Ok so i bought a shortblock LQ4 with 45k miles. This is my first time building an engine from a shortblock, well i bought a brand new GM oil pump for the build. I had a friend check the rod bearings and clearances and they all look good.. All the cam bearings looked good but the rear one looked a little worn out but went and put the cam in anyways. I checked the oil pick up tube with oil and it was clean.. So i had a o ring that was red but was faded green? So i put that in and when the engine was on the truck i went and started it up, the oil pressure went to 40 at idle and when the truck got to temperature it would drop down to around 20.. At that point i thought the oil pressure sensor was bad so i went and replaced it and still low.. wasn't convinced so i bought a manual gauge and it did the same thing. So i drained out the oil and it came out a little dirty, replaced with with rotella 15/40 oil with new filter hoping it would fix the problem.. still no. So i read on here that people were having trouble with green/blue O rings.. I got the GM part number to get the red one which is the good one. So i went and got it and it did look much thicker that the one i had put in, but i tried scraping it with my fingernail and the red would come off and under it was blue???? I put it in taking extra care that i wouldnt pinch it. So i did and again replaced the oil with the rotella 15/40 went and turned it back on and it would go to 40 and once it got to temperate it would drop to 20. I guess that did not fix the problem. The engine sounds very quiet at idle and works very good.. now im thinking what else would it be???? thanks for any help!!

 

Also at WOT its at 50, would i damage it more if i keep stepping on it with 5lb's of boost?

 

anyone have any imput on it?

 

50 psi sounds fine to me for WOT.. Have you checked the oil right after a wot pass. Does it look foamy?? Did you change to a diff style oil filter??

 

While I don�t feel like it is optimum, according to GM�s SI for a 2004 LQ4 6.0L (don't know what model yours is, but the info should be good), the Minimum Hot Oil Pressure is listed as:
6 psig at 1,000 engine RPM
18 psig at 2,000 engine RPM
24 psig at 4,000 engine RPM

I will say, as I�m sure you have heard as well is the old Hot Rod standard of 10 psig per 1,000 RPM is a good standard to go by.

 

Ill check it tomorrow after a WOT pass, when i used the rotella i put a new K&N oil filter in there. actually today i checked it at WOT and its actually around 40 (when cold it goes to around 60 WOT) The engine is a 04, thats very good information about the PSI per RPM! When it comes down to around 20 at idle the engine feels a little shaky.. so would i be ok upping the boost to around 9-10 lbs and still live a normal life??

EDIT: Also i have both valve cover vacuum hoses disconnected, would that matter?? one intake vacuum goes straight to the BOV btw.

 

if you used 15/40 oil after o ring replacement then naturally the oil pressure will be lower because its thinner(im sure u know this)... try wut the cap calls for.. 5/30 and oil pressure will def be atleast a little higher... maybe even enough to make you happy...


just my .02

 

??? 15w40 is NOT thinner than 5w30.

 

Have you done a leak down to ckeck the rings?

 

15/40 is alot thicker but didnt work. you mean a compression test? havn't thought about that, its not smoking at all nor missing oil but will try it today