600hp Build - GK or MK Block? Detroit Series 60 12.7

The leak in front by head may be due to the lack of a support bracket they added around 2000. It supports the front structure. Upper left (drivers) side. Bottom leaking may be from the front and rear structures also. Along with main seals.

 

My late 99 MK has oil coolers, basically the same as BK, but different injectors. I have it at 550/1950.

I remember reading that without oil nozzles it's not recommended going above 500

 

Can you show a pic of that bracket? I don't think I have it and it might be a good idea to get one

 

No picture. It’s located above the compressor, behind the air intake tube. Elbow corner bracket. Maybe 10” high, 8” wide. Bolts onto block just below the head, and into the upper rear portion of the inner front structure. My 99 didn’t have it. A friends 2000 was recalled and installed under warranty. My current 2000 has it. It’s a different blue color, than the engine green.

 

Here it is @DUNE-T


Big bracket goes left side of head to front cover. The small bracket goes on the pass side top of head to front cover, and replaces a small L bracket that was used there

 

From my research all the MK engines started to have oil nozzles starting in the 2nd half of 99, so yes, mine are factory, checked by serial number.
My factoring tune was 430hp, even though on the engine label it says 470hp.
The truck was a turd, never got above 6.5mpg.
Now it's amazing, with light loads I get to 8mpg and pulling power is great.
I had a tune from Leon, did not like it, truck was black smoking like crazy. Switched to Fernando's from DCS and really happy with it. Tried 702 turbo also, but switched to k31

 

Not claiming to be an expert but from my experience and digging here are my thoughts.
1. If you are going to spend the money on an out of frame, and want 550 to 650 hp, go with a block with piston coolers. 500hp is the limit without piston coolers. I think if you get a BK kit you will get the correct rods too.
2. Turbo wise, 1702 works great for 600-650hp depending on your gear ratio and your transmission.
A K31 might be a better choice if you are not running heavy.
Let me explain.
If you want higher hp but want milage too. You are probably looking at a 13 or 18 speed with double OD. This means your cruising rpms are going to be low. My experience is a 1702 doesn't spool very fast at 1150 rpms. A K31 will spool faster at a1150 rpms.
Now if you have a 10 speed and same hearing you will probably be at 1250 rpms as an example and the 1702 will spool quicker.
Realize 1702s are big enough to provide lots of boost on 15 liter motors.
3. Mpg is a more complex configuration than most guys want to think about.
Are you running light?. 80k? 100+?, empty some?
What tire size 24.5s or 22.5s?
Great Ratio? 390s 355s 323s
Your mph range 50 to 75?
Transmission 10, 13, 15 or auto?
Flat ground, hills, or mountains?

All of this is needed to factor in when when getting your rpms around 1300 so that when you roll your foot, the engine fuels and spools fast and you don't just smoke and choke till you get into the "power range".
There are lots of good shops that can build you what you ask for in a motor as far as hp goes.
If you are going to spend the money on an out of frame 100% new engine make sure it matches the rest of your truck and your hauling needs.
If you want more info I would be glad to talk to you.
I like 12.7s. It just seems sometimes folks want the results of a 14.7 or a 15 liter out of a 12.7 and are disappointed after spending 40k on a rebuild.

 

I’m disappointed in the 702. Engines dead under 1300 rpm. Should have gotten the k31