Tried it all, I need help. A constant Oil pressure fight.

[Collinmcballin]

Hi all. Collin here. I kinda feel like a theif lurking on these forums for years. It's my time to chime in and hopefully help/and get some help. No idea how this works but gotta start somewhere.
I have a 2005 Tahoe. Great truck, awesome condition. 251k miles, trans never been touched lol. I take really good care of it and it's not hot rod'ed

I've been fighting an oil pressure dilemma for a year and a half. I've used this forum, knowledge, videos, everything. Still can't win.
Standard 5.3 lm7, just rebuilt top end after dramatic water pump failure and those stupid 706 crack-tech (castech) heads cracking.
Ported 243 heads, ls6 springs, melling cam. Pass CA Smog, no tune. That's a conversation for another time. No CEL, The engine is quite fresh, still leaks like a siv who cares. Wicked torque.
I've always tried to fix my low/dropping oil pressure. The only way to get it back up is to change the oil. Ready to hear what I've already done...? (besides heads, cam, lifters, rockers, etc. She's clean on the inside and well maintained)
-oil pan, and gasket (de-sludged it)
-oil cooler block gasket
-melling 295 pump
-pick up tube and o ring (obviously)
-PCV system re-route to avoid consumption
-crank and cam sensor o-rings (common leak)
-Cam gear, chain
-Cam retaining plate
-sending unit along with that stupid NON EXISTENT screen everyone talks about HAHA
Literally everything. Help.

*Truck loses oil pressure, especially after light off roading or going up to mountains (heat?) 10psi
*Rattles on cold/sitting a while startup and takes 10 seconds to build pressure (and up to 30sec after an oil change)
*it will hold 45psi hot/idle for the first couple days after oil change
*valvetrain rattling when the pressure goes down NOT A SENDING UNIT DON'T GIVE ME THAT JUNK
*I KNOW the truck has good oil pressure in there somewhere, it truly runs awesome when I'm not getting whipped by oil pressure dilemmas
*checked with Guage everything is accurate

I feel like I've literally done everything and I'm losing hope. So much time put into it. Such a great truck!

Adding an oil cooler next week, for preventive care
Gtx 10-30
I've had the motor basically apart and got rid of as much sludge as possible. That was last year

SHEESH that was a long one.
Thanks guys

 

[rockola1971]

Did you freshen up the block? New Cam, Rod and main bearings? Replace dog bone? Missing dog bone?

 

[Collinmcballin]

16.5avg yup.
Great vehicle

 

[Collinmcballin]

Did you freshen up the block? New Cam, Rod and main bearings? Replace dog bone? Missing dog bone?

I didn't have the motor out completely. It was basically down to long block in the hood haha. The work I've done has been over the course of last 1.5 years.
Bearings looked good. No dog bone because motor is still in.
BUT Wouldn't that result in no oil pressure at all..?

 

[swathdiver]

Have you changed brands of oil filters too?

My money is on worn bearings, cam bearings specifically.

Take a weekend on put new rings and bearings in the motor, sounds like you are young, healthy and knowledgeable enough to make this an easy peasy job!

 

[rockola1971]

I didn't have the motor out completely. It was basically down to long block in the hood haha. The work I've done has been over the course of last 1.5 years.
Bearings looked good. No dog bone because motor is still in.
BUT Wouldn't that result in no oil pressure at all..?

Not likely the dogbone (left out) since you didnt take block down to rebuild fully. I suspect cam bearings is your problem if you replaced oil pump to fix the problem and the problem still existed after new pump install. I know the pressure wouldnt be right if the dogbone was missing. Ive never forgotten one so I didnt get that Tshirt.

 

[Collinmcballin]

Have you changed brands of oil filters too?

My money is on worn bearings, cam bearings specifically.

Take a weekend on put new rings and bearings in the motor, sounds like you are young, healthy and knowledgeable enough to make this an easy peasy job!

Yes, I use only ac Delco but have used microguard in the past, been a few years in ac Delco.
I started using the pf61 as it's a taller filter, trying to protect this high milage beast haha.
I really appreciate it! I have some really good friends that would help me do that. Seems like a lot of extra tools. Eesh.

The weird part is that it can hold great oil pressure for even a few weeks after an oil change, then starts to drop. And when I go off roading it'll plummet and start rattling. Shut off for 15 min then I'm good, only goes back to 20psi..

 

[Collinmcballin]

Not likely the dogbone (left out) since you didnt take block down to rebuild fully. I suspect cam bearings is your problem if you replaced oil pump to fix the problem and the problem still existed after new pump install. I know the pressure wouldnt be right if the dogbone was missing. Ive never forgotten one so I didnt get that Tshirt.

The sound of cam bearing scares me... Pull the block and take it somewhere? Or do it at home? *frantically Google searching in the background*
Honestly the pressure was excellent for a few months after the new pump. So weird.

 

[rockola1971]

The sound of cam bearing scares me... Pull the block and take it somewhere? Or do it at home? *frantically Google searching in the background*
Honestly the pressure was excellent for a few months after the new pump. So weird.

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

 

[Collinmcballin]

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

Sh

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

Yeah no kidding haha. This last weekend was the lowest I've ever seen it. Never seen it below 20 except a hot day pushing it hard.
I just happen to stumble across the "oil pressure bypass/releif valve"? Little spring loaded pin where the filter mounts... Some guys are blocling/plugging it... Never seen it before hmm..