Finally getting back into the rebuild. I had a issue with oil pressure being dead low at idle(and operating temps)... Took to machine shop for the second time, but keep getting the run-around about how it's busy and they still have had no time to look. Initially last year they replaced my cam bearings, got new rod and main bearings, was line honed, had one rod replaced (out of tolerance?), New rings, and got a fresh cylinder hone. Crank was rotated/whatever they do with it also. Prior to this I never had any issues with my oil pressure. I'm going through threads and was wondering .. do the gen 3 LS1 5.7 have a oil screen before the OPSU? Can't find any information but it seems to be a common item to for the gen 3/4 blocks.. unfortunately I don't have the block to verify but I do not recall reinstalling one when I put the new block plugs and barbell in.

 

You didn't forget to install the barbell behind the rear cover when you got it back from the machine shop?

ETA: I now see where you did replace the barbell sorry.

 

Its okay, yeah I replaced it just in case the old one was worn... Besides the rotating assembly and the block, everything is brand new in that engine lol

 

Other places to look is a stuck oil pump bypass valve and if the correct o-ring was installed on the oil pickup tube. An old camshaft retainer plate if the orange gasket has been mashed flat through the years can lose pressure from the oil galleys... but probably not enough to have zero oil pressure. Did you take off the valve covers and get a visual of oiling to the rockers?

 

Tried two different oil pumps, new retainer plate. Didn't check under valve cover, pressure was about 45ish cold, but hot/idle was too low

 

What is hot idle pressure? What is hot 2k rpm pressure? What oil weight?

 

Machine shop said to run stock weight oil (5w30). At hot idle it was down to 14, when I revved it to 2k rpm, it went up to a about 20-25ish. As the rpm ame down with each rev the oil pressure wanted to keep dropping, I have a video of it with a wet gauge hooked up to it, I don't know exactly how to post it on here though

 

That sounds almost like a pickup O-ring issue. Like the thin O-ring was used where it needed to be the thick one, or the O-ring itself got damaged or something, or the pickup isn't seated right in the pump.

 

I think the one we were using was the red o ring... It's thicker than the black one that we tried that came with the pump. Installed the o-ring with the engine out of the car and did it again with the engine in the car, I swear I'm becoming a guru at pulling these motors out of these cars since this is like my fourth time. I found if you use a small flathead to poke it as it slides in, it helps make sure that the ring stays even and doesn't end up getting pinched out the side of the pickup tube as you're sliding the tube in the hole. I did not tighten the tube down as means to draw in the tube to the pump, only after it was seated. there's a new pickup tube in there also.

 

I don't know too much about the colors of the O-rings; to me that seems like an easy way to go down the rabbit hole and end up taking a world detour.

The pickup that's either necked down right above the clamp flange, or that has the "flared" or "tapered" feature, should use the thickest O-ring. I think most of them are like that, and for all I know all the replacement ones are as well. There's about a .030" or .040" difference between the place the O-ring goes and the end of the tube, on either of these types; so the O-ring needs to be about half that much thicker. The kind that's straight uses the thinner O-ring. Personally, I've never actually come across one that needs the thinner O-ring in my own stumblings, but my experience is somewhat limited.

Use the thickest one that will fit without major force. Another thing that might be helpful in this area is one of these. https://www.saccitycorvette.com/OilTubeHoldDown.html

 

Melling o-ring instructionsAttachment 713563

 

The first time I tried, I replaced it with a red o ring, but after viewing the sheet again/looking up the fbody part, it's a blur o ring, that gets replaced with the black one

 

Use a heavier weight oil

 

Is it common to have to run a heavier oil after I rebuild?

 

Not if rebuilt correctly. All clearances should be the same.

 

Agree. DO NOT use heavier oil. FIX THE CAR, not hack-job around it to fake the gauge into reading less wrong.

Don't trust the O-ring colors, go by measurements.

 

I think at this point I'm just going to go pick up my engine and start tearing into it again myself. Wasted enough time with them, would hate for them to push me out until January and find out I'm having the same issues. Is there any vendors that do rebuilds on customer supplied blocks? Seems most have blocks you buy outrightl

 

What brand of 5w30 are you using?? May be your problem - consider running a different brand.

 

Running valvoline conventional. They said that would be fine for it. They explained no synthetic oils are to be used during the break in period/until the rings are seated

 

Good advice on the break’in

I run Rotella t6 full synthetic 5-40 Which says right on the jug to compare with 15-40 of other brands. Rotella t6 full synthetic 5-40 Is sold as a heavy duty Diesel engine oil - why do I use this?? Previous owner used it was recommended by shop that upgraded my engine.

You May be chasing your tail -