Wrist Pin Material (Automotive)
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  1. #1
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    Default Wrist Pin Material (Automotive)

    What would be a good Bronze material to use for wrist pin bushings in a big block Chevy? I want to make my own custom bushings just to say I did. any help would be appreciated.

    Thank You
    Last edited by Atvnut; 01-27-2013 at 03:37 AM.

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    Too much risk, too little reward.

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    Quote Originally Posted by S_W_Bausch View Post
    Too much risk, too little reward.
    What, to answer the question, or to make the bushing?

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    Read your Q several times and I'm still a little confused

    Do you want to make the actual wrist pin out of bronze, or just the bushing that goes in the connecting rod.

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    Quote Originally Posted by Limy Sami View Post
    Read your Q several times and I'm still a little confused

    Do you want to make the actual wrist pin out of bronze, or just the bushing that goes in the connecting rod.
    sorry about that. I am looking to make the bushings thank you

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    You are crazy. Buy them. Do you have a way to O/S the rods to make room for the bushes? How about a Sunnen hone to size them after you press them in? If you don't even know what to make then out of I don't see much chance of this venture ending having a happy ending.

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    Race, street or what? The application matters. An often used alloy for performance parts is aluminum silicon bronze, C642. If the engine is really serious there are step ups from there.

    Hope you know how important the OD of the bushing is, faults in geometry or surface finish doom the bushing.

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    Quote Originally Posted by moonlight machine View Post
    You are crazy. Buy them. Do you have a way to O/S the rods to make room for the bushes? How about a Sunnen hone to size them after you press them in? If you don't even know what to make then out of I don't see much chance of this venture ending having a happy ending.
    some particular rods come with bushings bigger then i desire i am willing to make mistakes. I have googled the materials and would just like a second opinion. I am sure no one has ever built something on here that would of been simpler to buy.

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    Quote Originally Posted by DaveE907 View Post
    Race, street or what? The application matters. An often used alloy for performance parts is aluminum silicon bronze, C642. If the engine is really serious there are step ups from there.

    Hope you know how important the OD of the bushing is, faults in geometry or surface finish doom the bushing.
    I would hope it to be a big step up in time.

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    I make quite a few wrist pin bushings for oddball rods and obsolete / ''special'' engines, and use Nickle Aluminium Bronze, not had one come back - YET!

    All mine are pressed in and honed to final size by my customer.

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    The correct answer is to use smaller diameter DLC coated wrist pins, which are not only lighter but stronger and do not require a rod bushing. That also allows the con rod to be smaller and lighter. SAB is expensive, but NAB costs are very high.

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    I realize that some of us (me?) come off a bit harsh, but then, the environment of an internal combustion engine is a bit harsh.

    It's a good thing that engine components can't talk, I suspect most of the components would have a grievance.

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    Use Ampco 18

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    Quote Originally Posted by Glenn Wegman View Post
    Use Ampco 18
    What he said.

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    If you are using stock rods I would not weaken them by installing bushings.Depends on what RPM & power you are trying to make.The original L88 rods were honed for clearance and copper plated.Never seen one fail at 550 plus Hp 8k rpm.Also have converted many press pin stock rods to full floating by honeing for clearance and adding oil hole in rod.That was 40 years ago,maybe the laws of physics have changed since then?
    Randy

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    Make them all the time.(never for a chevy however).Use Ampco 18 or C642 bronze.....lots of rods in service, no failures.
    Same material that Carrillo uses in the little end of their after market rods.

    You can get away with about .016+" wall and still hold the press. I bore the bushings to the pin size on the lathe and size for clearance on the hone after pressing
    them into the little end. You will need about .001-.0013" clearance when finished up...tighter than that and the material growth will make the up tight on the pins
    at operating temp.....Factory style steel backed bushings don't need as much clearance...Will give a quieter engine when cold.

    Cheers Ross

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    Having worked in a powertrain engineering development shop for around 3 years and an engine plant for 2 years and having to maintain a machine pushing conrod pins thru rods and pistons every 4 seconds, the fit is very very close and it must be in that application. Half a thousandth or better diametral clearance is a must to prevent the rattle you will hear from the driver's seat. I would make up 30 rods and find an instrument sensitive enough to measure them all and assign them into buckets of .0002" then pick the best ones and go from there.

    The cost of being "wrong" on this particular assignment is pretty high. Even if you decide to pull rods in the vehicle...you drop the pan..you remove the heads, you undress all the wiring, fueling, cooling. Huge mess. Scrape off the gaskets getting no junk in all the oily surfaces. Oil drips on you as you replace all the rods, buy a new gasket kit and start over...seems like a week in prison would be better just kidding of course but you get the idea. I build engines using RTV for the covers which requires super clean and dry surfaces, and its something I only want to do Once.

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    Quote Originally Posted by matt_isserstedt View Post
    Having worked in a powertrain engineering development shop for around 3 years and an engine plant for 2 years and having to maintain a machine pushing conrod pins thru rods and pistons every 4 seconds, the fit is very very close and it must be in that application. Half a thousandth or better diametral clearance is a must to prevent the rattle you will hear from the driver's seat. I would make up 30 rods and find an instrument sensitive enough to measure them all and assign them into buckets of .0002" then pick the best ones and go from there.

    The cost of being "wrong" on this particular assignment is pretty high. Even if you decide to pull rods in the vehicle...you drop the pan..you remove the heads, you undress all the wiring, fueling, cooling. Huge mess. Scrape off the gaskets getting no junk in all the oily surfaces. Oil drips on you as you replace all the rods, buy a new gasket kit and start over...seems like a week in prison would be better just kidding of course but you get the idea. I build engines using RTV for the covers which requires super clean and dry surfaces, and its something I only want to do Once.
    I have a pet peave, I work with mostly Ford engines. I use big block chevy rods there is quite a difference in the pin diameter, BBC .990 Ford can be either .912 or aftermarket Small block Chevy .927. To mock up a motor it has to be bored etc to determine deck height. If I off set my wrist pin bushings I can effectively save on taking the engine back to the machine shop, to aquire the proper deck clearance.

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    Thank you all for your help

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    For anyone who may read this and want to do it on a newer engine, be aware that many of the engines in the last 10-15 years or so have profile bored / honed bushings or shapes in the small end (even if no bushing). This is to account for the bending of the pin during operation. Failure to maintain this very engine specific profiled shape in the pin end will result in excessive point loading at the edges of the small bore of the rod. The end result of not having the profile will either be cracked small ends of the rod or pin breakage / deformation.

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