Con Rod Cracks

Discussion in 'PSI Superchargers Tech Questions' started by oldskooldigger, Jan 10, 2009.

  1. oldskooldigger

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    Anybody ever seen a rod try to split through the thickness? I have (6) C&A 250 rods that, in varying degrees, have cracks originating in the large end bore and propagating through the screw hole to the outside.

    Maybe a better description is to say the width of the big end of the rod is 1.00", and it's trying to split into two .50" sections right through the center. There's machining marks/stress risers on the outside, but the crack starts on the inside.

    Rods had (30) runs on them and I was getting ready to cycle them out, (thankfully I caught it). Caps do not have cracks; bearings look good; plugs look good. Here's a bit of info for the condition of threads.......the rod that is cracked completely through the bolt hole still will hold torque (95 lbs, A-1 bolt).

    Also, I just rec'd a set of MGP rods for replacements and they look super. Thanks to those who recommended them on other threads.

    Thanks,
    Steve K.
     
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  2. marklee

    marklee Blown Alcohol Dirt Drags

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    split through rod hole.

    sounds like detenation to me. what side of rod or is it both sides??
     
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    Last edited: Jan 10, 2009
  3. jim phillips

    jim phillips ta/fc

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    i agree detenation causes some strange things to happen cracks,sunk pistons, twisted rods, holes in pistons, loose blower studs bolts is a dead give away after one pass ect..............
     
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  4. secondwindracing

    secondwindracing top alcohol

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    are your c&a rods and your mgp rods gram out the same??? if not you better get it reballanced..Dave
     
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  5. oldskooldigger

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    #6 cracked through on both sides and halfway up bore on one side. Crack appears to originate on side of rod toward camshaft. I've not seen signs of detonation on the plugs or bearings. Is it possible for detonation to damage the rods before before the plugs or bearing?

    Dave, I'm fitting the pins today and plan to weigh them as well. Thanks. I'm thinking they will be lighter. I've always run neutral balance, but if these are indeed lighter I was considering keeping the overbalance and running with them. How much overbalance is acceptable?

    Thanks,
    Steve K.
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    Call Brian Scollon at GRP 303.935.7565 and discuss it with him. He is a good man to talk to.
     
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