ZONES89RS

iTrader: (25)

Alright, here is the deal, my 6.0 is stock from a 02 service truck, when i got the engine, i put a used oil pump from a LS1(12 K miles) in it, shimmed the spring .020 and installed it with the Trex cam.

It runs great and has ALWAYS lost oil pressure as the oil breaks down, usually idle is in the neighborhood of 50 pounds and jets to 80 when in gear in the revs.

Now, as oil breaks down, idle will lower to 45, then 40 usually as the engine continues to be abused, well, the oil has been down to 40or so and i am ready to change it, but now i went for a ride and when i cam back, it was at 350 or so after rowing through a couple gears and now in the revs it seems to only go to 65 pounds, i cannot hear any engine noise to see if there was a chance of a spun bearings, but i am thinking that it is a early sign of some failures somewhere.

Anyone else ever have this issue? I am going to change the oil today, but i have never had my pressure go so low since the car has had this engine installed, just has me worried.

Detoxx03

iTrader: (14)

I had a low oil pressure issue and it turned out to be the sending unit

MM98

iTrader: (13)

Have you checked the oil level? Could just be down a quart.

Darkman

iTrader: (2)

In addition to the sending unit it could be a deteriorating ground. Check the goround starting with the negative battery strap and the grounds on the back of the heads.

xpndbl3

iTrader: (23)

Running it too rich and getting fuel contamination in the oil?

ZONES89RS

iTrader: (25)

Been slightly lean, but i guess i just drove the hell out of the oil till it just broke down that bad, did the oil change and it is right back up to where ti was, pressure damn near hit 100 pounds when the oil was still cool, but everything is as it should be now, just never had it go down so low, was a scare since i am trying to finish the other project and cannot afford to get another 6.0 right now if this one dives.

01ssreda4

iTrader: (96)

Why are you hitting 100 pounds? The relief spring should be opening before this?

$750 L98

iTrader: (7)

Wacky, I thought max pressure was some where around 75-80psi. Now my stock LS1 idles at 35psi hot, and runs 60psi wot, my LQ4 runs 40psi hot idle and ~65psi wot with a supposed LS6 pump.

ZONES89RS

iTrader: (25)

I shimmed the spring to increase oil pressure.

01ssreda4

iTrader: (96)

Why would anyone desire 100lbs of pressure? Could this be contributing to your other problem in any way?

ZONES89RS

iTrader: (25)

No one desires 100 pounds of oil pressure, read everything:

01ssreda4

iTrader: (96)

Oh I'm plenty literate, I saw where you said it was cold oil. My point was, and you must have mistaken the courteous nature of my post for being dumb, are you sure you didn't **** up and shim the spring too much? Not saying this would contribute to your other problem but it was a thought. Why would anyone desire 100lbs of COLD oil pressure? Are your bearing tolerances set up for this? I once watched a standard pressure Melling idle at 32 lbs. on a mechanical gauge, then gracefully climb to about 70 lbs at 4500 rpms. It would not climb higher then 70 lbs even if you kept revving. I assumed this was where the relief spring opened, and it seemed like plenty of pressure for any stock engine. Why would anyone desire more pressure then this?

So are you saying bc the oil is cold the spring works differently or at a different pressure? Quite honestly I don't follow where you are going with any of this.

ZONES89RS

iTrader: (25)

Oil when cold is thicker, once warmed it is thinner. I said near 100 pounds, that does not mean 100, it was a touch over 90, once warm it is about 75 max or so. As for is it clearanced? No, it is a junk yard engine, so being from a service truck, i make the assumption that the wear from its work horse duty made more clearance than factory has off the show room floor. The pump is a stock replacement i shimmed .020 to get a bit more out of it, it is where i want it.

The only issue with near 100 pound i think would be the fact that it robs power, but if it was always rocketing to 100 or near it, i would consider that a issue.

Sorry i came off to you as being an *******, thought you might have not read the entire post.

Whiteaw57

iTrader: (2)

yeah i kinda agree with 01ssreda4. 100# even cold is high for any street clearanced engine. I know race engines obviously run that range and rule of thumb is ten pounds per 1000 rpm but my 98 camaro with a 2000 ls1 has 50 cold at idle and 35 or so idling hot. really more like 38. and of course 65 at higher rpm. but over the life of the oil I haven't seen any change (pennzoil platinum 5w-30)

01ssreda4

iTrader: (96)

Perhaps the flucuating oil pressure as the oil wears/ages is either (in my mind) A. subpar oil or B. and indication that the motor is "well worn." Other then that I wouldnt really worry about it honestly.

Whiteaw57

iTrader: (2)

^^^^^^^x2

01ssreda4

iTrader: (96)

BTW, are you running Supertech oil? That **** is crap. Makes every engine I put it in noisy. I have banned Supertech motor oil in my garage.

ZONES89RS

iTrader: (25)

Exactly, the engine is a service truck motor, nothing well maintained and what not. I am not worried about it except it was weird that it was down to 35 or so, never been that low, was just old oil that has seen abuse, there is not a single instance my car is not stared and taken to 7200 RPM, so the oil breaks down, i only run Valvoline, Castrol and Mobil. Anything else that is regular oil will not go in my lawn mower asides from Chevron or Havoline if i just have no other option.

Like i said, max pressure is about 75 in the revs with 10w40. The next pump i shim will be about .015 to see what the difference is.

01ssreda4

iTrader: (96)

Actually I consider a commercial vehicle better maintained then some engines bc service (oil changes) is paid for by the company and required to protect the company's investment. Guess it depends on the policies of the exact company.

ZONES89RS

iTrader: (25)

Hell, the engine had rust in 2 cylinders and what not so i just upped the pressure to hope for the best, i cannot afford the race engines, just the junk yard pieces. Hell, more pressure has to be good when you consider the crank gets oil last.