earthman01

I was at the Glen Monday with my C5Z running a fresh LS2 402. Near the end of the second session I noticed my oil pressure dropping and pitted immediately fearing I was loosing oil. A thorough inspection found no leaks, so I sought the advice of other Vette owners. The consensus was that I had not added enough oil and I was experiencing the well-known LS2/3 oil pick-up problem. I restarted the car after it had been sitting for a while and had normal oil pressure, so I added oil and went out on the track again. After 2 or 3 laps the pressure started to drop and I came in when it was nearing 20 psi. After another huddle it was suggested that I go to 15-50 wt. versus 10-30. I did that and had good pressure for the first few laps, then started loosing 5 psi per lap. I put the car on the trailer and came home. I'm stumped, any ideas???

95jersey

After a hot session, I have seen pressure's drop into the high teens at idle in the paddock. Once car cools down, the pressure goes right back up like you describe. I am trying to remember, but when the oil was that hot, even when I revved the motor it only went up into the high 20's low 30's.

97C5inSD

what are the oil temps that you are seeing? if there not over 200+ then you may have other issues otherwise the above mention 95 jersey is about on also

Sherminator

Any engine oil cooler on the car? Any idea on what the oil temps were when pressure was low? What kinda oil pump are you running?

waddisme

Was 20 as low as it got? If it was running hot, 275* or above, 20 psi sounds about right even with extra quart. I think David Farmer said 20 -25 was not bad. My LS2 with cooler still runs around 275* but stays at 30 -35 psi. I keep my DIC on oil temp so I can keep an eye on it. May not be as bad as it sounds. I am running the 20-50 Amsoil if that matters.

Rob's 73

Do you know your bearing clearances?

AlwaysInBoost

I see 260's MAX with a cooler and 15x50 M1 on my forged 346. I do it the other way around, I keep my DIC on coolant and check oil temps on the straights. highest coolant temps I remember seeing are mid 230's. IIRC the oil pressure is around mid 20s @ idle when I'm pitting in.

C66 Racing

Was the 20 psi you were seeing at track rpm or idle? If track rpm, and unless your oil was over 300F, I think you have mechanical problems. This is somewhat confirmed by your 5 psi drop per lap with 15w50.

My fear is that you have partially wiped a bearing. If you have not drained the oil yet, I would recommend picking up a sample bottle from Blackstone Labs and submitting the oil for analysis. If you have high levels of wear, the analysis will show it much better than an oil pan or filter inspection will (unless you have already broken something which it doesn't sound like).

If you don't have high wear, then the problem could be in the oil pumping system.

Personally, I would not run this engine over idle until you figure this out.

C66 Racing

I'd say those are hot idle pressures right after the session, not while out on the track and I can't tell from the OPs comments where he saw the 20 psi.

FYI, for comparision, I'm now running AMSOIL Dominator Synthetic 10w30 Racing Motor Oil (Product Code RD30QT), a high ZDDP oil that doesn't meet GM Standard 4718M, with a DRM aluminum racing radiator and an external oil cooler. At VIR a few weekends ago in ambient temps that were around 80F, my coolant temp was about 210-220F and oil temps (which I watch on the DIC) were around 248-257F and oil pressure on the track of about 50 psi. If my oil temps go up into the 260s, I might go up to a 40 grade oil.

earthman01

I do run an oil cooler and oil temps are usually in the 250-270 range. The 20 psi readings were on the track, not in the garage. I will get the oil analysis done before I do anything else. Thanks for the info guys.

96CollectorSport

If the analysis comes back clean I would look at the oil pump, if the o-ring around the oil pump is cut or not sealing you would bleed the oil back into the oil pan. Hotter thinner oil would cause it to bleed by faster.
Just another thought.