Strange change in oil pressure
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Joined: Jun 2013
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From: Nebraska, The Good Life
Strange change in oil pressure This is the LS2 in my 06 GTO.
I've had the car since 2010, had 27k on it when I got it. It was stock then. Now it has 46k on it and I've added a TVS2300 Magnuson and headers and a tune of course. It also has 1.8 roller rockers and heavier valve springs to help get a little more out of the stock LS2 cam. In the entire time I've had it it has had a slight tick. Never got worse, was sometimes intermittent, car always ran great. The really odd thing is it ALWAYS ran at 45 psi. 45 cold, 45 hot, 45 at idle, 45 while cruising, 45 at high RPMs.
I recently decided to go after the tick. I assumed it was a lifter. Tuner thought it was a valve in one of the heads even though compression and leak down tests showed all cylinders were strong. Anyway, I pulled the heads and had them gone through, light valve job, surfaced and I installed new GM LS7 lifters. Got it all back together and it still has a tick but now I wonder if it is just a louder than average normal LS engine sewing machine sounds instead of an actual tick. Runs fine. The LS1 in my 04 GTO is much quieter.
Took it for a drive for the first time since the new lifters went in. Ran just great. BUT, I noticed that the oil pressure was a little lower than before while cruising, just above 40 (about 1500 RPMs). At a full hot idle, psi was down to about 20. Rev the engine and oil pressure goes up to just over 45. In the entire time I've owned the car I have NEVER seen the oil pressure gauge move at all, always deadset on 45. Now it is moving. Never dipped low enough to be a concern, but still, a real change from before. Oil is Valvoline 5w-40 full synthetic "Euro" oil, changed it right after I buttoned up the engine.
Could I have a failing oil pump now? I have a Melling M295 pump sitting in a box I could throw on. Don't see how the lifters could have caused this change in oil pressure, but maybe one or two of them are slightly undersized and allowing pressure to bleed off? Could that "Euro" oil just be too thin? It is rated for diesels which I'd think would make it somewhat more robust than average oil.
Really confused by this change in oil pressure readings.
I've had the car since 2010, had 27k on it when I got it. It was stock then. Now it has 46k on it and I've added a TVS2300 Magnuson and headers and a tune of course. It also has 1.8 roller rockers and heavier valve springs to help get a little more out of the stock LS2 cam. In the entire time I've had it it has had a slight tick. Never got worse, was sometimes intermittent, car always ran great. The really odd thing is it ALWAYS ran at 45 psi. 45 cold, 45 hot, 45 at idle, 45 while cruising, 45 at high RPMs.
I recently decided to go after the tick. I assumed it was a lifter. Tuner thought it was a valve in one of the heads even though compression and leak down tests showed all cylinders were strong. Anyway, I pulled the heads and had them gone through, light valve job, surfaced and I installed new GM LS7 lifters. Got it all back together and it still has a tick but now I wonder if it is just a louder than average normal LS engine sewing machine sounds instead of an actual tick. Runs fine. The LS1 in my 04 GTO is much quieter.
Took it for a drive for the first time since the new lifters went in. Ran just great. BUT, I noticed that the oil pressure was a little lower than before while cruising, just above 40 (about 1500 RPMs). At a full hot idle, psi was down to about 20. Rev the engine and oil pressure goes up to just over 45. In the entire time I've owned the car I have NEVER seen the oil pressure gauge move at all, always deadset on 45. Now it is moving. Never dipped low enough to be a concern, but still, a real change from before. Oil is Valvoline 5w-40 full synthetic "Euro" oil, changed it right after I buttoned up the engine.
Could I have a failing oil pump now? I have a Melling M295 pump sitting in a box I could throw on. Don't see how the lifters could have caused this change in oil pressure, but maybe one or two of them are slightly undersized and allowing pressure to bleed off? Could that "Euro" oil just be too thin? It is rated for diesels which I'd think would make it somewhat more robust than average oil.
Really confused by this change in oil pressure readings.
Last edited by Rich-L79; Apr 14, 2025 at 08:54 AM.
Thread Starter
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Joined: Jun 2013
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From: Nebraska, The Good Life
Maybe I should change the oil pressure sensor while I'm at it. Since the gauge I have reads via OBDII, perhaps I should connect a physical gauge at least temporarily to see what may really be going on.
Thread Starter
TECH Resident
Joined: Jun 2013
Posts: 814
Likes: 231
From: Nebraska, The Good Life
Ha. No way I can change the sensor without pulling the blower (again). It seems to be reading okay, HPT connected confirms oil pressure is there and looks fine. But pressure is on the low side of normal so I think I'll put on the Melling M295 pump I have sitting on a shelf along with a new timing chain.
Last edited by Rich-L79; Apr 14, 2025 at 08:55 AM.
