Most '' built'' motors go to a thicker oil such as 10w-40 that's what I run! Mine idles at 40# hot and 65-70# at wot! But I have the melling select 10355 pump

 

I was too, until I did it myself! Luckily I was using one of those little telescoping mirrors to see behind the oil pump pickup tube and saw a little bit of o-ring sicking out before I buttoned it up.

 

Pulled it out of an assorted box at work after I tore up the GM squarecut o-ring on the 3rd time removing the pump because of pressure loss. No idea what the part number is (I think it was an AC system o-ring), it is blue and like 2 regular o-rings joined by a slimmer band between. It's sort of like an X ring but it's in the shape of an 8
The measurements have this ring roughly 2mm taller than the GM ring.

 

What are you talking about? The oem seal is not square cut.....

 

It is square when you remove it from a 9 year old engine...

 

 

I was gonna say...

But you guys beat me to it. If you are pulling apart a LS engine, do yourself a big favor. DO NOT try to save three dollars and re-use this o-ring. They usually have flat sides when they come out, and they often leave some orange (or green) material in the bore if you look really close. That right there is an indication that the o-ring is no good.

 

Damn, and here I was thinking the OE ring normally looked like it came out of a garden hose.

I did finally figure out it was no good on the third attempt when I cut it and decided I had to have a new one.

 

Just to update everyone, the O ring was fine. When I put it in, the engine was upside down on an engine stand so I was pretty certain that it seated in OK. There was debris on the pump and tube from the old O ring. I am not sure if that contributed to the problem, but I cleaned the snot out of it anyways. While the pump was off I ported it, and installed a shim under the spring. When I had my machine work done the shop ordered my bearings for me. They weren't tri metal ones, and I installed them anyways just because there was so much success with stock bearings. Well after Richard chewed his up the other day I decided to get tri metal King bearings. I will plastigauge them when I install them. Hopefully everything together will boost up my idle pressure to around 40 PSI.

 

Here is what the debris from the old O ring looks like for those who haven't seen it. I used brake cleaner, and had to scrub it pretty good for it to come off.