L92 or l9h

[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.