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Anyone rebuilt their 6.5 or 6.2?

Discussion in '1982-Present GM Diesel' started by Steve_87K5, Mar 27, 2004.

  1. Steve_87K5

    Steve_87K5 1/2 ton status

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    I'm ready to start reassembly. The heads are rebuilt. Cyls honed, new cam bearings, rotating assy balanced (new coated pistons). Is port matching worth the extra work? Can I machine out an EGR intake to make a J-code equal? Any tips on short block reassembly and DB2 calibration appreciated.

    (I'm using the small chambers, 6.5 injectors, stock CR, DB2 mechanical pump, banks turbo, Peninsular water pump)
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    FWIW the amount of material I took out of my J-code manifold to match it up to the intake gasket was amazing. The gasket laid on the head showed the intake ports on the heads were cast much more accurately...

    On the intake itself there were some ports that had 1/4" or more of material down the width of the runner that got removed. The casting was about 25% smaller in area than the gasket opening on average.

    On the top side of a C-code intake you could remove all the ribbing and EGR stuff and just make it one big smooth entry point for the air. I don't have solid numbers for how much difference this actually makes but I felt a difference under my right foot. Total cost was a bit of my time and a carbide burr for my die grinder. I also used a small flap wheel to polish up the inlet 'bowl'.

    I figure it gets more air than it used to, and that was the point.

    Rene
     
  3. Steve_87K5

    Steve_87K5 1/2 ton status

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    Thats an amazing amount of material! I'll match the ports, but need a grinder. What brand of grinder did you use? Air powered? RPM ?

    On the stock J code manifold, is the center bowl free of any obstructions? I'm wondering If I can successfully mill out the C code. What do you think?. (I have a mill)
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I used an inexpensive air powered Die grinder made by Campbell Hausfeld. It uses a 1/4" collet and spins approx 20,000 rpm. The carbide burr I used is specifically made for aluminum and looks fairly agressive. It is no more than 1/2" diameter at the largest, then tapers down to a 3/16" diameter ball at the end. It gets in very tight quarters and did a fine job of the manifold.

    The J-code I have just has a wall in the inlet area that splits the manifold. I should have removed that wall altogether, but instead I knife edged the top of the wall and blended and polished the rest of the inlet area with a small flap wheel on the die grinder. A mill would make very short work of the inlet area on a C-code manifold.

    Seeing as the manifold on a diesel is dry I figured volume and velocity would best be improved by enlarging as much as practical and then polishing where I could. The less the air can 'grab' along it's path to the combustion chamber the quicker it should get there.

    Rene
     
  5. arveetek

    arveetek 1/2 ton status

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    The C code intakes are dual-plane, divided plenums. You'll have to remove an awful lot of material to open it up like a single-plane J code. Plus, you have the exhaust passages built into the intake that will be in your way. The J codes don't have that.

    It will be much simpler to replace the intake with a J code. The earlier J code are divided plenums, like Rene's. I have a later model that is an open plenum. It is completely open, with no dividers at all. Either one will flow much better than your stock C code intake.

    If nothing else, remove the EGR valve and drive a freeze-plug into the EGR opening to block it off. That's what I did until I got my J code.

    Casey
     
  6. Steve_87K5

    Steve_87K5 1/2 ton status

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    Casey, I agree, better to find a J code manifold than to modify a C.

    I have seen MIL Humvee manifolds forsale. How does the basic design of these intakes differ from the J code?

    Rene, thanks for the die grinder info!
     
  7. arveetek

    arveetek 1/2 ton status

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    The Hummer intakes are a direct bolt-on. However, the mounting bolts for the air cleaner are turned 90 degrees, so you'd have to drill new holes. Plus, the intake is shorter, so a spacer may be needed to properly fit the air cleaner or pressure chamber.

    There's a guy over at TDP who is running a Hummer intake with his Banks system. He had to do a little modifying to make it work, but no big deal, really.

    I would look for a regular J code intake first, but if you stumble across a Hummer intake, that would work to.

    Casey
     

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