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Should the gudgeon pin clips be replaced at rebuild?

Engine Issues

  1. 70Hardtop

    70Hardtop Well-Known Member

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    What is the consensus from experienced engine builders on replacing the retainers of the piston gudgeon pins (wrist pins I think you call them ?). I am doing a budget rebuild on a 1967 273 with full floating rods. It will be a mild performance rebuild with mild solid cam, Weiand intake, headers etc, expecting about 290-300 HP. I am reusing the original pistons because the engine was in such amazing original condition when I disassembled it, pistons hardly worn and I got a hone on the bores and using some nice worked over conrods which have been sitting around for many years, been weight matched and shot peened and resized + ARP bolts. (using new rings/bearings of course) The wrist pin retainers have been there nearly 50 years, they are just wire spring clips. They don't do much work but can they be a point of failure after a lot of miles?

    I can just buy some new circlips but is it a good idea?, or necessary on a mild street driven engine?

    thanks
     
    Last edited: Feb 10, 2018
  2. budascuda

    budascuda Well-Known Member

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    I read somewhere that spring steel has a fatigue time, depending on the specifics.
    One of the things that shortens the life of a spring is repeated heating and cooling, specially at extremes.
    Also, physically unloading and re loading a previously heat fatigued spring could cause it to develop cracks or cause numerous other problems. These problems may not be visible at first but that changes with time, specialty if the spring goes through repeated heating/cooling afterwards, again!
    So I think if one has to reuse a spring. It's best not to de compress and then re compress it again.
    Just leave it in compressed mode and re use it.
    IF YOU HAVE TO!
     
  3. 70Hardtop

    70Hardtop Well-Known Member

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    Thanks for good reply Budascuda. Better than a lot of other answers I got on another forum. It has confirmed my thoughts about spring steel and heat cycles and even though these clips are not a stressed component, still..... I have gone and bought circlips anyway. But as someone else pointed out, the groove in the piston is machined for that type of round wire clip so I will inspect closely how the circlips fit compared to the original wire clips.
     
  4. budascuda

    budascuda Well-Known Member

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    You are quite welcome, I hope the circlips do the job right.
    Good luck mate!
     
  5. aussiemark

    aussiemark Well-Known Member

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    Like all clips regardless of wether they are used to hold piston pins or transmission gears, once removed you should fit new ones. When I used to freshen the engine in my motorcycle I would remove one clip, slide the pin out that side and when I put it together I would just replace the one clip I removed with a new one this saved wear and tear on the clip grooves in the piston and I never had a failure. If you don't remove them they will be fine and not fail they get damaged during removal and are never perfectly round so they will fail if reused, it is cheap insurance to replace them every time they are removed. Also the clips that have two small holes for circlip pliers have a flat side with a sharp edge and a rounded side with a smooth edge the sharp edge should face out to resist being pounded out of the groove.
     
    Last edited: Feb 14, 2018
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  6. budascuda

    budascuda Well-Known Member

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    That's the ticket!