Dingö

Hi guys, this'll be my first post and sadly still having some problems. I have a 2007 GMC Envoy Denali, and the Denalis have a LH6 LS. Thought that would be like a badass little tahoe, and I'm not really wrong. I really like it actually.

But anyways, I had lifter tick right after getting the suv. Decided to do an AFM delete and have a tech I know who works at a Chevy dealership do the work for me. I got all the parts for that delete, and gave him the keys.

Once he started tearing into it, he noticed shiny material. He told me about it, and showed me the oil pan and there was cam bearing material everywhere. Like chunks. We pulled the engine. And he said when taking it apart, the connecting rod caps were off on the torque. Some came loose super easy apparently, while others were very tight. The crank is newer aswell, which really had my tech confused.

So basically on top of the AFM delete (aswell as pretty much all the gaskets) , I bought new cam bearings, connecting rod bearings and bolts, melling oil pump, new water pump, new belts, piston rings, and also had him hone the block. He also cleaned the crap out of everything trying to get all the bearing material out. He said it was cranking smooth and looked good before he put it in.

Everything is now back together, and honestly runs great. Had another tech delete the AFM codes in the ecm and he also did some things for throttle response and fuel delivery. It runs really well. But as soon as the engine gets warmed up, the pressure drops off. It gets about 35 to 40 on cold start, and it has gotten as low as 5 (according to scanner) after driving for a while and checking it. As soon as I step on the gas, it'll go back up but only to like 20-30. I have the CEL for low oil pressure. Even changed the sensor, didn't do anything.

From what I've researched, I think the most likely cause is either the oil pan o-ring, or some stuck debris in the inlet, screen or something. But would like to hear others opinions aswell. Because I'm really trying to get this done with and have good pressure.

G Atsma

My vote goes to pickup O-ring...

tech@WS6store

iTrader: (2)

They will show low oil pressure "normally" when doing that unless you take the bypass out of the oil pan and also plug or use the lingenfelter rivets for the afm towers.

G Atsma

^^^^^^^^ Learned something here! Forgot about the DOD oil pan bypass.....

Dingö

What kind of bypass in the pan? Also I didn't know about riveting the towers, thanks for letting me know about that. You think I'll notice a difference with just the rivets, as long as it isn't the o-ring in the pan?

Dingö

Thanks for the replys tho guys, useful information. Also do you guys know if the lingenfelter rivets will work with a regular rivet gun? It seems pretty standard, but didn't know if it was "special" or something.

G Atsma

The rivets are a safeguard; The O-rings in the valley cover do a fairly good job sealing the towers. Call Lingenfelter about the rivet gun.

Dingö

I planned on doing that tomorrow to make sure before I order. But what about the oil bypass? Like the pressure relief valve? Because my tech told me after he got it off that there wasn't one, for whatever reason. Also, how would you suggest blocking it?

tech@WS6store

iTrader: (2)

There has to be one. its inside in the very back. its a pressure relief valve.
The rivets have a large pin so most guns wont do it.

Looks like this

Dingö

Does every AFM/DOD engine have a relief valve? Because 2007 was like the first year of the era, maybe early ones didnt? Or maybe the previous owners removed it, idk the engine has been torn into before and slapped together sketchy basically.

My tech seems to think its the oil pump. But I thought I got a high volume one, its a melling 10355 from autozone. Unless it is defective or something.

Its just that once its warm, it only gets about 10 psi per 1000 RPM. And it stays that way from driving around and watching my scanner pressure. Cold is fine, it starts right at about 40. But it slowly drops off, aswell as any power.

tech@WS6store

iTrader: (2)

Do not use high volume. period. use 10295. you deleted the need for extra volume with the dod delete.
All nnbs i have seen have that plug.
Put in the rivets. they only require valley cover removal. thats all.

Dingö

I'm going to order the rivets tomorrow. I guess we'll see if thats a reason for it. At least its something I needed to do anyway to do the delete properly.

Jscm3

The LH6 didn't have this in Trailblazer/Envoy/Rainier/9-7x.

tech@WS6store

iTrader: (2)

Thats a completely different oil pan setup.
I believe their bypass is in the top of the oil filter tube transfer assy. its been a while since ive done an oil change on one to look at the filter mounting area to see if its in the lower filter flange part like the obs stuff. if it is SACCITY Vettes makes a plug for it.

Dingö

​​​​​​
So I'll be able to see if it is or not by removing the filter like in this video?

Bypass Removal

Jscm3

MY_2K_Z

iTrader: (1)

I bet the pressure relief in the pump is stuck. I've seen 2 of them get stuck in under 100 miles and destroy the bearings. I prefer a shimmed ported stock pump over a Mellon.

G Atsma

Melling pumps are actually an upgrade over the GM ones

MY_2K_Z

iTrader: (1)

Ya I know that they are supposed to be but they are very cheaply made loose tolerance pumps in my opinion. If you take a stock pump and disassemble it and inpect it then take apart a Melling you will understand. And again I've personally seen 2 of them destroy a motor do to the pressure relief piston getting **** eyed in the bore and getting stuck causing oil pressure to drop to zero. Yet all of my stock, ported and shimmed pumps never seem to fail. Do some research on the melling pumps sticking and you will find hundreds of reports of the same issue.

G Atsma

If they were as bad as you say, the very reputable shops that sell them would quit doing so right here and now. Melling pumps have a reputation that was earned thru dependability and longevity. You had 2 fail on you. Unfortunate! Bad luck of the draw! It happens. But, that is not the norm, as I explained above. If you were to port and shim a Melling it would perform as good, or better than the GM ones you did. What you did was improve the OEM pump to better than the Melling std. production unit.