Better Machining = Better efficiency
 

That link isn't working for me, its my computer.

During the 1940s tighter tollerances used at one of the GMs engine factories caused the old buick engines produced there to have roughly 20% more power and fuel economy than the same engine produced at the other engine plants.

When I put my diesel engine together I spent hours grinding out .018'' top, .014'' second and .015'' oil ring gaps on my engine, which is really pushing it on a turbo motor.
Tolarances on piston ring gaps like that will never come out of a GM, ford, dodge, honda, toyota, hyundai or kia factory.
Also floated the piston wrist pins with about a .001'' gap, as far as I know most pistons wrist pins are still push fit.
Then I went through 3 sets of main bearings to get the main bearing fit I was after.
Also ported the cylinder heads.

I saw a thumbs up on the thanks , figured close enough. I like your attitude :D

All I can say is wow, I wish I had the skills and patience to do that.

Did you balance the reciprocating assembly as well?

Engine frictional losses are an area of study for engineers for a long time now...
Japanese production motorcycle engines are all good example...
Crazy-high revs, very thin rings, next-to-nothing piston skirts, etc...

I remember reading an article years ago on building a production "stock" race engine...
How they measured and remeasured crank plain bearings to the "upper" tolerance for lower friction, mixed and matched parts to static balanced reciprocating assemblies (rules don't allow for removing material)...
The HP gains, and thus economy, we're substantial....

Have a look at this Ducati piston..
http://www.fastdates.com/PLN.NewBike....58Pistons.jpg

Small skirts where fore and aft load from the angle of the connecting rod push the piston against the cylinder wall...absolutely nothing on the sides where no load exists, save for the ring land area.
200 HP/liter specific output for production 4 stroke engines are practically common place anymore.
Amazing....

I dont understand the vodoo magic used to ballance the rods and pistons and I do not have the equipment to ballance the crank so I had a heavy duty diesel engine shop in virginia beach called "gregorys fleet supply" ballance the front pully, harmonic ballancer, crank, rods, pistons and flex plate for $260 if I remember right.

I also machined the heads for valve guide seals since the original 6.2L and 6.5 did not use any valve guide seals.
So now I have the only 6.5L that does not consume any oil.

I also went with low to very low tension oil rings:
Info: Low tension oil rings - Diesel Place : Chevrolet and GMC Diesel Truck Forums

I read the article finely...
It looks like they adapted race motor machining tricks to the production line.
Installing the mains and installing a torque plate with head gaskets in place of the cylinder head has been done for decades.

Heating the block for machinging is newer.

I have read that very well machined block will allow for the use of lower tension rings all around.

Now they machine the bare cool block and hope that torque and heat deform it to the correct shape.

NASCAR is the home of this kind of stuff for non-production building. Their engine builders not only have great materials, but know what works at insane levels of detail. Internal friction reduction is very expensive, but oh so worth it.

Especially for how many miles they go around on the track , the cost is minimal for the benefit.

The cost would also be minimal when applied to diesel engines that are usually run for at least 250k miles.