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Thread: LSA piston questions

  1. #1
    ronr's Avatar
    ronr is offline Cadillac Owners Enthusiast
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    LSA piston questions

    I bought a used LSA short block to replace the cracked LS6 in my car. It's in the machine shop for freshening and I just got a call that 2 of the cylinder bores are .005" out of round at the top (thrust surfaces lower in the block look okay). The machine shop is suggesting bore 1 size over (.010"??) and replace pistons/rings.

    I'm thinking this makes sense since I've already got it torn apart and in the shop and it gives me a good excuse to look at upgrading to forged pistons. I do, however, have more questions than answers now:

    Would .010" oversize be the correct "one size over" bore and what would that make the bore diameter (I've only been able to find a GM Marine LSA brochure which lists the bore as 103.25mm)?

    Does GM have a "stock" oversize piston I could buy instead of upgrading to fully forged? If so what is the part number?

    Do the aftermarket piston manufacturers make pistons (pins) compatible with the stock LSA rods or will I have to upgrade those in the process also? If so, who and which?

    Should I skip boring all together since it's just at the top of 2 cylinders, "hone 'em and let the rings do their job"?


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  3. #2
    DMM's Avatar
    DMM is offline Cadillac Owners Fanatic
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    Re: LSA piston questions

    I'd have them re-measure and provide the numbers. They would not need to bore it, a finish hone would be more in line with what is actually done on LS motors. Consider LS1/6's are finish honed to accommodate 3.905" pistons from the original 3.898" bore. I believe .010" is the absolute max for the OE cylinder liners as well.

    I advise them to re-measure as finish honing is a standard practice with LS motors, and if they're actually trying to charge for a bore/hone they're certainly taking you for a pretty expensive ride. I would measure for myself and most likely leave things as is, honestly.

    It's almost Xmas time...everyone needs money.

  4. #3
    SC2150's Avatar
    SC2150 is offline Cadillac Owners Connoisseur
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    Re: LSA piston questions

    Agree w/DMM. Good advice.

  5. #4
    PISNUOFF Guest

    Re: LSA piston questions

    Wash....240 ball hone....420 plateau brush.....aftermarket rings....wash....done.


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