It's a Mellins LS6 oil pump. I was using Mobil 1 synthetic 5w-30. Will going to a 15w-40 help my PSI out at all? O-rings and everything was installed correctly. In the middle of a build now and wanted to know what you guys think before I button everything back up. Cold it idles around 50PSI but once it's hot it's around 25-30 and WOT is 40. Never heard anything out of the ordinary from the Valvetrain & etc. Basically a long story short. Is this normal & would heavier weight oil bring the oil PSI up?

http://www.youtube.com/watch?v=A2CtqEso0pA

 

I would first if u could get an aftermarket oil presure gauge or scan tool and see what the computer is seeing the oil pressure. These gauges are not super acurate.

 

after watching the video that is not normal oil pressure..... if the gauge is bad then ok but if not..... that is really bad oil pressure at the end it actually went down with higher rpm. I have the ported ls6 pump and at idle its a little below 40 and wot it almost gets up to 80

 

What weight oil are you guys running?

 

5w-30 non synthetic oil.... castrol GTX to be exact. However changing brands or from 10w-30 will make this big of a difference. u were below 40 psi at like 5 grand that is not normal

 

in the video on the second pull it looks like the oil pressure is bleeding off somewhere it drops then comes back up. def get a different guage on it first.... if it confirms stock gauge there is an issue

 

Wasn't going to mess with it but since i'm in the middle of a h/c swap i'll pull it off to make sure the o-rings and everything is still in tact.

 

The first number is the viscosity when the oil is cold and the second number is the viscosity when the oil is at operating temp. So going from 5w-30 to 10w-30 won't make any difference when the oil is at operating temp. If you want an oil that is thicker at operating temp you need to go with 5w-40 or 10w-40.

 

Schwanke Engines built the Short-block and recommended using 15w-40. Would that make any diffrence? Like "11seccamaro" said. I did have a slight surge in high RPM's.

 

Yes 15w-40 is thicker than any grade of 30 weight oil, and a Xw-50 oil is even thicker at operating temp.

 

So do u think that'll have anything to do with the high RPM slight drop/surge.

 

It's possible, you could switch to a 30 weight oil and see what happens. I do know that 5w-30 is the recommended oil for the LS motor, so it's worth a try to see if it eliminates the pressure drop.

 

If the engine builder is recommending a different (higher in this case) oil viscosity that should mean that the internal clearances have been set based on the use of a higher viscosity. Using a lower viscosity oil will result in lower oil pressure. That may not mean there is no other problem, but you should run whatever weight oil the builder designates.

 

Thats a mechinal issue. Unless the oil pressure sender is going bad. If was a built short block double check to see if the barbell or oil bypass was installed correctly. Oh and how much oil is in the car?

 

They didn't say anything about it until I called and asked myself for the OP being low.

 

Check it with a mechanical gauge cause it might be the sending unit.

 

Went with 20W50 on my new build and everything's perfect.

 

Hi.
The 20w50 oil should raise your pressures 10-20# depending on bearings/etc/.
I use the 20w50 conventional and keep things changed with a little lucas..
However, the other post suggested using an external gauge to monitor actual pressures. I would highly suggest doing this for peace of mind. Don't forget that a nick/etc. On oil pump o-ring can have adverse effect on pressures......good luck and keep us posted on your find........have a blessed week......captain jim

 

Erik recommended 15w-50 for my motor.....

 

15w-50 for mine too. Went ahead with the 20w-50 since it's easier to come by in my area.