Low oil pressure "new" Mast Motorsports LS3 427 - what next?

[Chad-1stGen]

As some folks know I picked up a Mast Motorsports LS3 427 a little over one year ago. I purchased the motor from the original owner who bought it in 2009 and never installed it.

Symptoms
When the motor is fired up it has great oil pressure which steadily drops as the oil heats up. When the engine first reaches coolant operating temperature it will still have 35+ PSI at idle and anything off idle is 50+ PSI up to about 65-70 PSI. However, once the motor is thoroughly heated up and engine oil hot, the idle pressure drops to 18-20 PSI and max oil pressure tops out at 35-40 PSI. If I sit there and keep the revs high (3500-4000) the pressure will drop abut 5 PSI as the oil gets really warm and idle as low as 14 PSI for a minute before coming back up about 5 PSI.

Is it really a new motor?
Some have questioned if it was really never installed but the motor was in the original crate pristine with no marks on the behll housing surface, Mast harness was not cut or crimped anywhere (some leads have to be hooked up) etc. so I'm confident I'm the first one to fire this motor since it left Mast.

Oil pan & pickup motor shipped with were swapped before first start
Before the motor was installed I removed the GM LH8 conversion pan that it shipped with and installed an Autokraft (champ) pan. So for a while I've been focused on it being an o-ring issue, pick up clearance, or soothing to do with the pan as that was the only thing touched after leaving Mast Motorsports. However, I've tried a new GM O-ring seal on the Autokraft pickup tube. No change. I also tried re installing the LH8 pan with pick up. No change.

Tried new oil pressure sending unit and gauge
I've verified that the sending unit for the oil pressure isn't the problem by trying a new sending unit and gauge. No change.

Mast confirmed that the oil pressure is lower than they expect.
They told me the oil pressure is lower than they expect and that when it left their factory it had 40-65 PSI from 2500 RPMs and up per the dyno. This is with ECT at operating temp. However, keep in mind it takes 5-10 minutes after reaching operating temps for the ECT before the oil pressure drops.

Oil type used:
Originally the motor was fired with whatever it shipped with. In the o-ring/oil pan chasing I've also used the Mast motorsports recommended 15-40 Rotella and currently has Valvoline Racing VR1 40w. This includes changing the oil filter. Both filters used have been AC Delco.

So now what?
Potential items to check.
Replace oil pump.
Check the clearances at the rods and mains
Check cam bearings?

I can change the oil pump but don't know how to check the other two items. What would you guys do? I'm temped to just pull the motor and take it to an LS specialist in SoCal if I can get a good recommendation.

Thanks guys.

[GregWeld]

Here's the drill.... and this is just me talking like we were buddies.


You're not going to be happy until you are really certain about what is up with the motor. There's only one way to find out... a "forensic" tear down.

There's nothing worse than stressin' over a motor you have questions about. As much as it hurts financially -- pull the motor and get it to a shop and have them tear into it and double check every spec. Anything less is a bandaid.

You're only going to be in it labor and a few 'small parts'... maybe a quick hone and re-ring.... if things are good. Let it go -- and you might be buying a block and crank and rods and on and on.

[Chad-1stGen]

I hear you Greg. I'm pretty much at that stage in my thinking but was speaking with a friend today and they suggested before taking that step to throw it up on here to see if anyone else had some ideas.

I'd also be interested if anyone knows of any shops specializing in LS motors or with significant LS experience in SoCal so if it comes to that I'm prepared.

[Sieg]

Have you asked Mast if they would do it and what they would charge? The time you spend researching local specialists then deliver and pick-up.........the difference might not be that much and you'd have confidence in the people repairing it.

[Ron in SoCal]

Chad check to see if the 'barbell' is there/installed properly. Also, it could've been run w a prior oiling probelm, so pull the pan and inspect a few main bearings.

If you need a forensic LS specialist, I gotta guy...

[intocarss]

Pull it out and apart ..fix it rt and be happy