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Thread: How big a bore is too big?

  1. #11
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    He had the boring bar set for .040 on the top hole, to clean it all out, so.... Bored all three of them, the moron, and without bothering to call me first. I had to buy two more .040 pistons for nothing and have three .030 that are non-returnable.

    Thanks for the inputs.

    Jeff

    PS: Anyone looking for a set of brand new .030 pistons for in-line sixes?
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  2. #12
    Team Member zul8tr's Avatar
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    Next time get a different machinist. Started at +40 with the bar, not good.
    When I had + 15 over bore work done on my 25ss with my great machinist in Orlando, who is expert with 40 years doing blind bores, he gets the final boring max diameter by measuring the piston diameter at the correct skirt position and adds 2 x the desired wall clearance (.006 total = .003 wall). Then bores with 3 passes of the bore bar and the last pass was a bit less than desired max bore diameter, the final diameter was further machined with a special bore finish tool then honed for final wall finish.
    " Three may keep a secret if two of them are dead" Ben Franklin

    Location: SW Orlando, Fl

  3. #13
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    ..."Next time get a different machinist."

    You said it! That fool cost me hundreds of dollars.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  4. #14
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    The saga continues....

    Bought two more .040 pistons for the build then ordered new rings from Wiseco, but they sent me the wrong ones!

    Augh!

    Jeff

    PS: It's been my observation that a project that starts off wrong and gets all kinda screwed up turns out very well in the end. Hope so!
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  5. #15
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    I thought my problems with this bore job was over--NOT!!

    Assembled the crank, rods and pistons into the block, then turn it over. CLUNK! The # 2 (center piston) locked up solid before hitting TDC. Rotated the crank the opposite direction and same thing. "Doofus," I cursed myself, thinking a needle bearing must have dropped into the cylinder but no.

    Pulled the whole damn thing apart again, removed the rings of # 2 piston (to make it easier), and dropped the crank back in. CLUNK! What the hell?

    Eyeballing down the bore I found that, not only was the cylinder bored offset 5 to 10 thousands, the boring bar didn't go down far enough and the piston was hitting the ridge left behind. (Running .040 over slugs in what was a stock bore.)

    I slipped an old rod with a stock piston attached (no rings), masking taped it to fit snuggly, ground away some aluminum along the top, and it runs through TDC without a problem. So...

    No freakin' way am I gonna like that butcher touch my stuff again, and I can't see letting someone to bore the cylinder deeper without messing the wall up, so I'm going to clearance my brand new Wiseco piston so it doesn't hit.

    So how's your day going!

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  6. #16
    Team Member zul8tr's Avatar
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    Jeff
    Yikes! will there be enough clearance when hot at 6000 rpm with some rod stretch?

    The 5 to 10 offset why? He obviously didn't center the boring bar to the cylinder what a jerk.

    "I slipped an old rod with a stock piston attached (no rings), masking taped it to fit snuggly, ground away some aluminum along the top, and it runs through TDC without a problem. So..."

    Not sure what you did, Are you saying he left an alum ridge in the combustion chamber at 40 over and you ground that away?

    Better times to come.

    Pete
    " Three may keep a secret if two of them are dead" Ben Franklin

    Location: SW Orlando, Fl

  7. #17
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    I have been hearing boring stuff up for 40 years,
    just tell them the finish size of the hole and thats what you are paying for.

  8. #18
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    The steel liner needs to be ground away where he didn't go far enough towards the end--it's not aluminum, unfortunately. I can cut away material off the piston for clearance.

    I can visually see the new hole is offset. Grrr!

    Thanks for the comments.

    Jeff

    PS: I intend to spin the crank with one rod/piston (no rings) and see if it doesn't hit. I'll blue it with marking paint to make sure. Cripes!
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  9. #19
    Team Member zul8tr's Avatar
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    Your machinist knows nothing about blind bores I believe he used yours as a Beta test. What a jerk. Is he local or did you have to mail your block? If local why not bring it back and have him fix it if you trust that he will not make it worse?? What a mess to deal with. IMO hand grinding the sleeve will not be easy and certainly not precise. Good that the rings do not ride there.
    " Three may keep a secret if two of them are dead" Ben Franklin

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  10. #20
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    ..."IMO hand grinding the sleeve will not be easy "

    That's why I didn't consider trying it. I DID relieve the piston with a pencil grinder and a file, and it WORKS! Had to take a bit more off in a few places, but she spins over nicely with my drill and doesn't hit. In fact, I got all the pistons and crank back in and am ready to complete the build.

    Thanks so much for all your advise!

    Jeff

    PS: At my age (76) this might be my last build, so I'm trying hard to make it a good one.
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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