeration of the oil. The pressure curve typically looks like what you described. Good pressure at idle, increasing to a point as rpm increase and then the fall off at higher rpm. Finding the cause can be a challenge.

Assuming it is aeration;

• Does the engine have a windage tray installed?
• Anything that would restrict oil flow back to the pan?
• Pickup tube not positioned properly?
• Pickup tube attachment to the pump leaking?
• Cracked pickup tube?
• The pump body having a leak somewhere on the inlet side?

Please keep us posted on what you fine, and good luck.

Eric D

 

Man, I feel for you.

You have had the rack out of your car more than anyone on this forum. I bet you can remove it with your eyes closed. Good luck to you!

 

Well, any compromise on the pickup side will cause low idle pressure for sure except maybe the clearance between the pickup and the bottom of the pan.
When I had the other pump in, the piston was stuck barely open and it bled off pressure at idle causing low idle pressure and didn't open enough at upper rpms causing high oil pressure. The high pressure tells me 2 things. 1 that the engine doesn't have any oil leaks and 2 that a stock pump should be able to create that kind of pressure. Given the fact that I have been in the motor and replaced the oil pump, that tells me that the most likely culprit is the spacer plate being upside down and blocking the flow of the oil into the motor. This would cause excessive pressure at the pump and cause the bypass to open and bleed off some which would explain the flat pressure from a certain rpm on. The o-ring is definitely on properly and not pinched. I will be tearing it down (hopefully for the last time in a good while) tomorrow. I will certainly report back.

 

Thanks man.

Now I can do it with my eyes closed and a broken finger!!

 

Even though it's going to be around 105° tomorrow, I'm going to take the day off and tear this apart one more time (famous last words!). I'll let you know what I find, but as you know I have a pretty good idea. After I confirm it, I'm going to beat my own @ss! Video of that coming soon!

 

I'm not so sure I'd want to see that! I would like to see the video of your car hauling @ss!

Eric D

 

Well, the spacer plate was in correctly. I am picking up the high volume pump in a couple of hours and putting the car back together. I found nothing else wrong. I notice on my logs that the pressure really drops when the oil gets hot. I have Havoline oil in the car for break in and will change to 10/30 Mobil1 when I change the oil. I will change the oil soon after I get the new pump in. I want to measure the difference from each.

 

The car is 95% back together. I will finish putting it together tomorrow and let you guys know where I end up.

 

Guys, I know this thread is old, but I was just reminded that I never reported the outcome. I followed Andy's recommendation and got the high volume oil pump from GM. The part# is 12571885 and I believe it was discontinued when I bought it, but they can cross reference it for a valid substitute. It worked like a charm. With the engine fully warmed up, my oil pressure at 6600RPM was 84psi.

 

Thanks buddy i needed that mine is doing the same thing.

 

Is there any downside to too much oil pressure? I also have the LS4 oil pump you have. I installed it a few years ago when I put my cam in because I was doing HPDEs and had an oil cooler. On track w/ oil at max temp (around 270) the pressure never dropped below 50 psi.

Now that my car is a street car again and the oil cooler has been removed I'm seeing 53psi hot idle and cruising pressures in the mid 60s. When I floor it the needle pegs to 80ish.

I'm going to be swapping H/C again in the future and am considering a ported LS6 pump to get the pressure back in the "normal" range. But... if I can get a clear answer about the pressures I may keep the LS4 pump in.

 

The LS4 needed the added oil flow primarily due to active fuel management. The circuitry for this feature uses engine oil to control it. The LS1 does not have this feature nor does it require the added pressure that pump part number 12571885 provides.

There seems to be this recurring misconception on many things where if a little is good then more has to be better. This is false on a number of areas, like torque values, tire air pressure, bearing grease, fluid levels in general, and yes, even oil pressure.

 

I understand that aspect... but when you're running an aftermarket oil cooler which causes pressure drop, and getting the car to 250+ oil temps regularly the LS4 pump was perfectly suited to the car.

Now that I'm not running HPDEs in it (have a dedicated track car) and have since removed my Dewittes radiator w/ EOC the oil pressure seems high to me.

I'll probably throw in a ported LS6 unit when I do some AFRs this winter and pull my G5-X2 for a more moderate cam.

 

I understand your point about the oil cooler possibly adding some restriction reducing the pressure a measurable amount. However, you could have compensated by shimming the relief valve. The engine didn’t require more oil volume. Adding a larger volume pump draws more hp to run, can increase oil temperature, and increase oil aeration. The end results, it could lead to major engine damage.