Hello all,

Looking for some advise for my project. Issue is low oil pressure, which is also making some lower-end noises at idle which sound like rod knock. Idle at operating temp is ~17psi, cruise around 30psi at 2k rpm. I will be adding a blower to the setup in the near future, so want to get this resolved. This is a street toy and not a drag or race car. Should I upgrade the relief spring or return to the high volume/standard pressure pump originally on the engine?

Background:
'14 L77 from a Caprice PPV with 139k, which was silk smooth at idle and known good, though I never thought to check the oil pressure before being pulled. It has a cam swap with ls7 lifters and dual valve springs, and all bearings checked out good, and used the holley 302-1 pan setup for the swap. I deleted the DoD by putting plugs in the oil towers and deactivated it with hptuners. In doing so, I was also recommended to go to a standard M295 pump since the extra volume is not needed, which I ordered new and installed. I completed the swap, did a dual crank pulley pins for future blower needs, and proceeded to tuning. Over the next 10 or so heat cycle and driving sessions, I noticed that the oil pressure when at temp at idle was slowly going down from ~20psi on the first cycle to ~15psi on the most recent cycle, idle rpm set to 850rpm. This was accompanied by what sounded like rod knock, which did not happen at cruise, only idle when pressure was this low.

I freaked out, jacked the engine up, replaced the pickup and oring at the pump, and even went ahead and replaced the rod bearings as well. They were now worse than they were before, but by no means scored or bad. I refilled with the 10w-30 and same result...still around 16psi at idle. I added half quart of oil stabilizer, but the added viscosity did didn’t help much…maybe 18psi now. Went to 10w-40 and no real change.

The biggest concern I have is when coming to a stop, logs show rpm drops momentarily to 550rpm, which causes the oil pressure to drop as low as 5psi. I understand this rpm drop is causing the psi drop and correcting it with proper tuning would prevent this extreme low pressure. Just have not been able to resolve that tuning with limited experience.

As I understand it, the M295 is standard volume and has a 20lb relief spring. The stock high volume pump for this engine with DoD, the M365, is both higher volume and has a 30lb spring.

Hence the question…should I even try replacing the M295 spring for a 30lb or 40lb spring and see if it helps? Or is this more a question of volume from the pump and loose tolerances from the miles on the engine? Is there a way to tell it’s a volume vs spring issue? I am told that these aluminum blocks can wear at the lifter bores, causing high clearances and robing volume from the oil galley, and the easiest way to fix it is go to the high volume M365 and be done with it.

The spring would be a few hrs work to try, and may not be effective, but the M365 install would be a days effort, plus the joy of trying to align the crank and pulley correctly to allow the pins to be installed.

Thoughts? Spring or high volume pump? Any way to tell it is a volume question and not spring?

~Ryan
Charleston, SC

 

Spring won't help. Either your bearing clearances are fairly wide or you need to run a thicker oil... or move to a bigger volume pump. I think a 10296 would be good if you can get 6+ quarts in there.

 

How did your align the pump and crank “gear”? How did you prime the pump before starting it? If you didn’t do it correctly, You might of caused damage.

beat of luck
Jim

 

I tired the thicker using 10w30 with stabaliser, and 10w40 with no real change...2 psi or something. I have some 20w50 to try, but really dont want to keep going through $50 in oil for nothing.

My pan does hold 6 quarts total.

From the melling site:
The 10296 is a 1.14 cuin/rev and 43psi spring.
The M295 is 0.96cuin/rev and 20psi spring that i have on it now.
The M365 being considering is 1.28cuin/rev and a 33psi spring, which is the stock L77 pump.

So to me its a question of which I need...volume or pressure...or at least a way to determine it without sinking a weekend into troubleshooting.

~Ryan
Charleston, SC

 

I followed the video from melling on youtube....loosly mount the pump with two bolts, rotate the crank so the housing is centered, then tighten the 4 bolts to spec. I primed by pulling the oil galley plug, filling with oil that way, then using the starter with the spark plugs removed until it gets pressure. At the time, cold, it will build up 30psi and its turning at ~200rpm.

~Ryan
Charleston, SC

 

Pressure is determined by pump volume and bearing clearance. Throw the idea that the spring has anything to do with pressure out the window. That's a relief spring to control maximum pump PSI... but not the minimum.

If your pressure is down, you need more pump volume. But the question is why? It was a DOD engine to start with and their clearances may be a little wider than non-DOD pumps to allow for the larger volume pump to work properly. I don't know, I haven't looked at them. But I would say at least the 10296 is what you need. Or even the 10355 since that was the DOD pump.

 

got it. I was of the understanding that with the 20psi spring, that means that it is starting to open when the pump is at 20psi, and since that spring is located at the start of the system closest to the pump, but the pressure sensor is after the cam and lifters, that the valve may be opening already but the volume is being release prior to the sensor.

eithe way, sounds like i need to up the pump then. unless i am missing something furher.

~Ryan
Charleston, SC

 

I've never dealt with a DOD engine but I think it has a special valley cover with oil galleys, and the cover must be changed out for LS2 or LS3 or you'll end up with oiling problems.

 

My guess is at low rpm you are not getting the minimum flow you need for either the bearings or to worry the relief valve. I would put the DOD stock pump on.

Also, do you know that you know that you did not punch the pickup tube o ring?

 

OR even PINCH the O-ring?? Gotcha Darth... couldn't resist... lol

 

He's reinstalled it twice. I figure it's probably okay. Also, pinched o-ring usually shows 0 psi...

 

Lol. Facepalm

 

ya, its good...no pinch, punch, poke, pops, or cuts in the orings...definitly getting a good seal.

~Ryan
Charleston, SC

 

ya, by plugging the towers as i did, there is no longer any oil making its way to the valley cover and mechanical/hydrolic DoD system. the plugs are rated to something like 3kpsi, but i'll probibly pull the valley cover just to confirm the plugs are holding well.

~Ryan
Charleston, SC

 

How did you plug the towers? What did you use?

 

Did you measure your bearing clearances or your pan to pickup clearance?

 

its just an aluminum blind rivit...had to buy a pack of 50 though to use 8. pm me if you would like a set.

 

no i did not measure the bearing clearances...i checked the surfaces and moved on. So i assume the clearances are on the large side of spec. No, i have no way to measure them, nor interest in pulling the motor and rebuilding it at this time. it ran well before the DoD delete and swapping from the stock oil pump to the M295.

i did not confirm the pickup to pan clearance...the pickup is supplied by holley with their pan, so i assumed it was to spec. will confirm when i have the pan off again for the pump change.

 

Not real sure about your method of blocking the towers. I believe there is a DOD delete valley cover that seals those. You might look into adding that.
The L99 short block I bought was so equipped.

If any of those rivets is leaking.....

Ron

 

Always doubt your equipment as well until it proves otherwise. What are you using to read pressure, and from where? Have you tried another gauge? I know you said lower end noise, but we just went through this with a Snap On compression test gauge. Nearly guaranteed to be correct, and it wasn't. Almost pulled and rebuilt an engine that didn't need it. Gauge was way off as compared to 2 others that read identical (leak-down measurement is a better way to go, but still).

What about the "barbell", assuming no change, any leaks from that area? Some engines have up to 3 different oil pressure relief valves at various locations. One could be stuck open.

I would not think 15psi could cause a rod knock at idle. I did have an engine with gradually reducing oil pressure. There was dirt in the main bearings during assembly, from using an open tub of general assembly lube. That will never happen again.

Try a different filter? I did have a Fram fuel filter become un-glued from the end of the can, float to the other can end, and block off flow, yet only when flow was required. Damn near the hardest thing to diagnose, ever, that I have.

I have 240,000 miles on the 5.3L LH8 in my Colorado, and no oil pressure light or woes yet, runs perfect, and I stand on it every single day. I would not think 139,000 miles is shot by any measure, unless abused.