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Subject: Rod bushings

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BW    Posted 12-10-2020 at 20:22:10 [URL] [DELETE]        [Reply] [Email]  
  • Rod bushings
  • I suspect I know the answer to this question (machine shop) but thought I would ask anyway.
    Is there any way to reliably hone rod bushings that is within the capabilities of an amature at home shop? The closest machine shop is 3 hours away. Made a couple trips to get my crank ground but now that I have the engine rebuild parts I need to have the rod bushings installed/sized. Pretty sure I can handle the removal and installation but suspect they need to get sized at a machine shop.
    Old bushings appear good as the pins will push thru with slight pressure but the rest of the engine will be totally redone so probably should do it right.
    Thanks

    TheOldHokie    Posted 12-11-2020 at 08:57:54 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Rod bushings
  • Depends on how well equipped your shop is. Honing the small end bushing to size is a relatively new process. The traditional process was reaming to size which is quite easy. The harder part is keeping the centerline of the small end square in all three planes with the centerline of the big end. This is of greater importance on a higher RPM and HP engines and of somewhat less importance on a low RPM and HP tractor engine. The traditional engine builder's shop used a jig to hold the reamer square. You could achieve acceptable results at home with a small milling machine/quality drill press/hand reamer and some creative fixturing.

    TOH


    Reaming the Gudgeon Pin



    BW    Posted 12-11-2020 at 15:26:11 [URL] [DELETE]        [Reply] [Email]  
  • Re: Rod bushings
  • Thanks TOH.
    Not sure if I will attempt it yet or take them to a shop. No milling machine, just a drill press ect. I may attempt to make some sort of jig to hold everything straight, if it looks like it would work I may give it a try. Worst scenario is I screw it up and need to order more bushings and then have a shop do it.
    Does anybody ever reuse the old bushings on a rebuild? Hadnt planned on reusing them but I have been referencing the "overhauling an engine" in the "how to" on this site and it seemed to suggest reusing them would be fine if within tolerances?

    mhb@ufe    Posted 12-12-2020 at 14:21:56 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Rod bushings
  • I have reused the old ones many times if they are within tolerance. If you don't have the proper equipment or have a machine shop fit them the old ones could fit better than poorly done new ones. The slow turning low compression N engines are not hard on the wrist pin bushings.

    Mark

    BW    Posted 12-12-2020 at 14:58:55 [URL] [DELETE]        [Reply] [Email]  
  • Re: Rod bushings
  • Was thinking along the same lines, would be better to reuse the old ones then to do a half a** job at replacing them. TOH provided some good info but I am not set up or confident enough to do it myself.
    Will be taking them to a shop and have it done. Every bolt on this project has been removed and everything replaced or repaired properly so far, hate to cheap out now.

    mhb@ufe    Posted 12-12-2020 at 18:31:35 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Rod bushings
  • It sounds to me that if you don't replace them it will stick in your mind and you will always wounder if you should have. Peace of mind does have value.

    Mark

    TheOldHokie    Posted 12-11-2020 at 16:28:49 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Rod bushings
  • Assuming you have new pistons and pins new bushings would be in order.

    A lot depends on how much undersize the new bushings are right out of the box and how much material you have to take out. If its just a few thousandths then a $20 ball hone in your drill press will get the job done (see video link), If it much more than that I would use the drill press and a fixture to first ream to rough size (.001/.002 )undersize and finish with the ball hone.

    The idea is the hone isn't being used to take out much material. Alignment is not going to be critical if you have them square and sized close to start off. This video shows a professional engine shop honing rods on a "high dollar" Sunnen rod hone. At about 50 seconds in you can see them doing the small end bushing. Hardly a precision alignment - all they are doing is fine tuning the final fit ;-)

    Honng Connecting rods

    TOH

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