Oil pressure help
Thread Starter
Teching In
Joined: Nov 2022
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Oil pressure help I got a fresh built l83 that I used the original oil pump on but didnt know about the alignment tool until after the engine was disassembled. At startup engine had about 10lbs of oil pressure at idle and would go up as the rpm went up. Pulled it apart and installed a brand new pump same result. Pulled it back apart and replaced the barbell in the back of the block same results. What am I missing?
by replacing the pump, we can prolly safely say it isn't the pump or the o ring.
barbell is never an issue... unless its left out.
next item is did you get a clearances sheet from the rebuilder? specs?
what killed the original engine?
barbell is never an issue... unless its left out.
next item is did you get a clearances sheet from the rebuilder? specs?
what killed the original engine?
Thread Starter
Teching In
Joined: Nov 2022
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unfortunately I was the one that rebuilt it I dont know the back story on the engine before I picked it up it was already apart. I had the block tanked and bored .20 over and new cam bearings installed. All new rods and pistons new oil pan cam and lifters. Dod delete
TECH Apprentice
Joined: Aug 2018
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Did you check the cam/crank journals for diameter? How did they look like when you tore it down?
I tore a 4.3 this summer that had ran for 260k miles and my pressure had fallen to like 7 psi at idle. The cam and rod bearings were gone. Clearance was around 4.5-5 thousands when checked with a micrometer and dial bore guage. I'm just learning how to take measurements, so that was a good exercise for me.
You can use Plastiguage on the main/rods, very economical. Not sure how you would check clearances on the cam w/o a mic/bore guage. You can always take it to local machine shop for measuring, if that's an option.
I tore a 4.3 this summer that had ran for 260k miles and my pressure had fallen to like 7 psi at idle. The cam and rod bearings were gone. Clearance was around 4.5-5 thousands when checked with a micrometer and dial bore guage. I'm just learning how to take measurements, so that was a good exercise for me.
You can use Plastiguage on the main/rods, very economical. Not sure how you would check clearances on the cam w/o a mic/bore guage. You can always take it to local machine shop for measuring, if that's an option.
TECH Resident
Joined: Mar 2012
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From: Texas
I remember that GM made a really big deal about oil pump alignment on the Gen V engines, and OF COURSE they've got a special "Installation tool" to sell you for the low, LOW price of $150...
I've seen the "tool," and it is two metal tabs that go into the timing cover bolt holes that you butt the new oil pump against.
What I have done is match the outline of the old pump mounting points on the block.
If you put the pump back on with the rubber inserts on the bolts, there is little to no movement at all...
Anybody had a problem with low oil pressure after an oil pump change on one of these engines?
I've seen the "tool," and it is two metal tabs that go into the timing cover bolt holes that you butt the new oil pump against.
What I have done is match the outline of the old pump mounting points on the block.
If you put the pump back on with the rubber inserts on the bolts, there is little to no movement at all...
Anybody had a problem with low oil pressure after an oil pump change on one of these engines?
Did you damage the piston squirters when you were stuffing the pistons? Where are you measuring the oil pressure at and what oil temp are you measuring the pressure? There are quite a few places where a small mistake can turn into a large oil hemorrhage. What clearance did you set the mains and rods to? Usually oil pressure issues are either cam bearings not fully seated or mains that are way too loose.
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What is the oil specification for the Gen V/LT engines anyways? I know I've read they require higher pressures for the AFM...but haven't seen a spec.
Oh, I also just realized those engines have a little solenoid on the oil pump. The pump itself is now a vane-type, and resembles the pump of the 4L60e, instead of the gerotor of Gen III/(IV?)
Oh, I also just realized those engines have a little solenoid on the oil pump. The pump itself is now a vane-type, and resembles the pump of the 4L60e, instead of the gerotor of Gen III/(IV?)
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Verdad Gallardo You should be using 0W-20 Dexos 1 Gen 2 for that engine, nothing thinner, you can go up to a 30 or 40 weight oil, but for cold priming you want the 0Wxx. Yep this is a new pump design for the Gen V, it should make between 220-250 kPa in LP mode and 350-400 kPa in HP mode, depending on the oil temp. You are correct this oil pump was started from the hydromatic transmission pumps, Gerotors are really a thing of the past with the amount of oil consumers these engines require.
Correct it is called a VDOP oil pump, they have been around for decades. They are actually used by all OEMs now. Main gallery feedback is a powerful lubrication tool, unlike the older Gerotor pumps that relied on pump out pressure for regulation.
On The Tree
Joined: Jul 2020
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I THINK this is along the same line of question.. I have a recently rebuilt (engine builder) 4.8 gen IV (2013) stock rebuild, I am getting around 9psi at idle, gets better w/ rpm. I know this is not right, looking for issues,suggestions or help to make pressure right? I did do the "trick" of jacking the rear of the truck up (get oil to front) and adding a quart and then turn on and see if pressure is better. it only raised the pressure a lbs or so. any suggestions? I will check with mech gauge in a day or so to verify my Dakota Digital Dash is reading correctly.
thanks!!
thanks!!
Teching In
Joined: Feb 2023
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Gen 3 5.3 fresh rebuild.
I have been reading and studying the LS1 oil flow diagrams.
I believe that leaving the dog bone out will not cause lack of oil pressure, the oil flow is just diverted into oil filter then continues up the oil gallery. If dog bone is left out the oil flow just continues on its intended path. Yes my dog bone is installed.
I am chasing no oil pressure on startup also. I have mechanical gauge in the sender location and front main galley at oil pump.I have primed twice using 3 qts using air over oil and also a pump. I have started and run for about 10 seconds, no pressure and no oil at rockers. I have removed pan and checked fit of o ring, seems to fit well using green o ring. Back together and no dice again. I have new Melling oil pump and new cam bearings and within spec on mains and rod bearings, standard size. I ordered the 2 o rings from melting but just can’t believe that would be the cause zero pressure even if the wrong size was installed. If the black ring is larger diameter then the green one I will try the larger one, regardless no pressure??
I am tempted to pull pump to see if pressure relief is stuck open some how, I am a very capable SBC engine builder including 383 strikers. This is my first Gen 3 engine, every thing was done professionally. Frustrated.
welcome your input.
I have been reading and studying the LS1 oil flow diagrams.
I believe that leaving the dog bone out will not cause lack of oil pressure, the oil flow is just diverted into oil filter then continues up the oil gallery. If dog bone is left out the oil flow just continues on its intended path. Yes my dog bone is installed.
I am chasing no oil pressure on startup also. I have mechanical gauge in the sender location and front main galley at oil pump.I have primed twice using 3 qts using air over oil and also a pump. I have started and run for about 10 seconds, no pressure and no oil at rockers. I have removed pan and checked fit of o ring, seems to fit well using green o ring. Back together and no dice again. I have new Melling oil pump and new cam bearings and within spec on mains and rod bearings, standard size. I ordered the 2 o rings from melting but just can’t believe that would be the cause zero pressure even if the wrong size was installed. If the black ring is larger diameter then the green one I will try the larger one, regardless no pressure??
I am tempted to pull pump to see if pressure relief is stuck open some how, I am a very capable SBC engine builder including 383 strikers. This is my first Gen 3 engine, every thing was done professionally. Frustrated.
welcome your input.
Last edited by 3464EMenlo; Feb 7, 2023 at 05:56 PM. Reason: Gen 3 not gen 5
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
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From: Central Cal.
Gen 3 5.3 fresh rebuild.
I have been reading and studying the LS1 oil flow diagrams.
I believe that leaving the dog bone out will not cause lack of oil pressure, the oil flow is just diverted into oil filter then continues up the oil gallery. If dog bone is left out the oil flow just continues on its intended path. Yes my dog bone is installed.
I am chasing no oil pressure on startup also. I have mechanical gauge in the sender location and front main galley at oil pump.I have primed twice using 3 qts using air over oil and also a pump. I have started and run for about 10 seconds, no pressure and no oil at rockers. I have removed pan and checked fit of o ring, seems to fit well using green o ring. Back together and no dice again. I have new Melling oil pump and new cam bearings and within spec on mains and rod bearings, standard size. I ordered the 2 o rings from melting but just cant believe that would be the cause zero pressure even if the wrong size was installed. If the black ring is larger diameter then the green one I will try the larger one, regardless no pressure??
I am tempted to pull pump to see if pressure relief is stuck open some how, I am a very capable SBC engine builder including 383 strikers. This is my first Gen 3 engine, every thing was done professionally. Frustrated.
welcome your input.
I have been reading and studying the LS1 oil flow diagrams.
I believe that leaving the dog bone out will not cause lack of oil pressure, the oil flow is just diverted into oil filter then continues up the oil gallery. If dog bone is left out the oil flow just continues on its intended path. Yes my dog bone is installed.
I am chasing no oil pressure on startup also. I have mechanical gauge in the sender location and front main galley at oil pump.I have primed twice using 3 qts using air over oil and also a pump. I have started and run for about 10 seconds, no pressure and no oil at rockers. I have removed pan and checked fit of o ring, seems to fit well using green o ring. Back together and no dice again. I have new Melling oil pump and new cam bearings and within spec on mains and rod bearings, standard size. I ordered the 2 o rings from melting but just cant believe that would be the cause zero pressure even if the wrong size was installed. If the black ring is larger diameter then the green one I will try the larger one, regardless no pressure??
I am tempted to pull pump to see if pressure relief is stuck open some how, I am a very capable SBC engine builder including 383 strikers. This is my first Gen 3 engine, every thing was done professionally. Frustrated.
welcome your input.