Attention: TDR Forum Junkies 
Tuesdak
TDR MEMBER
I am well qualified to bash these engines so no further need to do so. They are throwaway engines that are still in production, due to military need, with no less than 2 re-designs to fix GM's bean counter problems. Cracking blocks at the mains, head cracking, miserable cooling in the 90's body style (Worse in the Hummers) cast cranks to please bean counters that fail if the damper on the engine fails...
Unlike a Cummins rebuild being near $10,000 I can get a low mile military surplus 6.2 longblock for around $2000, an improved Optimizer 6.5 military surplus for around $3500. A brand new improved 6.5 Optimizer longblock is $7250. Clearly it's more fun with the budget engine where the pain isn't so high when it goes "BOOM!".
It wasn't so much the continued lack of power from NA 6.2 engines as 6.5 turbo versions that still lacked power with the lack of fuel economy turbo'd that turned me to the darkside to see what you could really get out of these engines. Getting more power and going from 7.5 MPG to 10.4 MPG towing was a welcome surprise. In depth for those interested: http://www.maxxtorque.com/2012/07/the-65l-diesel-factory-equipped-asthma.html
More or less a huge turbo that doesn't light till 2000 RPM, 2400 stall RPM Yank converter, but limited fuel by running mostly maxed out 6.2 pumps that have smaller plungers than a 6.5 pump. I have a Moose Jr pump to run now. Still reaching for a bit of sanity because I could have cone with a much bigger Moose pump. It's now a fun truck. Stock 6.5TD's are a total dog and worse towing. 6.2NA's can't get out of their own way, period.
Bigger turbo:
Vid with a smoke free 6.2 pump:
Due to a SNAP emissions test where you floor it in park and hold the engine on the governor to measure smoke a total of 4 times on a good day, more if they have trouble, I had the privilege of watching my hot-rod 6.2 commit suicide when the IP governor failed and let the engine rev out to 4200 RPM way past it's 3600 RPM redline. Luck: it just bent valves and didn't blow up. Hindsight being 20/20 and all. I first replaced the IP and then the hi-pop injectors. Still wouldn't hardly accelerate. Advanced timing to get it to start and run till I could figure it out. Later A compression test showed that the valves were all hammered from overspeed.
Not so clear as to what is wrong:
You can hear some of the problem just cranking (electric fan in background to help AC):
Compression test, min 320.
1) 320 2) 260
3) 300 4) 200
5) 260 6) 260
7) 300 8) 260
Due to headstuds in wet holes sealed with RED threadlocker I pulled the engine to do head work. It's a 1993 so not that much hooked up to it. And I needed to change a bad engine mount ruined from biodiesel leaking on it.
On teardown:
Hammered exhaust valve tip
All 8 piston crowns have surface cracking (eroded glow plugs indicate too much timing).
Clear that a valve is tapping a piston:
And this is why, of course, the broken spring is on the high compression hole:
Further Uh-Ho on a cam lobe:
Cracked head - extends through the cracked valve seat:
Unlike a Cummins rebuild being near $10,000 I can get a low mile military surplus 6.2 longblock for around $2000, an improved Optimizer 6.5 military surplus for around $3500. A brand new improved 6.5 Optimizer longblock is $7250. Clearly it's more fun with the budget engine where the pain isn't so high when it goes "BOOM!".
It wasn't so much the continued lack of power from NA 6.2 engines as 6.5 turbo versions that still lacked power with the lack of fuel economy turbo'd that turned me to the darkside to see what you could really get out of these engines. Getting more power and going from 7.5 MPG to 10.4 MPG towing was a welcome surprise. In depth for those interested: http://www.maxxtorque.com/2012/07/the-65l-diesel-factory-equipped-asthma.html
More or less a huge turbo that doesn't light till 2000 RPM, 2400 stall RPM Yank converter, but limited fuel by running mostly maxed out 6.2 pumps that have smaller plungers than a 6.5 pump. I have a Moose Jr pump to run now. Still reaching for a bit of sanity because I could have cone with a much bigger Moose pump. It's now a fun truck. Stock 6.5TD's are a total dog and worse towing. 6.2NA's can't get out of their own way, period.
Bigger turbo:
Vid with a smoke free 6.2 pump:
Due to a SNAP emissions test where you floor it in park and hold the engine on the governor to measure smoke a total of 4 times on a good day, more if they have trouble, I had the privilege of watching my hot-rod 6.2 commit suicide when the IP governor failed and let the engine rev out to 4200 RPM way past it's 3600 RPM redline. Luck: it just bent valves and didn't blow up. Hindsight being 20/20 and all. I first replaced the IP and then the hi-pop injectors. Still wouldn't hardly accelerate. Advanced timing to get it to start and run till I could figure it out. Later A compression test showed that the valves were all hammered from overspeed.
Not so clear as to what is wrong:
You can hear some of the problem just cranking (electric fan in background to help AC):
Compression test, min 320.
1) 320 2) 260
3) 300 4) 200
5) 260 6) 260
7) 300 8) 260
Due to headstuds in wet holes sealed with RED threadlocker I pulled the engine to do head work. It's a 1993 so not that much hooked up to it. And I needed to change a bad engine mount ruined from biodiesel leaking on it.
On teardown:
Hammered exhaust valve tip
All 8 piston crowns have surface cracking (eroded glow plugs indicate too much timing).
Clear that a valve is tapping a piston:
And this is why, of course, the broken spring is on the high compression hole:
Further Uh-Ho on a cam lobe:
Cracked head - extends through the cracked valve seat:
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