vladsvt

I've been searching around for about three days now.

Basically I bought a corvette with some issues. One of them is low oil pressure.

Background: This motor was built by ARE sleeved ls1 with forged internals. Anyway doesn't really matter. The guy I bought the car from had this problem and it started out about 2 years ago (but he rarely drives it) Since then he had low oil pressure.

Cold pressure about 1/2 off the gauge (somewhat normal)
Once the car gets warm and to its full temperature the oil pressure drops, and once its been idling or if I drive it the low oil pressure light comes on and the oil pressure drops to about 5-6psi. It stays there.

What has been replaced:
Oil Pump (about 3,000 miles ago)
Sending unit (less then 500 miles)

I'm stumped to what can it be. I've read about those o rings, but can they really cause this much low oil pressure???

The car drives and idles fine (no weird noises or anything) and the guy before me drove it like this for about 2 years. (it was an older guy so he didn't get on it or anything plus it was a weekend car)

Need your help guys.

3rdCoastPowerSports

iTrader: (5)

have you drained your oil and checked it for gold dust?

vladsvt

Oil has been changed, it looks pretty good just smelled like fuel (car runs abit rich needs a retune)

poltergeist 02

iTrader: (65)

no ticking or knocking?

86lxnotch

iTrader: (3)

bearings may have to much clearance......

vladsvt

Nope, I mean nothing irregular, there is some valvetrain noise and whatnot, but nothing out of the ordinary.

Does this require a rebuild? Or just use thicker oil?

poltergeist 02

iTrader: (65)

i thought the same but 5-6psi? sounds like something else to me. if there are no knocks or ticks i wonder if your oil psi sending unit is going bad. it's strange that your psi is normal on cold startup and then drops so drastically once warmed up.

3rdCoastPowerSports

iTrader: (5)

ive always noticed the oil pressure sending units go to 130 psi when they go bad... if its reading good oil pressure then drops to 5-6 psi you have an issue and if you actually have 5-6 psi then you are most likely damaging the motor. i believe the min oil pressure required to run properly is 8 psi. i would verify you oil pressure with a mechanical gauge

vladsvt

I'll try to look it up with a mech. gauge just to make sure, what doesn't make sense is the car have been driven for awhile like this with the problem and still does.

Could this be "walking" cam bearings or w/e there called? I got an email from the previous owner of the motor and he said that he switched the cams over

BTW The car also backfires above 4500rpm but I assume that's a different issue (still need to take care of it) But I only went WOT once since I bought the car

poltergeist 02

iTrader: (65)

if it was a bearing issue i would think that you would see some foreign material in the oil (metal flakes-shavings) it might be worth your time to check the o-ring on the sump tube that goes to the oil pump just to rule that out. kind of a lot of work to get to it though.

86lxnotch

iTrader: (3)

what oil is currently in it? thicker oil is only really a band-aid unless it was bult like that on purpose. usually with a bigger clearance a HV oil pump is also used to help fill the void. yes if it is a clearance issue best thing would be to rebuild it, i personally would have a reputable shop go through it and let them know from the get go about the issue that way they can look for the problem during teardown

remauto1187

iTrader: (1)

Did the new oil pump 3000 miles ago change anything?

ABQ99TA

iTrader: (17)

If your at 5-6 at idle your are eating bearings. Or something else is very wrong. Cut your filter and look to see if you have an issue. Good luck

Paul Bell

iTrader: (9)

Barbell?

ABQ99TA

iTrader: (17)

I don't think you would get any pressure with out the bar bell

JS01

iTrader: (10)

Cam plate or rear cover gasket could have a leak. Missing barbell or front galley plug would read lower than 5-6psi IMO, have seen engines ran before without them and they registered no oil PSI.

gMAG

iTrader: (1)

I had the same symptoms.
Initially, the used block with 31k miles would have 40-45lbs cold. After warming, it went to 28lbs.
Over time and a few high speed runs, warm would be 26, then 20.
As this happened, there was no evidence of chips or contamination in the oil or filter.
Finally, pressure dropped to 4-8lbs, then zero.
There were a whole load of chips in the oil at that point, and #'s 7, 4, & 2 rod bearings were shot.
As 3rd CoastPowerSports asked..."have you drained your oil and checked it for gold dust"
I learned that if you have gold dust in the oil or filter, the "gold" would be your cam bearings (they are brass colored), and if you have silver specks, this is evidence of rod or main bearings.

Paul Bell

iTrader: (9)

RE the barbell, there was an updated length of this component. Also, if the O-ring on it was damaged, it could cause issues.

chrisfrost

iTrader: (8)

What is the pressure like as You accelerate ,,,,,,,,does it stay lower than normal , or comes back up or ? You should for sure check with a mechanical gauge and change You're oil and inspect the old oil and drain and cut open the filter and inspect . I would'nt drive it any more until You figure out what is going on because it may sound like nothing is being damaged but can be damage occuring . Good luck

BTW in post #14 that distance should read .8 - 1.4 mm not .08 - 1.4 mm

vladsvt

Thanks for the responses guys!

Being that the mechanical gauge is out of question (my mechanic tested it and it reads almsot the same as the digital one), and new oil pump was installed, along with the sender, that only leaves one potential option, and that is loose clearances in the bearings and that makes sense now...


I talked to the previous owner of the motor and he said that they built the engine with very loose bearing clearance, here is his quote "main and rod bearing clearances were set very loose being it was a racing motor plus the oiling passages were opened up to allow more oil to flow up to the cylinder heads". I do not have the exact specs of how much is "loose" but I assume its not as big deal since the motor have been ran like this for 2-3 years with no issues other then it reading lower pressure.

Now my question is, if I put a high flow melling pump and alittle bit thicker oil will that be okay? Will it raise my pressure? Because right now I have a stock ported oil pump. Also does it require a rebuild? I mean I understand that its not "optimal" but the car has been running like it should for along time with no problems, (and it still does drove it to mechanic 1 hour we test drove it no weird noises nothing)