I'm posting this here rather than the C5 section because it is LS3 related and (I'm hoping) there will be a better knowledge pool here...

I have a C5 that I put an LS3 into about a year ago. The motor was taken out of a 2008 Corvette with 832 miles in order to put in a blower motor. The owner then sent the motor to Precision Engine Service in Austin, TX to have the reluctor wheel changed out to a 24 tooth for installation in a C5. I then purchased it from the owner and had it shipped to California...

So far, stock motor, 832 miles, changed reluctor to 24 tooth. Now, I had some mods done prior to installation...

New Cam (224/234 .610/.586 116LSA)
Patriot Xtreme Springs
Yella Terra Rockers (1.7)
Texas Speed push rods
Katech ported/blueprinted LS6/LSx oil pump
Katech C5R Timing Chain

Now, it's been a year and about 5,000 street miles. I've been down the drag strip 12 times. I've run about 150 auto-x laps (laps, not events). Now my oil pressure seems low. To be honest I never really paid any attention until 2 mechanics said it seemed low. It starts up at about 40psi, but when it warms up...

WARM idle at 14 psi...



WARM cruising at 27 psi...



As advised by my mechanic, I switched oil from Mobile1 5w30 to Amsoil 10w40. It brought the warm idle up to 22 pounds (no pic) and warm cruising up to...

New WARM cruising at 33 psi...




These numbers still seem low. One mechanic said, "just keep an eye on it". The other said he suspected the cam bearing and said the engine should be pulled and re-machined.

Before I go pulling the motor, I am hoping to get some feedback on possible causes. And advice.

 

I'd send an oil analysis to Blackstone to see if there is bearing material in the oil.

It is lower than normal but I believe it is still within spec although I question the spec being so low. For the LS1/2/6/7 it's:

Oil Pressure (Minimum - Hot):
1,000 RPM = 41 kPa / 6 psig
2,000 RPM = 124 kPa / 18 psig
4,000 RPM = 165 KPa / 24 psig

 

yes those #s are a lil low but not yet low enough to be scared yet. a new set of bearings will more than likely bring it up. but with the mileage you report its a lil soon to have wore bearings down that much allready.

 

I'd wonder if the C6 sending unit impedance (electrical) isn't correct for the C5 gauge? Have you used a mechanical gauge to check the pressure at the port?

 

I am using a C5 pressure sensor mounted to the TPE relocation kit (side of pan). I know that if the sensor fails, it reads 80psi. However, can the sensor start readin low as it starts to go out?

 

Never seen that behavior on one. Just pegging at 80 when it tanks.

 

Other possible causes of reduced oil pressure? Failing oil pump? What are the chances with only 5-6000 miles?

 

I had a C5 that the factory gauge did peg, when the sender went south; but I would put a good mechanical gauge on it first , to condem or confirm the factory gauge.

 

That would be much cheaper and easier to check before you get into the motor. Especially if you have no external signs of low oil pressure (ticking, etc).

 

I just had a friends Ls3 doing the same thing, the dealer replaced the cam and lifters due to damage to lifters, after assembly my Buddy noticed low oil pressure, they told him it was fine. he drove it for 23K miles, I took it apart to install a cam and found the wrong Oring in the oil pump pickup tube. it was sucking air!!
We had to replace the cam bearings and rod and mains, they were down to the copper!!!

 

I would install a mechanical test gauge before I'd do anything else.

 

Where would I test? At the top of the block where the OPS normally sits?

 

What oil filter are you using? I've read on this forum where some filters yield a low pressure (M1?). I've read where one forum member changed to the AC filter and the pressure returned to normal.

 

there is a plug on the drivers side front on the oil galley, thats one that I've used to prime prior to start.

 

That is what I'd do as well. Sounds like your bearing clearances are higher than normal and you have high flow, but little pressure. The low pressure will result in a less than adequate film layer under high bearing loads (e.g. the drag strip). I think going up to a 10w40 and one with high ZDDP was a good call (and if you are not getting it at wholesale via the Preferred Customer program give me a shout) and it looks like it helped your pressure some, but it is still below normal.

I'd get oil analysis done to see if you have problems.

I lost my first motor (prompting me to switch to AMSOIL) and I'm here to tell you, cheaper to rebuild now than to have a piston rod rotate out the side of the block...

 

As alluded to above, have you changed oil filters lately? If so, that could be the problem.

 

I had low oil pressure on my 2004 GMC 2500HD with the 6 litre engine. We changed the oil pump and that solved the problem. The truck had about 250,000 miles when the problem surfaced. Truck is doing fine today with almost 400,000 miles... Great truck by the way!

 

It would be helpful also to know what your oil temps are, as this also has a large effect on viscosity , subsequently , pressure is affected. All that being said, you are still above minimum pressure per gm specs. I would test as others have suggested before I would open up the motor.