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Whats the general consensus on bushing wrist pins?

Discussion in 'The Hokey Ass Message Board' started by tlmartin84, Nov 13, 2012.

  1. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
    Member
    from WV

    Seems like this is perhaps my only option to make something "off the shelf" work.

    Is this an acceptable way to do things, is there any adverse affects on engine wear?

    My connecting rods have a diameter of .975, most of the pistons available with the correct diameter and compression height are .927.

    How is this done? bushing pressed into the connecting rod? What are they typically made of? Can you buy them somewhere or does it have to be done at a machine shop?
     
  2. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,053

    ROADSTER1927
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    Bushing the rod top is fine and yes they need to be fitted after instalation. Have a great day Gary
     
  3. oldolds
    Joined: Oct 18, 2010
    Posts: 2,114

    oldolds
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    Is there enough material in the pistons to enlarge the pin hole in them?
     
  4. Mike VV
    Joined: Sep 28, 2010
    Posts: 827

    Mike VV
    Member

    Any "competent" shop should be able to do this for you. Basically...done all the time to "full float" wrist pins that came from the factory as "pressed in".

    Many are bronze, pressed in and final honed (fitted !) to fit the wrist pin. The engine application and materials will dictate the oil clearance (normally in the .0007/.0009 range for a street engine).

    Mike
     
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  5. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
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    from WV

    Nope, the wrist pin is already in the oil ring on a lot of these pistons.
     
  6. onetrickpony
    Joined: Sep 21, 2010
    Posts: 280

    onetrickpony
    Member
    from Texas

    Full floating pins also require some way to hold the pin in the piston. Either a nylon button between the end of the pin and the cylinder wall (drag race stuff, probably not recommended for street use) or the piston needs snap ring grooves in the wrist pin holes to keep the pin from walking out. This usually means a more expensive piston.
     
  7. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 4,388

    56sedandelivery
    Member

    Of course, Chevrolet did this with the original Z-28, 302 engines; only they did not bush the rod end. It was direct, slip contact between the rod end and the pin (you already have too much clearance for that to be done). As already mentioned, there has to be a way to retain the pin in the piston. You can get Speed Pro and KB pistons, both hypereutectic and forged, that work with pressed or full floated pins, fairly cheap. For the amount it will cost to rebuild your current rods, you could buy a set of after market Eagle/Scat/XYZ brand replacement rods, or even rebuilt factory rods, from that auction site we all know and love. Butch/56sedandelivery.
     
  8. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,173

    Dan Timberlake
    Member

    The back of the Sealed Power Engine catalog (and others) used to have parts listed in order of size. " Progressive size " listings. it was easy to look for pin bushings (or any other parts) that could be used for projects. I'd expect a replacement bushing already exists that can be used with minimal rework to be a press fit in the rod eye.
    0.927" sounds like SBC wrist pin.


    The best way to finish the pin bore is align boring it parallel to the finished big end bore to create a 'straight" rod. Assumptions about accuracy of the rod side faces or the original pin bore are dangerous.

    It is desirable to have 0.020" or more material in bushing bore.
    With enough material it is possible to equalize the lengths of the rods too. Just finish honing the installed bushing follows the original bushing bore with no control of rod length or straightness.

    Tobin Arp is one company that made machines for align boring rod bushings. Ours had nicely made expanding mandrels that gripped the big end bore directly.
    http://www.rhynecompetitionengines.com/assets/images/db_images/db_shop_0221.jpg

    Probably should add some oil holes to the rod eyes. There used to be plenty of theories of right and wrong ways to do that. Original 426 hemi had no holes as I recall.
     
  9. Just another opinion;

    Unless you plan on taking the pistons off of the rods often, there is no advantage in having full floating pistons. With each additional clearance point, you give the piston more chance to rock sideways in the bore.

    You could just have your rods honed to the correct size to fit the .927 pins and have the pins installed as a press fit.
     
  10. porknbeaner
    Joined: Sep 12, 2003
    Posts: 38,751

    porknbeaner
    Member

    Yea for sure honeing it smaller is a damned good trick. :rolleyes:

    Bushing the rods is fine when done by a competant machinist, take them to the machine shop and have them bushed and fit. Done deal.
     
    falcongeorge likes this.
  11. Heo2
    Joined: Aug 9, 2011
    Posts: 661

    Heo2
    Member

    I realy like to se that machine that can hone down the hole
    from 975 to 927 must be some new fantastic invention
     
    falcongeorge likes this.
  12. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
    Member
    from WV

    Would solve my dilemma if there was!
     
  13. SimonSez
    Joined: Jul 1, 2001
    Posts: 1,621

    SimonSez
    Member

    Wow, you've got a magic hone that can make holes smaller? :)

    The OP has rods has a small end diameter of .975 and he wants to bush them to use pistons with a .927 pin diameter.


     
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  14. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
    Member
    from WV

    I have found a rod that has a .912 diameter end, whats your thoughts on honing/boring them out to .927? 15 thousandths.
     
  15. porknbeaner
    Joined: Sep 12, 2003
    Posts: 38,751

    porknbeaner
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    maybe you could get them metal sprayed then honed to fit. ;)
     
  16. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,053

    ROADSTER1927
    Member

    That will work just fine for pressed fit or full float. Gary:)
     
  17. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
    Member
    from WV

    what do you think of the last scenario P and B??
     
  18. porknbeaner
    Joined: Sep 12, 2003
    Posts: 38,751

    porknbeaner
    Member

    It would depend on how much meat you have to work with. If I looked at it and it was not going to be any different than a bushed rod and I had them to use I would just hone the rods and run with it.

    The thing is that what you are talking about is a floating wristpin, correct? the pistons have keepers? If that is the case it is not a press fit and you will need to give yourself some clearance for the wrist pin so it will be more like .017 and not .015.
     
  19. This is the HAMB, and you know we like photos. But in the absence of that, at least fill us in on some details! What engine combo are you trying to build? Just really curious!!!
     
  20. Hey, I wear glasses fer a good reason, also my reading compression isn't up to snuff on all occasions either.

    That was one of my dumber reading errors. :eek:

    By the way, I used to run a Tobin Arp rod boring table back in the 70's so I know how hard it is to shrink a hole.
     
    Last edited: Nov 15, 2012
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  21. tlmartin84
    Joined: Jul 28, 2011
    Posts: 760

    tlmartin84
    Member
    from WV

    LOL, I don't have any pictures.......I am trying to piece this thing together before taking the plunge and spending the money.

    I am building a Ford 300 inline 6. Rather than use the stock 300 rods, the plan is to use longer 240 rods and a shorter piston, a small block ford stroker piston (331 or 347). That will give me a nearly identical compression distance and improve the rod ratio, reduce wear, and maybe gain a little more torque while I am at it.

    The 240 rods had 2 options, .975 and .912 wrist pins depending on years. I can find .912 stroker pistons that are forged......I just don't think the extra money getting them is worth it. Hyper's are cheaper and should hold up fine for what I am wanting but most come with the more common .927 pin.
     
  22. Without having the rod in my hand to measure the ends, that would be foolish to speculate. However, yes possible to hone them to pin fit for a pressed pin.

    You will generally run into a issue with integrity and strength if you try and make them floating and open up the small end for the O.D. of the appropriate sized bushing.

    In the old days, some engine builders would run a non bushed full floating rod end, but this after careful placement of oiling holes and only generally for short track use.
     
  23. If you are concerned with strength of the .912" pin, you can have custom thick walled pins made. TR
     
  24. wmc
    Joined: Feb 5, 2014
    Posts: 13

    wmc
    Member

    Ok, nobody flame on me for digging up a four year old post but... I am doing the EXACT same thing and attempting to locate a wrist pin bushing to fit the .975 rod so I can use small block FORD size pistons/pins @ .912 and every major hot rod company caters nearly ONLY to chevy parts... not dissing chevy, I just do not want anything chevy in my Ford! TLMARTIN84 - did you ever solve the issue? What did you come up with? or anyone else that has done this please chime in, unless you're dead set about convincing me to do something else then please no comment. Thanks for any help!
     
    Last edited: Oct 20, 2016
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  25. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 1,312

    Kerrynzl
    Member

    Hahaha! Don't be silly.
    All he needs is to stick the .975" pins in a lathe and machine down both ends to .927 :D
     
    falcongeorge likes this.
  26. doyoulikesleds
    Joined: Jul 12, 2014
    Posts: 128

    doyoulikesleds

    another option for a 300 six is to use 390 pistons if your trying to build cheep power
     
  27. sunbeam
    Joined: Oct 22, 2010
    Posts: 2,887

    sunbeam
    Member

    Ford 240 and 300 rods in the 60s used .912 sbf pin size later went to .975 early rods will easly go to .927 sbc chevy size. plus by offsetting the pin you can change the length a little. A 350 6" rod piston would be close. Or if you want to use a bushing a Y block bushing could be made to work.
     
    Last edited: Oct 22, 2016
  28. wmc
    Joined: Feb 5, 2014
    Posts: 13

    wmc
    Member

    Using the 240 rod on the 300 crank there is only 1.2153 CH left, I was looking at using the ford stroker pistons but I wanted floating pins... hence the reason for the bushing and the .975 rod so reaming isn't hopefully not needed as much to run the .912 pin (leaves more meat on small end of rod). Whole idea is to reduce piston weight/size and longer rod less angle (stronger) especially when running higher compression and high duration bumpstick. I just need to find a company that lists all their floating pin bushings by size, find the right one or close and buy. If this was a smallblock V8 that would be easy... but it is not. I have a set of the early rods, but I want floating pins and the early rods are a lot thinner at the top than the late 240 rod, plus the added bonus of having the oil squirter for the cylinder walls (controversial, some say no hole more oil to crank). Anyhoo, I guess I am left with just keep digging. Thanks.
     
  29. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,053

    ROADSTER1927
    Member

    I bushed my olds rods for Chevy wrist pins that were smaller. I full floated them and used bushings that were for a Wisconsin engine, found by size. They fit the rod and needed honing on the inside. Gary
     
  30. wmc
    Joined: Feb 5, 2014
    Posts: 13

    wmc
    Member

    Thanks roadster1927! Never thought about looking into the stationary engines! I Finally found some last night! 272/292 ford V-8 bushings, their a tad on the long side but id/od is correct! Hopefully they'll work out.
     

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