Maybe someone can shed some light on this for me...I know far more than most about cars but compared wtih some on this board I know practically nothing...I know that low oil pressure can be a sign of bad bearings I just responded to a post about it and it got me thinking...what exactly is going on with the bearings that cause the oil pressure to drop off?

 

My understanding is that the bearing clearances are out of specs.

 

Thats what I always assumed and it makes sense but I just never was sure.

 

As the clearances 'open up', the corresponding drop in the 'resistance to flow' causes oil pressure reduction.

 

Exactly, increased flow results in pressure loss.

 

but then why do pretty much all LT1s have low oil pressure? My 65k LT1 has about 15-20psi @ idle, around 40 w/ the pedal, just saw a beautiful 94 z28 m6 w/ 43k miles, same oil pressure, everyone I talk to has about the same pressure, so should I be worried about my bottom end, or is this normal? Right now I'm running valvoline 5w-30 full synthetic and napa gold oil filter.

my stock 97 s-10 w/ the 4.3 has 35-40 at idle and around 60 w/ the pedal, it's got 94k miles and has been over tached a couple of times w/ missed shifts.

I know lt1 clearances on the bottom end spec out the same as all 350s, but what about the pump? are they generally weak, or faulty pressure spring, or do the lt1s naturally open up over time?

 

My guage reads 18-22 at idle...I've read the dash unit reads high and I've read it is also low by a couple PSI if you're at 15 PSI I'd get it checked and see if your guage is off...15 psi is where I start to think a little...12 and I'm worried that the bearings are hosed or will be shortly...I drove my IROC around though for 15k miles on 6 PSI at idle...bad bearings, rod knock etc...my plan was to drop in a 350 LT1 or LS1 when it broke and it never did...I wound up selling it.

 

20psi at idle and 40psi at mnoderate rpm is normal for a SBC and therefore for an LT1. Not sure how the LS1's run, but my '01 Silverado runs a good 20psi higher than a traditonal small block, as they all do. Not sure why or what GM changed. I'd be interested to find out.

Rich Krause