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  1. #1

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    Reuse stock connecting rods from failed engine??

    I picked up a really nice 2006 4 tec block from a GTI 130 with very few hours on it. Its so clean looking that you can eat off it.. Machinist will determine to bore, if so, how much oversized..
    From my failed engine which I rebuild, it was fitted with Molar connecting rods and .5mm Oversized CP pistons.

    When the failed engine was disassembled, #2 piston was found to be the problem, it melted at the top edges. #2 connecting rod showed blue/black discoloration at the large end. Discoloration was on the large end, thin, flat, circular side surface near the beginning of the rod's H formation on both sides. The large end bearing showed extreme heat but didn't damage the crankshaft journal and all main bearing where good.


    #1 and #3 connecting rods showed no discoloration or signs of heat, same with their large end bearings, look like new.

    My question is.. Would it be okay to reuse #1 and #3 Connecting rods for the second engine build?
    It won't be for a turbo application but perhaps up to 15 psi @ 8600 may be in the works for it.


  2. #2
    Quote Originally Posted by tiderider View Post
    I picked up a really nice 2006 4 tec block from a GTI 130 with very few hours on it. Its so clean looking that you can eat off it.. Machinist will determine to bore, if so, how much oversized..
    From my failed engine which I rebuild, it was fitted with Molar connecting rods and .5mm Oversized CP pistons.

    When the failed engine was disassembled, #2 piston was found to be the problem, it melted at the top edges. #2 connecting rod showed blue/black discoloration at the large end. Discoloration was on the large end, thin, flat, circular side surface near the beginning of the rod's H formation on both sides. The large end bearing showed extreme heat but didn't damage the crankshaft journal and all main bearing where good.


    #1 and #3 connecting rods showed no discoloration or signs of heat, same with their large end bearings, look like new.

    My question is.. Would it be okay to reuse #1 and #3 Connecting rods for the second engine build?
    It won't be for a turbo application but perhaps up to 15 psi @ 8600 may be in the works for it.
    Others may have a different opinion, but on past engines I have built using parts from catastrophically failed engines, my view is that connecting rods can be reused from cylinders that have no drama. For example, on an engine that drops a valve in #1, I would reuse connecting rods from the other two cylinders as long as there is no visible damage to those pistons. I would not reuse a connecting rod from a cylinder with any damage at all on the piston. The one exception is from engines that failed from hydrolocking. I won't reuse any rods from the cylinders that look good, because when one cylinder fails from hydrolocking, damage can exist in the other cylinders that isn't visible. The rods may look OK but will find their way out into sunshine when reused.

  3. #3

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    Quote Originally Posted by Sea Dood View Post
    Others may have a different opinion, but on past engines I have built using parts from catastrophically failed engines, my view is that connecting rods can be reused from cylinders that have no drama. For example, on an engine that drops a valve in #1, I would reuse connecting rods from the other two cylinders as long as there is no visible damage to those pistons. I would not reuse a connecting rod from a cylinder with any damage at all on the piston. The one exception is from engines that failed from hydrolocking. I won't reuse any rods from the cylinders that look good, because when one cylinder fails from hydrolocking, damage can exist in the other cylinders that isn't visible. The rods may look OK but will find their way out into sunshine when reused.
    Thank you for this GREAT advice!
    I just purchased a New set of Molnar Connecting rods for $300.. Early Black Friday!!
    I installed a set in the first rebuild and honestly, they are VERY NICE.

  4. #4
    moparguy's Avatar
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    Quote Originally Posted by tiderider View Post
    Thank you for this GREAT advice!
    I just purchased a New set of Molnar Connecting rods for $300.. Early Black Friday!!
    I installed a set in the first rebuild and honestly, they are VERY NICE.
    Where did you get em?

  5. #5

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    Quote Originally Posted by moparguy View Post
    Where did you get em?
    It was an online seller who had 1 last set in stock.. Good timing!! $60 is connecting rod bolts alone if I would have replaced only 1 OEM con rod.. Molnar con rods come with ARP2000 reusable bolts. Honestly the stretch bolt method isn't that time consuming or difficult at all..

  6. #6
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by tiderider View Post
    Thank you for this GREAT advice!
    I just purchased a New set of Molnar Connecting rods for $300.. Early Black Friday!!
    I installed a set in the first rebuild and honestly, they are VERY NICE.

    a very wise move going with new con rods. good luck on your build

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