L92 or l9h

[Sc0rp]

I tried to look before posting what is the real difference between a l92 and l9h 6.2 engine reason I ask is my 2009 denali shattered a piston and there is a $600 difference in the long block motors the l92 being cheaper and the only thing I can find is flex fuel being the difference between the cam and crank part numbers but the specs seem the same besides that but if flex fuel is the only difference that is a intake and fuel pump not the engine so please someone clarify this for me because I plan on buying a longblock and if I don't have to pay that extra 600 because there is no actual internal engine difference that money can go to my exhaust headers or programming and rear o2 delete (I am in Florida no emissions) and thank you in advance for the help ppl

 

[iamdub]

FlexFuel capability is really the only difference. Swap an L92 injector setup onto an L9H it'll be an L92. Swap an L9H injector setup onto an L92 and it'll be an L9H. In the earlier years, the L92 had AFM components but AFM wasn't activated. This is irrelevant to your '09, though. With just long blocks, I don't see the reason for the price difference unless they're including the intake manifold with the long block. Even then, it's just higher-volume injectors on the L9H.

 

[Sc0rp]

No intake, fuel rail, injectors or oil pan standard long block l92 or l9h but a 500 or so difference in the price of the long block was just making sure before I save me some money

 

[91RS]

The cam and phaser are different on the L9H. The L92 has more adjustment than the L9H and L94. I would get the right engine.

 

[14RamHemiSport]

I tried to look before posting what is the real difference between a l92 and l9h 6.2 engine reason I ask is my 2009 denali shattered a piston and there is a $600 difference in the long block motors the l92 being cheaper and the only thing I can find is flex fuel being the difference between the cam and crank part numbers but the specs seem the same besides that but if flex fuel is the only difference that is a intake and fuel pump not the engine so please someone clarify this for me because I plan on buying a longblock and if I don't have to pay that extra 600 because there is no actual internal engine difference that money can go to my exhaust headers or programming and rear o2 delete (I am in Florida no emissions) and thank you in advance for the help ppl

If you dont mind me asking, what caused the destruction? My 09 denali runs great but you now have her worried. I dont recall reading a lot about engine issues with these 6.2L trucks.

 

[Geotrash]

If you dont mind me asking, what caused the destruction? My 09 denali runs great but you now have her worried. I dont recall reading a lot about engine issues with these 6.2L trucks.

Don't know if he'll be back so I'll chime in. The most common cause is a dropped valve - usually a broken valve spring. It's the reason I'm doing a cam swap with a dual valve spring upgrade in my '12 and will also do it in my '07 if I like the results.

 

[14RamHemiSport]

Don't know if he'll be back so I'll chime in. The most common cause is a dropped valve - usually a broken valve spring. It's the reason I'm doing a cam swap with a dual valve spring upgrade in my '12 and will also do it in my '07 if I like the results.

appreciate the info....but what is the cause? these 09s do not have active afm so the whole cam/lifter issue associate with afm shouldnt apply.....correct? is it just bad luck causing the broken valve spring?

 

[Geotrash]

appreciate the info....but what is the cause? these 09s do not have active afm so the whole cam/lifter issue associate with afm shouldnt apply.....correct? is it just bad luck causing the broken valve spring?

Pretty much. A few guys here have experienced a broken valve spring in their 6.2s. The only root cause I can think of is poor metallurgy or QC. Poor metallurgy will lead to early fatigue failure, and a significant nick during manufacture can cause a stress riser point that leads to failure.

 

[14RamHemiSport]

Pretty much. A few guys here have experienced a broken valve spring in their 6.2s. The only root cause I can think of is poor metallurgy or QC. Poor metallurgy will lead to early fatigue failure, and a significant nick during manufacture can cause a stress riser point that leads to failure.

Maybe poor maintenance too? Pushing limits on an oil change interval is always asking for trouble. It's just not worth the risk. Either bite the bullet and change it early or do a few oil analyses to validate your longer intervals. Not all oils are created equal. Anyway....that's another subject altogether.

 

[wjburken]

Maybe poor maintenance too? Pushing limits on an oil change interval is always asking for trouble. It's just not worth the risk. Either bite the bullet and change it early or do a few oil analyses to validate your longer intervals. Not all oils are created equal. Anyway....that's another subject altogether.

I can attest that even with regular 3K-5K OCI using high quality synthetic oil I lost a valve spring on my non-AFM 2007 Denali at 140K. Fortunately it did not contact the piston. Unfortunately, at 150K a lifter roller grenaded and took out the motor.

 

[kbuskill]

I thought i remembered reading that the 6.2L suffers from valve float at higher RPMs.

 

[14RamHemiSport]

I thought i remembered reading that the 6.2L suffers from valve float at higher RPMs.

Any signs or symptoms to look out for? Im only at 104k miles. all stock. installed a catch can around 4k miles ago. very little highway. seems to run good so far.

 

[kbuskill]

Any signs or symptoms to look out for? Im only at 104k miles. all stock. installed a catch can around 4k miles ago. very little highway. seems to run good so far.

Not sure as I don't have a 6.2L, unfortunately.

 

[donjetman]

I race cars. I know about valve springs. They don't last forever. With miles they weaken and suffer from metal fatigue. The factory should lower the shift points via the computer as mileage grows.

 

[Sc0rp]

If you dont mind me asking, what caused the destruction? My 09 denali runs great but you now have her worried. I dont recall reading a lot about engine issues with these 6.2L trucks.

I am so sorry for taking so long to respond back but I did not drop a valve my piston came lose due to fatigue recently bought the truck and after my teardown I found minor shrinkage in another piston that the wrist pin skirt was cracking on probably due to the old owner overheating the engine more than once so I inherited there problem

 

[swathdiver]

I am so sorry for taking so long to respond back but I did not drop a valve my piston came lose due to fatigue recently bought the truck and after my teardown I found minor shrinkage in another piston that the wrist pin skirt was cracking on probably due to the old owner overheating the engine more than once so I inherited there problem

They probably kept refilling it with 87 instead of 91/93 octane fuel! 87 is a piston killer in a high compression engine.

 

[a4edwin]

They probably kept refilling it with 87 instead of 91/93 octane fuel! 87 is a piston killer in a high compression engine.

Was not aware of this.

 

[Geotrash]

Was not aware of this.

James is correct. Lots of folks just love to go on and on about how they've used 87 in their cars designed for premium fuel for years, with no ill effects. It's like smoking. You might get lucky, or you might not. Modern high compression engines use knock sensors to detect pre-ignition (pinging, in the old days), and retard the ignition timing to reduce it. But the system isn't perfect, and the engine will still experience transient internal cylinder pressures (ICPs) much higher than they would if being run on premium fuel - especially when used for towing or other high-output driving styles. Our engines use hypereutectic (high silicon) aluminum alloys for their pistons, which will accumulate fatigue over time, unlike forged steel. So when a high compression engine is run on lower octane fuel and experiences regular high ICP spikes, the pistons will eventually start showing signs of fatigue damage. My guess is that's what David is seeing the evidence of.