Ok background of the motor is it is a 94 with 61k. I began running Valvoline synthetic blend 10w30. Cold oil pressure is 40-50 psi at ide and 10-20psi warm idle. Crusing doesn't see over 35psi when warm. The major problem comes at WOT. Oil pressure will be around 35-40 but as soon as it hits 5000-5500 rpms, the oil pressure dips to about 20psi or so. I replaced the sending unit and removed the oil cooler and started running 10w40, but I actually noticed a slight pressure drop using 10w40 over 10w30 at idle. I can't decide if the problem is bearing failure or the oil pump going south. Any help is appreciated.

 

anyone?

 

Maybe the hard acceleration is leaving the pickup uncovered? Does it do the same thing in Park? Meaning...rev the car in the driveway and watch the oil pressure. Does it still only give you 20 psi at 5k rpms?

 

Josh has a point.Also,what kind of filter are you using?

 

Guys I'm having the same problem. No one on here will be able to tell you what it is, because no one knows. There are a few people that have this problem My car has about 50psi cold at idle with 0w40 mobil 1. It has about 15 psi at hot idle. At 1500 rpms hot it gets around 30 psi. When I romp on it in second gear pulls the pressure will go up to 50psi, drop down to around 30, then spike back up again. I have seen as much as 60psi at redline(6200rpm) before though.

I have noticed this happening for a while, and haven't blown anything. I have raced the car every once in a while so it hasn't been pampered. I say don't worry about it.

John

 

I'm using a 3/4 quart ac delco oil filter. I forget the model number. I removed the oil cooler thinking that might be the culprit. I installed an aftermarket oil pressure guage over the oil filter, and that gives a better oil pressure reading, although it still dips at WOT. I don't think its an acceleration problem because at WOT in first gear, the car just sits there and spins the tires, so its not exactly pulling.
FastZin, my problem is basically like yours. I know someone else that had a simmilar problem and he said he fixed it by installing a high pressure oil pump and a windage tray and baffle so I might try that next.

 

A high pressure pump? I have a high volume pump in the garage, but to be honest with you I just don't feel like putting it on.

I don't know, I think I'm just gonna leave mine like it is.

 

i have the same problem.

i use 10-30 valvoline oil. i have a 93Z with 118k miles. i would go from a death stop or slow roll and the oil pressure will go up to 55psi than drop back down to 30 than back up after it shifted into 2nd gear. i was leaking oil from everywhere at the time. so i pulled the motor and replaced all the gaskets, pan, intake, rear main, front cover..... and i replace the oil pump with a high pressure oil pump.
put everything back together and i had no more oil leaks. before i had 20oil psi warm and 35psi when cold. and about 55-60psi at WOT. after the oil pump still using 10-30 i now saw 25psi at idle warm, and 70psi warm WOT. i stomp on it from a stop and the oil pressure went up to 70 and then drop down to 50psi. i still had a problem but i thought 50psi isnt too bad.
after a while my tires got hard and bald, and my rear diff cluthes took a dump and i only had one tire spinning. I no longer had the oil pressure drop problem. but then i fixed the rear and bought some drag radials and immiately on the first punch the problem returned. it would drop from 70psi to 40-50psi. so I used some Lucas oil additive and i see 35-40psi at idle and up to 75-80psi at WOT. thou the problem is still there. it still drops to 45-50psi. when the car hooks really good.
this only happens in 1st gear too.

i didnt have the problem when the car just spunned bad, i only have it when the car hooks good.

i say ive had this problem for about 8 months or so, the car is still running good. so i think its the bearings. i dont think the oil pressure drops if i stomp on it in 1st when the car is cold.hmm i will have to test that again.

 

I have two '94 z-28's one with 26K miles the other with 30k. The one with 26K recently dropped oil pressure 15-20psi at idle hot and about 40-45 above 2500-3000rpm. The other car idles at 35psi hot and 55-60psi above 2500-3000rpm. I over reved the one with lower oil prssure due to a missed gear down shift and suspect some bearing damage may have resulted unless the oil pump is malfunctioning. I use 10-30 valvoline. The facotory manual states the minimum oil pressure is 6psi hot at idle and 24psi at about 2500rpm. That sounds pretty low to me. When the Minnesota snow starts to fly I will drop the pan and inspect the bearing condition, plastigage clearance and replace the pump. Has any one else found the pump to be the culprit?

 

i have never heard of an oil pump going bad.

 

i have never heard of an oil pump going bad.

 

This was discussed years ago on the f-body email list. For some odd reason the oil pump can cavitate on the Lt1 after cam upgrade. Can't remember if it was Summit or Jeg's who sells the Moroso anti-cav oil pump to fix this. Strange but true.
Doug

 

my heads have never been unbolted and i have never replace my cam.

 

My car was doing it before any internal engine work.

 

Because of where the Oil sending unit is mounted on the top at back of block it's far enough away from the oil pump to where you have more oil pressure than the gauge is reading, The only way to get an accurate reading is to put a sending unit down by the oil filter. Just my .02