Possible Cause of High Oil Pressure
Thread Starter
Staging Lane
Joined: Jul 2011
Posts: 68
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Possible Cause of High Oil Pressure Ok, so I swapped a 900 mile LH8 5.3L into a Chevelle. Deleted the DoD with LS7 lifters, LS3 cam gear (to remove the phaser for VVT), LS3 valley tray to block off the oil passages for DoD, and programmed all that stuff out. Also replaced the cam with a custom grind Comp Cams cam.
Having some tuning issues, but my main concern is the oil pressure. Cold start on a hot day it is at 80 psi. When the engine warms, it goes to about 65psi and at 2000 rpm it is up in the 70 psi range.
Too high and not sure why. I'm running a Dakota Digital sending unit and the OHMs check out OK. I'm going to check with a mechanical gauge, but I'm pretty sure the current gauge is reading correctly.
I'm running 5W-30 AC Delco Dexos blend with a Mobil 1 filter. I changed the oil and tried the AC Delco filter. No change.
I'm thinking that the problem is that the LH8 uses a high volume oil pump for all of the DoD and VVT stuff and with all of that deleted, the oil pressure is high. Either that or there is a blockage somewhere.
Ideas? Perhaps the only fix is to pull it apart and change the spring or pump to lower volume. Ugh. It is parked until I can figure this out.
Having some tuning issues, but my main concern is the oil pressure. Cold start on a hot day it is at 80 psi. When the engine warms, it goes to about 65psi and at 2000 rpm it is up in the 70 psi range.
Too high and not sure why. I'm running a Dakota Digital sending unit and the OHMs check out OK. I'm going to check with a mechanical gauge, but I'm pretty sure the current gauge is reading correctly.
I'm running 5W-30 AC Delco Dexos blend with a Mobil 1 filter. I changed the oil and tried the AC Delco filter. No change.
I'm thinking that the problem is that the LH8 uses a high volume oil pump for all of the DoD and VVT stuff and with all of that deleted, the oil pressure is high. Either that or there is a blockage somewhere.
Ideas? Perhaps the only fix is to pull it apart and change the spring or pump to lower volume. Ugh. It is parked until I can figure this out.
Last edited by cgo; Sep 15, 2014 at 09:08 PM.
Staging Lane
Joined: Apr 2013
Posts: 97
Likes: 0
When I first redid my engine I was seeing around 65psi at warm idle and 80+ when at higher rpms. It has since came down to around 50/70, as everything got broken in. I wouldn't worry too much about 70psi.
On a side note, you mentioned a high volume oil pump. I have been told to steer clear of those. Did you maybe mean a high pressure pump? Those are perfectly fine, it's what I have and haven't had any problems.
On a side note, you mentioned a high volume oil pump. I have been told to steer clear of those. Did you maybe mean a high pressure pump? Those are perfectly fine, it's what I have and haven't had any problems.
TECH Resident
Joined: Feb 2014
Posts: 954
Likes: 9
From: Encinitas CA
Funny, I worried a bit about the opposite problem. I have a stock L92 (without DOD), but with VVT. Cold, I see about 55 psi (I live in San Diego, so cold is relative). At hot idle, I see 25 psi. On Freeway at 1800 to 2k rpm, I see maybe 40 psi. I have not verified with a mechanical gauge.
My engine has 150k+ miles with seemingly zero issues, great power, nothing in the oil at my one oil change and never been opened up. Having poked around various boards, including Escalade / Denali boards, it seems I'm within normal specs for my engine. I think there may be a pressure relief set at 56 psi, given I'm not seeing more pressure, even cold.
Doug
My engine has 150k+ miles with seemingly zero issues, great power, nothing in the oil at my one oil change and never been opened up. Having poked around various boards, including Escalade / Denali boards, it seems I'm within normal specs for my engine. I think there may be a pressure relief set at 56 psi, given I'm not seeing more pressure, even cold.
Doug
Thread Starter
Staging Lane
Joined: Jul 2011
Posts: 68
Likes: 0
Thanks for the replies guys, yes, that was a typo. I meant 2000 RPM and yes, it has a stock oil pump, but I read somewhere that the LH8 has a high output pump (not sure if that refers to volume or pressure). I guess it depends on what you read and who you talk to. Normal operating pressures for just about all LS based engines and the trucks is 50-60 psi cold at idle and about 40 - 45 psi at idle when warm. I'm at 80 psi when cold at idle and about 65 psi when warm at idle and back up at 75-80 at highway around 2000 RPM. I haven't got on the throttle at all yet, but I'm afraid of what will happen with the pressure at 5000+ RPM... The relief valve could be stuck or I may need to change the spring to a lighter one.
I just did my first startup last week on my fresh rebuild and I was in those oil pressure ranges too. I was to scared to even break it in properly. I have a 5.7, comp cam, ls7 lifters, trick flow push rods, I do how ever have a high volume pump. You guys think psi will drop after break in, and tolerances open up a bit?
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Thanks for the replies guys, yes, that was a typo. I meant 2000 RPM and yes, it has a stock oil pump, but I read somewhere that the LH8 has a high output pump (not sure if that refers to volume or pressure). I guess it depends on what you read and who you talk to. Normal operating pressures for just about all LS based engines and the trucks is 50-60 psi cold at idle and about 40 - 45 psi at idle when warm. I'm at 80 psi when cold at idle and about 65 psi when warm at idle and back up at 75-80 at highway around 2000 RPM. I haven't got on the throttle at all yet, but I'm afraid of what will happen with the pressure at 5000+ RPM... The relief valve could be stuck or I may need to change the spring to a lighter one.
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IIRC, the DOD/VVT do have a high volume oil pump. They also have an oil relief valve in the pan. If you swap pans, no relief valve = high oil pressure at cold starts.
Do a search here, the valve can be transferred to the new pan by drilling and tapping. Although I believe many are running as is.
Do a search here, the valve can be transferred to the new pan by drilling and tapping. Although I believe many are running as is.
Thread Starter
Staging Lane
Joined: Jul 2011
Posts: 68
Likes: 0
Thanks, yes that is what i thought and was afraid of. We did replace the oil pan with a Mast Motorsports pan and did not know about the relief valve. Looks like i need to pul the engine (or do I? I thought the relinef valve was part of the pump assy. Isn't the pump behind the front cover?) and do the mod. I doubt anyone runs that high of pressure without damage.
Ugh
Ugh
Last edited by cgo; Sep 17, 2014 at 10:22 AM.
Do a search here for VVT or DOD and oil pan. You'll find pics of where the valve goes, info on those who swapped the valve over and those that didn't.
Thanks, yes that is what i thought and was afraid of. We did replace the oil pan with a Mast Motorsports pan and did not know about the relief valve. Looks like i need to pul the engine (or do I? I thought the relinef valve was part of the pump assy. Isn't the pump behind the front cover?) and do the mod. I doubt anyone runs that high of pressure without damage.
Ugh
Ugh