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Thread: New ls3 engine / low idle oil pressure

  1. #1
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    Default New ls3 engine / low idle oil pressure

    So I'm getting low oil pressure at idle 7-15psi, but as soon as I give it any bit of gas it increases for example while crusing 28-35psi and at WOT 53.8psi

    I have about 1,5xx miles on the new engine
    It is 6.2 core that was machined/cleaned up with new rod and cam bearings
    New melling oil pump, new lifters, new btr stg2 cam, new gaskets, new pushrods,new pistons, new springs, rockers,etc.

    I've done an oil change and filter change, even cut open the old filter and didn't find any metal specks/flakes

    I've also confirmed the readings with a manual pressure guage.

    The motor sounds healthy no tapping or knocking, but I've parked it until we can figure it out

    Both the builder and I are kinda stumped, any ideas?

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    Administrator Chewy's Avatar
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    Quote Originally Posted by SpeedDemon View Post
    So I'm getting low oil pressure at idle 7-15psi, but as soon as I give it any bit of gas it increases for example while crusing 28-35psi and at WOT 53.8psi

    I have about 1,5xx miles on the new engine
    It is 6.2 core that was machined/cleaned up with new rod and cam bearings
    New melling oil pump, new lifters, new btr stg2 cam, new gaskets, new pushrods,new pistons, new springs, rockers,etc.

    I've done an oil change and filter change, even cut open the old filter and didn't find any metal specks/flakes

    I've also confirmed the readings with a manual pressure guage.

    The motor sounds healthy no tapping or knocking, but I've parked it until we can figure it out

    Both the builder and I are kinda stumped, any ideas?
    Did you call Melling? I have a Melling pump and cold at idle itís 50 or more if memory serves.


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    VIP Member STL_G8GT's Avatar
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    Oil Pick-up oring double checked?
    2009 PBM G8 GT
    Pat G 218/226 & TSP Dual 660s, ARP Bits, DSteck Tuned, Magnacharger Chrome 2300 1:1, RCR Ported/Polished TB, Blower, & L92 Heads w/ LS3 intake valves, Smith Brothers Trunion Bushing Kit, ARH 1 7/8 Magnaflow MidMuff/Solo Axlebacks, RotoFab, VaporWorx PWM 1:1 fuel system, ID1050x injectors
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    Originally Posted by TonyKarter
    Anyone who has ever worked on a car has been in your position, and sitting cross-legged on a concrete floor with a dim shop light is its own kind of hell... Chalk it up as one of the rites of passage.
    RIP Charlie - GRRRR8
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    @ Chewy: No not yet but I guess I will just in case the oil pump did fail. Also to add more mystery to this puzzle.....when I start up cold, the oil psi seems to be in the range of about 38-45psi

    @ STL_G8GT: Hmm I haven't checked yet but, I thought once it's in there it would be hard to damage. Also any idea if theres anything that what would cause one with only 1,5xx miles to just tear???
    Last edited by SpeedDemon; 06-06-2018 at 06:09 PM.

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    VIP Member STL_G8GT's Avatar
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    Quote Originally Posted by SpeedDemon View Post
    @ Chewy: No not yet but I guess I will just in case the oil pump did fail. Also to add more mystery to this puzzle.....when I start up cold, the oil psi seems to be in the range of about 38-45psi

    @ STL_G8GT: Hmm I haven't checked yet but, I thought once it's in there it would be hard to damage. Also any idea if theres anything that what would cause one with only 1,5xx miles to just tear???
    Nothing that would tear it, but there were more than 1 size included with the pump depending on pick up tube and pump.... If the wrong one is used, the oil tube will suck air at idle and build some pressure under load/at speed. Depending on install, I suppose it could be torn or sliced during insertion causing the same effects.

    Research oil pick-up oring low pressure and ls engines and you'll see a lot of information.

    I reused an oring on my sierra cam swap and had a very similar issue. Replaced the oring and issue went away.

    Not promising you that's your issue, but it definitely checks all the boxes.

    Also, there is a bypass in the g8 pan for the afm/dod stuff, guys usually plug that I believe. I'm not sure if yours has that or not.
    2009 PBM G8 GT
    Pat G 218/226 & TSP Dual 660s, ARP Bits, DSteck Tuned, Magnacharger Chrome 2300 1:1, RCR Ported/Polished TB, Blower, & L92 Heads w/ LS3 intake valves, Smith Brothers Trunion Bushing Kit, ARH 1 7/8 Magnaflow MidMuff/Solo Axlebacks, RotoFab, VaporWorx PWM 1:1 fuel system, ID1050x injectors
    Mike Norris Motorsports Catchcan, AEM 30-4100, JHP Boost/Fuel Gauge Pod
    TSW Nurburgring Matte Gray 18" w/Nitto 555 & 555R, Satin Black SS Brembo Fronts, BMR Trailing Arms, Pedders Sway Bars, Whiteline Bushings
    Gloss Black Valve Covers, 6k HID, V6 Handles, Interior/License Plate LEDs, Debadged, Holden Black Trim, Polk Dxi, GXP diffusor, a few bits from Crazy Paul

    Originally Posted by TonyKarter
    Anyone who has ever worked on a car has been in your position, and sitting cross-legged on a concrete floor with a dim shop light is its own kind of hell... Chalk it up as one of the rites of passage.
    RIP Charlie - GRRRR8
    RIP Chris Wells - Panzer Leader

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    I dropped the pan and swapped o-rings and even blocked off the DOD oil pan relief valve......

    Still getting 7-11psi idle....anything else I can check?

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    Moderator, Retired -Ray-'s Avatar
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    In my opinion, you have either a bad oil pump, or excessive clearance in bearing journals. Pressure is being bled off somewhere.
    Rest in Peace Charlie!

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    VIP Member norm8332's Avatar
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    What are you using to read the pressure? Maybe it's a sender issue.
    08 G8 GT: MagnaCharger TVS MP1900 10psi, LS9 cam, 72# injectors, Roto-Fab CAI, SLP Headers, Corsa Catback, etc.
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    VIP Member STL_G8GT's Avatar
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    Quote Originally Posted by SpeedDemon View Post
    I dropped the pan and swapped o-rings and even blocked off the DOD oil pan relief valve......

    Still getting 7-11psi idle....anything else I can check?
    I'm with Ray now that those things are taken care of. Did you see what I was talking about with different orings? They're, thankfully, usually different colors. May be worth a note to Greg@Pace.
    2009 PBM G8 GT
    Pat G 218/226 & TSP Dual 660s, ARP Bits, DSteck Tuned, Magnacharger Chrome 2300 1:1, RCR Ported/Polished TB, Blower, & L92 Heads w/ LS3 intake valves, Smith Brothers Trunion Bushing Kit, ARH 1 7/8 Magnaflow MidMuff/Solo Axlebacks, RotoFab, VaporWorx PWM 1:1 fuel system, ID1050x injectors
    Mike Norris Motorsports Catchcan, AEM 30-4100, JHP Boost/Fuel Gauge Pod
    TSW Nurburgring Matte Gray 18" w/Nitto 555 & 555R, Satin Black SS Brembo Fronts, BMR Trailing Arms, Pedders Sway Bars, Whiteline Bushings
    Gloss Black Valve Covers, 6k HID, V6 Handles, Interior/License Plate LEDs, Debadged, Holden Black Trim, Polk Dxi, GXP diffusor, a few bits from Crazy Paul

    Originally Posted by TonyKarter
    Anyone who has ever worked on a car has been in your position, and sitting cross-legged on a concrete floor with a dim shop light is its own kind of hell... Chalk it up as one of the rites of passage.
    RIP Charlie - GRRRR8
    RIP Chris Wells - Panzer Leader

  10. #10
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    1.I used a red oring for the oilpump

    2. I can read the oil pressure value with my torque app and Bluetooth OBD2 or with a manual guage and I get roughly the same values

    3. Can you guys help me wrap my head around how the oil pump could be the cause ? The buddy who built it for me said the pumps usually either work or don't and that since it's increasing 10psi per 1000 rpm's it should be working fine??? I'm not an expert at these things lol just trying to understand what could cause a pump to have low pressure only at idle.... ???

    Also I want to thank everyone for thier help so far, it really means a lot!

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