6.2L VLOM options

[12GMCYukon]

I’ve got a 2012 GMC Yukon XL 1500 with the 6.2

I’m trying to reseal the VLOM, but no one sells the inner seals for the 6.2 like they do the 5.3

I have AFM tuned out but all the hardware still installed. Can I install a smooth VLOM or plug the oil passages without causing damage or engine issues?

 

[Charlie207]

I don't think I'd plug those passages unless the entire AFM system has been physically replaced with non-AFM parts. It would be fine as long as AFM never turned back on, but seems a little sketchy.

You can certainly swap in a smooth valley pan cover, and have the option to go back to the VLOM if you sell the car.

 

[12GMCYukon]

So the smooth valley pan, with the o-rings but not the oil passages, will work without issues? Like the ACDelco 12598832 @Charlie207

 

[Charlie207]

So the smooth valley pan, with the o-rings but not the oil passages, will work without issues? Like the ACDelco 12598832 @Charlie207

Yeah, just install whatever the non-AFM engine uses.

 

[rdezs]

In "theory" I think you will be fine with that flat valley cover.

My theory is based on the oil flow. It appears the oil is supplied through the channel past the sending unit after it goes through the screen under the sending unit. That supplies oil to the solenoids in the vlom.

So it looks like the solenoids have two functions. In 8 cylinder mode, you have oil pressure coming up the towers from the lifter bores, and the solenoids keep those closed off to maintain the pressure in the lifter bore.

Switch to 4 cylinder mode, the solenoids open to bleed off the oil pressure from those lifters by opening the channel that comes up through the towers, effectively collapsing those lifters and preventing the valve from opening. (There's a large spring on top of each AFM lifter that keeps the slack out of the system and prevent a tapping noise, as well as keeping a downward pressure on the lifter when a bleed down is required for 4 cylinder mode)

Back to V8 mode, the solenoids close again, using the oil pressure being supplied them through the channel that goes past the sending unit to overcome the inherent lower pressure coming up the tower.

In basic terms I see the solenoids as an electromagnetic switch, assisted by differences in oil pressure on each side of it.

My only end result question, and I regret not inspecting VLOMs I have removed in the past for this specific thing.... Is, 'where exactly does the VLOM release the excess oil during a lifter bleed down?"

I have noticed clean areas on the underside of a high mileage VLOM.... Assuming it was a pressure leak in the system, but perhaps those are points where it releases oil?

The large round orange seals are what's over the towers. Clean inside for the most part from oil flow. It's the surrounding areas that are clean that raise the question. Note the small hole in between the two round sealed areas. That good in fact be where the excess oil drains. This example had AFM turned off approximately 40,000 miles before the delete.

So I would say with a certain degree of confidence that if you use the valley cover with the o-rings, you can even tap metal plugs into the towers for extra measure, there will be no method to bleed off the AFM lifters and they will have a constant supply of oil pressure to keep them pumped up.

On the subject of the large springs on the top of the AFM lifters.... I wonder how many failures are more related to those springs. They press against the underside of the plastic lifter tray. If there's a failure there and it goes into 4 cylinder mode, you're likely to lose a push rod off a rocker arm, and have a lifter bouncing off the camshaft.

All this combined is one very good reason to absolutely delete the AFM hardware as soon as you can.

AFM lifter in the below pic on top, non afm lifter is the lower one

And here's a photo of the bottom of a lifter at around 175,000 miles. Actually looks really good, all were identical. The engine had regular oil changes at no more than 5,000 miles.

 

[Charlie207]

 

[rdezs]

View attachment 462132

Lol, because when working on something complicated it's a good idea to know what's going on. Would you want someone working on your engine, not knowing the details of why something needs to be done? I guess some people don't care, they just pay the bill without questioning....

 

[mikez71]

I have noticed clean areas on the underside of a high mileage VLOM.... Assuming it was a pressure leak in the system, but perhaps those are points where it releases oil?

Around the 7:20 mark he says that is the bleed hole, and that there is another type out there.
He likes to cut that surrounding gasket so there is no chance of oil leak building up pressure somehow.. I think was the gist of it..

 

[j91z28d1]

please do not install a flat plate or plug the oil towers with afm lifters installed. the afm lifter will unlock and get stuck. you could cut the gaskets around the towers to vent the pressure but why.



just use the 5.3 gasket, or just black rtv, non ultra, I found found anything Permatex sells that says ultra is soft crap. old school black silicone Rtv or Honda bond is about the only thing oil resistance these days. even thou it's hell to clean up afterwards haha.

 

[j91z28d1]

In "theory" I think you will be fine with that flat valley cover.

My theory is based on the oil flow. It appears the oil is supplied through the channel past the sending unit after it goes through the screen under the sending unit. That supplies oil to the solenoids in the vlom.

So it looks like the solenoids have two functions. In 8 cylinder mode, you have oil pressure coming up the towers from the lifter bores, and the solenoids keep those closed off to maintain the pressure in the lifter bore.

Switch to 4 cylinder mode, the solenoids open to bleed off the oil pressure from those lifters by opening the channel that comes up through the towers, effectively collapsing those lifters and preventing the valve from opening. (There's a large spring on top of each AFM lifter that keeps the slack out of the system and prevent a tapping noise, as well as keeping a downward pressure on the lifter when a bleed down is required for 4 cylinder mode)

Back to V8 mode, the solenoids close again, using the oil pressure being supplied them through the channel that goes past the sending unit to overcome the inherent lower pressure coming up the tower.

In basic terms I see the solenoids as an electromagnetic switch, assisted by differences in oil pressure on each side of it.

My only end result question, and I regret not inspecting VLOMs I have removed in the past for this specific thing.... Is, 'where exactly does the VLOM release the excess oil during a lifter bleed down?"

I have noticed clean areas on the underside of a high mileage VLOM.... Assuming it was a pressure leak in the system, but perhaps those are points where it releases oil?

The large round orange seals are what's over the towers. Clean inside for the most part from oil flow. It's the surrounding areas that are clean that raise the question. Note the small hole in between the two round sealed areas. That good in fact be where the excess oil drains. This example had AFM turned off approximately 40,000 miles before the delete.
View attachment 462118
View attachment 462119

So I would say with a certain degree of confidence that if you use the valley cover with the o-rings, you can even tap metal plugs into the towers for extra measure, there will be no method to bleed off the AFM lifters and they will have a constant supply of oil pressure to keep them pumped up.

On the subject of the large springs on the top of the AFM lifters.... I wonder how many failures are more related to those springs. They press against the underside of the plastic lifter tray. If there's a failure there and it goes into 4 cylinder mode, you're likely to lose a push rod off a rocker arm, and have a lifter bouncing off the camshaft.

All this combined is one very good reason to absolutely delete the AFM hardware as soon as you can.

AFM lifter in the below pic on top, non afm lifter is the lower one

View attachment 462120


And here's a photo of the bottom of a lifter at around 175,000 miles. Actually looks really good, all were identical. The engine had regular oil changes at no more than 5,000 miles. View attachment 462121

I only read the first part but this is not how afm lifters are released. you have it backwards. the oil passageway is pressurized and oil goes thru an extra hole in the afm lifter, this moves the pins and then when the cam lobe lifts the lifter it collapses instead of lifting the valve. once the vlom solenoid closes, the pressure is vented and the internal pinps spring back to lock the internal lifter, the top spring stabilizers the push rod when on the base lobe and the lifter locks. afm lifters default is locked. it take pressure to unlock them.

this is a different internal oil passageway than the normal hydraulic plunger in the lifter that gets oil from the normal passageway that runs thru the middle of the lifter bores, but the lifters do have clearance inside so that everything can move, and oil pressure will get around from the normal hydraulic lifter side and make it's way up the afm activation port, if this pressure isn't vented it will build up and release the pins and let the lifter collapse when not commanded. this is why when you do the bypass mod, you not only block off the oil passage under the pressure sensor to keep oil from going to the vlom solenoids you much also cut the gaskets around the afm towers, this makes sure that even if sludge builds up, the pressure can still vent making sure the lifters do not activate.


edit if you want to test this, like in the crazed performance video, you can put compressed air into the afm oil port to release the pins and compress the lifter by hand.

 

[rdezs]

Lol, then that confirms that the best plan of attack is to get rid of all the AFM hardware

 

[j91z28d1]

Lol, then that confirms that the best plan of attack is to get rid of all the AFM hardware

technically yes, but 2k plus for a diy kit, pulling heads and half the engine apart plus all the while you're in there isn't really worth it to 95% of the people. throw in your tranny is probably on its last leg too if it's not been addressed already and you're well over the cost of the truck. most shops won't even do a delete these days and if they do you can't trust them. so it's a new engine for you.


I work on stuff for a living and honestly I have no desire to pull a good running engine apart, it's a hard pill to swollow, in my cause even worse being a hybrid no one seems to have completed a delete and it run right afterwards. while we may have just got to the bottom of this, as a another hybrid guy had a timing chain thrown off, (I guess it's a Gen 4 ls thing) he replaced the chain, gears/vvt and tensioner with standard stuff, only for it to miss like crazy and bearly run. Come to find out the hybrid 6.0 has a different part number vvt setup, so the cam timing was off. if guys that tried the delete using the standard kits and wouldn't run right that's probably why. but not sure what is the correct combination of parts yet.

so again, there's many reasons why doing a full delete on a old 2000s truck isn't worth it to a lot of people and a 20$ block off kit and turn off on the tune is not a horrible idea, then just drive it till it's ready for the junk yard. now that said, everything new is junk too these days and horribly over priced. so I will personally try and fix mine. but only when it breaks haha. it's got 170k on it. if it makes 250k before the valve train gives up, that might be long enough for me to consider just buying something else and parting out the truck and keeping the aluminum 6.0 as a ls2 build for something else.

 

[rdezs]

Well, it could be done for well under $2,000.... And that's with a lot of replacing items just because you're in there. (Water pump, belts and hoses, thermostat, all sending units.) You do far better on price by sourcing individual parts, plus you get better quality.

On a 2014 Escalade that is spotless, no rust at all, 172,000 miles.... Worth somewhere around $12,000..... For well under $2,000, AFM deleted, heads gone through, L92 OEM camshaft, LS7 lifters, new timing set with upper and lower gears, VVT solenoid and actuator, new oil pump, cylinder head gone through and flat valley pan, with all sensors replaced and belts and hoses.... Definitely worth the investment to keep driving it till the wheels fall off. Transmission is original, but it's always had an inline hydraulic spin on filter and fluid changed at 25 to 30,000 miles. She commutes in it 50 miles round trip, on a 55 mph State highway.... Not much stop and go in it's life.I

The price of the AFM delete, as well as all the preventative maintenance I do on the vehicle, is extremely cheap compared to the price of a new vehicle.

 

[rdezs]

Lol, last year she still had the original brakes, hubs, front brake pads we're at about 30%. So here's what preventative maintenance looks like, and the whole thing was cheaper than having a shop simply do the brakes: