Low oil pressure on new rebuild

[MNcarbturbo]

I had posted this on the B4black page but I thought Id post it here to get a few more ideas. I have a 3.8 carbed turbo I just rebuilt (ya, I know Im wierd ) It got new .040 pistons 20/10 ground crank, ect. Normal rebuild stuff. I did Earl Browns timing cover mods, and installed a high volume melling pump kit. Put the motor together and stuck it in the car. Runs fine but there is low oil pressure. Its only like 2-3 at idle and 8 or so when it gets up in the RPMs a little more. There is flow so its not like the pump isnt spinning. Took the turbo oil line off and it came out at a good flow.

The thought was that the pressure releif plunger was stuck halfway out so it let all the pressre out. I pulled the pump cover off and changed the pressure to 70 from the 60 PSI one I stuck in origially. the plunger didnt come out easy but it was pushed all the way down so that idea is thrown out.

Any ideas why I have such low oil pressure on a motor that has had almost all the rotating parts replaced/ground except the cam? Kinda makes me mad that I did all the oiling upgradeds out there and I still have oil problems. Is there something that can cause this? Id rather not take this motor out of the car again.

 

[49-blues]

Bearing clearances-viscosoty of oil? It should read about 10 psi for every 1000 rpms that the motor is spinning.

 

[Lee Thompson]

?

You said YOU rebuilt the eng. What bearing clearance do you have--Rods and Mains. Did you prelube the eng? Did you use expansion plugs or pipe plugs in the front?

 

[thadeal4real]

low oil

sounds like u might have a plug out it happens?

 

[MNcarbturbo]

The crank was ground and according to the berring package the berings were to spec so Dad who has rebuilt engines before thought it wasn't really needed to check the bering clearences. This was my first real rebuild so i didnt really argue and it made sense to me. Plus the chance of getting the wrong parts with the box saying the right spec isnt very likely.

I did prelube the engine and it made the drill work so it was deffinitly pumping oil.

Theres a chance that a plug came out somewhere or didnt get put in. I know theres 2 little screw in ones for the back of the block along with 2 bigger plugs and the rear cam plug. So from what I understand there is some soft plug holes in the front of the block? I dont remember seeing any holes for plugs in the front. I know there is 2 small soft plugs that I didnt use and thought they were just spare stuff in the kit.

 

[Robert Wilson]

Here is where the plugs go Lee is talking about

 

[turbodave231]

Well,

You made a mistake by not checking bearing clearances. Never, Ever trust that everthing is OK when assembling an engine. Check everything!!!! I've found many machining mistakes by checking/measuring before final assembly

Good measuring equipment is expensive and important when assembling an engine. That's why professionals charge the prices they do. Plastigage is fairly cheap and easy to use and will give you some idea if the clearances are close.

You may have blown out one of the two front cup plugs. I always tap these holes and install shallow pipe plugs to be sure they never let go. Even if that turns out to be your problem, go back and at least plastigage your bearings. I'd hate to see you go through the effort to correct the plug issue only to find lower than expected oil pressure later on. These engines need tight bearing clearances or they end up with poor oil pressure. I'd be shooting for .0015- .0018 on the rods and .0018- .0022 on the mains. In my experience, Buick V6's seem to like these tolerances.

Sounds like you'll need to remove the engine and find the problem.

 

[MNcarbturbo]

Well thanks for the help guys! Have to pull the timing cover off and see if I forgot those plugs. The plan is to get some head work done on this motor and a new cam soon so Ill have to pull the motor back out once I have more patience for this project again.

 

[GSTOY]

Never assume anything....check all clearances. People make mistakes putting things in boxes, and with mass production, clearences do vary.

Steve

 

[ryan319]

not to beat a dead horse but we went through 3 sets of bearings that "should" have worked until we a mismatched set that gave us the correct clearances. and this was with a new std/std crank.

 

[pajo]

bearings

""" Dad who has rebuilt engines before thought it wasn't really needed to check the bering clearences"""---say what ? you dont check them once but twice and three times but hey look at the bright side ,we learn something every day I imagine you are not going to forget to check them next time -- good luck ..

 

[MNcarbturbo]

Ya, It was a mistake to not check the clearences. Have to deffinitly check them first time next engine I build. Good news is The soft plugs in the front near the cam never got put in. Didnt notice it till I stuck the guage on it. At least it isnt a huge fix. Covers already off. Another 2 hrs and it should be running again.

 

[novaderrik]

what kind of a gauge are you using?
a cheap gauge might give an improper reading.

 

[Blown&Injected]

Plasti-gauge works VERY GOOD - - I bet it is a galley plug

 

[MNcarbturbo]

No worries anymore. The 2 front plugs right next to the cam were missing, they are in and it has good oil pressure now.