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  1. #1

    Block replacement - machining requirements? Engine Builder input needed.

    2006 GTX Standard 155HP NA:

    My block is junk and I need a different one.

    1) If I buy a new block, can I just assemble the engine and avoid dealing with the machine shops? I have 2 good standard sized pistons from my broken engine so I would need a 3rd. I think my rods and crank are OK - I will have them checked before I buy a block. I will be using new bearings and rings. I am assuming that I will need to plastigage at a minimum? Would re-using my 2 used pistons in a brand new block be a bad idea?

    2) If I go with a used bare block can I reuse the bottome half of my block with someone elses top? What kind of machine work will I have to plan to have done? I will bank on needing to bore the cylinders in which case I need 3 new pistons.

    Of course I could always by a reman engine, but I don't learn as much doing that and I am trying to be as low cost as possible.

    Thanks,
    Greg


  2. #2

    Join Date
    Jun 2010
    Location
    Toledo, Ohio
    Posts
    199
    +1
    2
    I think mis-matching the top and bottom of the block is not a good idea. In the automotive world they are machined as a pair, this is probably no different.

  3. #3
    I assumed the same, but wanted to find out for sure.

  4. #4
    A few points and questions:

    1.When you say "new block", do you mean brand new block or used? If new, you will not need any machine work. If you mean a good used block, then what it needs will be dependent on block condition. At a minimum, you will need to deglaze hone the block with a 400 grit ball hone, which you can do yourself at at cost of about $75 for the ball hone, but many shops only charge you about that for deglazing, and they can check your piston clearance at the same time.

    2. I personally will not reuse a rod if it was in a cylinder that had extreme damage to the piston. The forces in the cylinder from dropped valves, hydrolocking, and other stuff can slightly bend the rod and you will not have the means to detect it.

    3. I used to use plastigage for rebuilding/blueprinting automotive engines, but I will not use it on these engines. There is nothing you can do if it is out of spec, so I don't want to know, I would only worry about it if it wasn't exactly right, LOL.

    4. Per the other poster, don't use mis-matched case halves; they are machined as a set.

  5. #5

    Join Date
    Sep 2007
    Location
    Lexington, Ky
    Posts
    1,656
    Funny because its true...

    3. I used to use plastigage for rebuilding/blueprinting automotive engines, but I will not use it on these engines. There is nothing you can do if it is out of spec, so I don't want to know...
    Haha, I got a good chuckle out of that because your so right. Not much you can do if the bottom end is out of spec, so I'd just assume not know

  6. #6
    Quote Originally Posted by Sea Dood View Post
    A few points and questions:

    1.When you say "new block", do you mean brand new block or used? If new, you will not need any machine work. If you mean a good used block, then what it needs will be dependent on block condition. At a minimum, you will need to deglaze hone the block with a 400 grit ball hone, which you can do yourself at at cost of about $75 for the ball hone, but many shops only charge you about that for deglazing, and they can check your piston clearance at the same time.

    2. I personally will not reuse a rod if it was in a cylinder that had extreme damage to the piston. The forces in the cylinder from dropped valves, hydrolocking, and other stuff can slightly bend the rod and you will not have the means to detect it.

    3. I used to use plastigage for rebuilding/blueprinting automotive engines, but I will not use it on these engines. There is nothing you can do if it is out of spec, so I don't want to know, I would only worry about it if it wasn't exactly right, LOL.

    4. Per the other poster, don't use mis-matched case halves; they are machined as a set.
    Awesome information - exactly what I was looking for. As for the platigage, I figured you are supposed to know the clearances/tolerances, but what the heck are you going to do about it. That is good - one less thing to worry about I guess. When I said new I meant brand new. I figured if I had to do a bunch of machining to a used block I would be beter off with a new block, but it sounds like boring would be about the most aggressive I would have to go.

    Any other insight anyone?

    Thanks,
    Greg

  7. #7
    Quote Originally Posted by Sea Dood View Post
    A few points and questions:

    2. I personally will not reuse a rod if it was in a cylinder that had extreme damage to the piston. The forces in the cylinder from dropped valves, hydrolocking, and other stuff can slightly bend the rod and you will not have the means to detect it.
    How about re-using the crank when it has seen MAJOR damage in a cyl/piston? The crank looks good, no chips are marks that I can see and the journals all look good. However, I do not have a trained eye for such reviews. Should I give it to machine shop to evaluate and polish? Other recommendations? Also can a machine shop do testing on the rod, or is it just not worth it/

    Thanks,
    Greg

  8. #8
    Anyone know where there is a used block for sale?

    Thanks,
    Greg

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