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So I pulled a lq9 from a local lkq. I swapped it into my third gen Camaro. Before dropping the motor in I put in a new oil pump o ring and a billet oil galley barbell. When first firing it up it has 30 psi but after it warmed up it dropped to 15-20 psi. With the engine still in the car I installed a new melling oil pump and oring. Still did the same thing so I figured it was time for a rebuild. I took the engine back out and installed all new bearings and verified proper clearance. I just got the motor back in and it is still having the same oil pressure issue. I have checked with a mechanical gauge and I am running 5w30 oil. Any suggestions?
What did you set the bearing clearances at? Did you get a real good look at the cam bearings? Do the lifter bores look good?
I replaced the cam bearings with a set of dura bond bearings. I used plasti gauge for the bearings which all seem less than .002”. The lifter bores appeared to look good. I also completely resealed the engine including a new cam retainer plate.
Oil "barbell" diverter? Diverter port plug correct depth in the hole? Press-in oil galley plug in the front of the block intact? Is your oil cooler port (if you have one) adapter/delete clear? Rear cover gasket intact? Rear oil pressure sensor SCREEN? There are surprisingly many was of losing oil pressure in these engines.
Did you shim the oil pump during installation? Did you use the correct o-ring? Are you sure you didn’t pinch it? Did you try one of the many pump brace such as BRP or Improved Racing? Cheap insurance < $30
Check it at the front port on the drivers side. It's a several inches from the front of the engine. This is true, pre-filtered oil pressure that the pump is actually pumping. The factory sender at the top of the engine, and reads filtered oil pressure. This can vary with screen condition, and quality of filter (variable restriction)
Oil "barbell" diverter? Diverter port plug correct depth in the hole? Press-in oil galley plug in the front of the block intact? Is your oil cooler port (if you have one) adapter/delete clear? Rear cover gasket intact? Rear oil pressure sensor SCREEN? There are surprisingly many was of losing oil pressure in these engines.
Originally Posted by grinder11
I guess my question is what gauge read these readings? OEM, mechanical, etc?
Originally Posted by Jimbo1367
Did you shim the oil pump during installation? Did you use the correct o-ring? Are you sure you didn’t pinch it? Did you try one of the many pump brace such as BRP or Improved Racing? Cheap insurance < $30
I installed a billet barbell oil diverter before I ever put the engine in the car and took it back out and re installed it during the rebuild. I didn’t shim the oil pump but i did install as per Mellings instructions. I don’t think the oil pump is the problem because I had the same symptoms with the factory installed oil pump. I know for sure I have the correct o ring and have installed it correctly because I did it while the engine was in the car and again once I had the engine out and on the stand, with the same symptoms. The only thing I haven’t checked is the oil pressure sensor screen because I didn’t think an 03 lq9 would have one. Pressures have been checked with the gauge in the car and a mechanical gauge.
Check it at the front port on the drivers side. It's a several inches from the front of the engine. This is true, pre-filtered oil pressure that the pump is actually pumping. The factory sender at the top of the engine, and reads filtered oil pressure. This can vary with screen condition, and quality of filter (variable restriction)
I measured at the front port and I got a steady 40 psi cold and warm. I got 40 when cold at the top rear and 18 when warm.
I measured at the front port and I got a steady 40 psi cold and warm. I got 40 when cold at the top rear and 18 when warm.
The front port is always a bit higher than at the sender unit. I saw between 5 and 10lbs higher at the front port, because it is a pre filter location, and the OEM location at the top rear is after the filter. But I never saw 40lbs cold. That sounds low to me if your bearings are truly only .002". My opinion, YMMV.
Have you found the issue? I have a similar problem, but worse, 20 psi at the front port cold and 5 psi up top at idle. Front port will go to 40-50 revved up, top port only maybe 20. No screen in the top port. Runs great, and quiet. Not much oil on the rockers but there's some. I've never let it run long enough to check hot pressures but I'm sure they're horrible. I've changed the cam retainer plate, front plug is in place, AFM towers plugged, barbell in place, new Melling 10295, etc.
I wonder if there might be an issue with the Holley knockoff pan from Amazon? Decent pressure at the front port seems to show the pickup/o-ring is OK. Goes downhill from there.
Did you install the barbell fat side in first? Also what brand? What brand oil filter? What lifters are you using?(axle oiling?) Do you have a oil cooler or adaptor other then the factory style? If all this is good the bearing are most likely the culprit. Plasti gauge will not give you the actual readings like a bore gauge will.
Last edited by jasons69chevelle; 03-09-2023 at 06:23 AM.
02-26-2023, 08:19 PM
Low oil pressure after rebuild 
