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I'll look over the pick up tube. I haven't inspected it that close. As far as the o ring goes I've used GM, and aftermarket ones. Blue, black, and red. It's definitely not an o ring issue. I've installed them on the engine stand with no angle at all. Impossible to mess it up that way.
The colors indicate a different size
Found this on another thread
They are color coded for a reason if the pickup tube has a recessed area where the o-ring goes you need the thicker RED o-ring. The trucks use this design.
With it being a corvette, the "correct" o ring is the blue. Which I used the with the first and second oil pump new from the dealership. Once I pulled it apart the third time I threw in the thicker red one. Thanks for the ideas but it's not an o ring problem
What O-ring did you use on the pickup? Felpro only makes 1 version of the O-ring and it's kinda in the middle of the two that GM makes. It might be OK for the pickups that require the thinner O-ring, but will cause problems for pickups designed for the thicker one. Make sure it's Green for a Melling pump or blue for a GM pump.
In my case, the pickup appeared to be designed for the thinner O-ring, but we had to use the thick green Melling O-ring to fix the low oil pressure issue. Very difficult to get on without damage.
OK... Read more, sorry. I didn't think my issue was O-ring related. Convinced it wasn't. But it was. Are you CERTAIN you have the right O-ring and more importantly, are you certain that you didn't damage it when you installed it. They can be exceptionally difficult to install
I never did try the huge green one. I installed blue with both oil pumps. Then I tried a thicker red one with the stock oil pump. Which was a very tight fit. I did try a 20-50 oil for about 20 miles. Oil pressure would ride around 18 hot. I felt it was masking the issue and not solving it. Rear galley plug is installed I assumed this was the problem and pulled the motor the first time
Have you ported any of the oil holes? Push rods have 3/8" inside diameter oil path (slight exaggeration)? If the block or heads were worked your machine guy could have opened up some passages that would reduce pressure.
Is the pressure relief, and the two plugs installed in the oil filter housing? Running an aftermarket oil cooler? Would require more fluid if that was the case.
Once again, have you tried an aftermarket hi pressure pump? I'm not talking high volume, not the same. No insults meant by any questions, just ideas floating around.
Yes, the Melling is a high pressure melling unit. It has the stronger spring installed. I also put that spring in the stock Ls6 oil pump with no improvement. I have done the o ring at least 4 times and swapped oil pumps twice, and springs twice. I'm getting ready to just drop it off at the machine shop again.
It's a manual 6 speed car. No aftermarket oil cooler installed. Only a turbo feed line. It has a restricted orifice so it doesn't rob much oil. I even blocked it off and started it with no improvement.
20.7 psia is 6psig.. that's just atmospheric pressured (14.7) added to gauge pressure. Both readings are the same. Not sure where you were going with that post.
Josh, another thought is that the pick up tube could be bent a bit so it is not submerged like it should be. You start up with full pressure, but once the oil level drops a bit, you only get the oil dripping back from the engine.
If you had pickup or o ring troubles the lifters would be clattering badly. Honestly if you are that determined to resolve this(as I would be too) I'd pull the engine down and find the trouble.
^good idea^ before it goes to the machine shop measure the crank journals and the ID of the bearings. More than .0015-.002 clearance can cause low oil pressure. You need clearance for the oil film, but there is such thing as too much. Let us know...
Ya know the rear cover could be leaking internally too or possibly oil passage damage some place. If you covered all the basics then you need to start looking for odd ball stuff.
