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Thread: Tight wrist pins with new small end bearings????

  1. #1
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Tight wrist pins with new small end bearings????

    I am currently rebuilding the 20v engine in one of my Levins.
    I replaced the small end bearings in the conrods, but after doing so, the existing wrist pins are really tight.

    Is there something I'm not doing right? I made a tool to press the old bearings out and the new ones in and it worked fine. The was no dramas there.
    But when I went to put the pistons back on, the wrist pin is uber tight in the new bearing. I though it would have been a bit on the loose side with the pins having been slightly worn?

    I don't want to have to buy new pistons etc, so how do I make this work?

  2. #2
    Junior Member Too Much Toyota
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    Default Re: Tight wrist pins with new small end bearings????

    heat the pistons up (bath of boiling water will do the trick), lube up the pin and it should slide in with some gentle tapping from rubber mallet.

    edit: i made up a holder to sit the piston sideways to i could tap the pins in vertically - consisted of two cork sanding blocks affixed to a lump of wood.
    ------------------------------
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  3. #3
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    The pin slides through the piston ok, but it isn't sliding through the bearing as it should (where the motion should be, ie. there's zero oil clearance).

    I just read in the Blacktop engine manual that I need to use a 'pin hole grinder' to enlarge the bearing to the correct size.... I might take them all to the engine shop around the corner from work, I don't have a pin hole grinder on hand.


    I might use your holder idea. I used to use cardboard taped to an old brake drum. Gotta move quick with hot metal when the gudgeon pin is an interference fit (Damn 4E/5E engines).

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    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    did you hone the new bushes in?

    you can do it by hand with some fine wet/dry, until the pin feels about right. obviously keep each slug/rod/pin as a matched unit after honing.
    There is no substitute for PUBIC inches

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  5. #5
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    Yea, I figured out I need to do something like that. Maybe a small fine-grit flap wheel on the drill press at low speed?

  6. #6
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    no just do it by hand you will have to take 3/5 of fuck all material off. go too far and they get sloppy, may as well have left the old ones
    There is no substitute for PUBIC inches

    Never late in an x8

  7. #7
    i wrote the Automotive Encyclopaedia roadsailing's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    ideally you should have got the little ends and pistons sized by your engine rebuilder, 4AGEs have fully floating gudgeons, so the pin should rotate fairly freely in the piston and con rod (4ACs are pretty much a press fit in the con rod from memory)

    are the big ends sized right? are the rods straight?
    like to drift? live in victoria?
    www.vicdrift.com

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    formerly shinybluesteel

  8. #8
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    Yea, all the rest is good and sized ready to bolt back together after the usual clean and double checking of clearances, I just decided to replace the small end bearings while I was at it.

    The Toyota manual says you just need to size the small end to achieve the correct clearance with the gudgeon pin, specified at 0.004 - 0.008mm.

  9. #9
    Junior Member Automotive Encyclopaedia 2jzhilux's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    Your local engine builder will resize these correctly for not much money, why take the gamble on doing it wrong?

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    Junior Member Automotive Encyclopaedia
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    Default Re: Tight wrist pins with new small end bearings????

    They need a tight sliding fit, thick lube or just heating up the pin in your hand will make a noticeable difference.
    Machine shops have enough trouble not honing them bell mouthed, DIY it is almost guaranteed.
    Oil hole/s lined up and cleaned up & deburred with a bevel/radius/chamfer?
    'I've scrapped better.' John stated when asked about the car by the guy with the silver tipped cowboy boots!

  11. #11
    Junior Member Grease Monkey
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    Default Re: Tight wrist pins with new small end bearings????

    That all depends who your local machine shop is.............
    It isn't that hard with a bit of fine wet & dry either, Just be sure to move the wet & dry up and down as well ae around when you do it, similar to honeing a bore.
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  12. #12
    Junior Member Too Much Toyota
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    Default Re: Tight wrist pins with new small end bearings????

    Sorry TERRA, thought it was the piston that was tight.

    Diy approach is to use a brake cylinder hone but a workshop would be far safer.
    ------------------------------
    ST185 road barge / MZ11 forest barge / RA65 garage barge

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    now with 7m powaz Automotive Encyclopaedia hosking1991's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    The tolerance is about 0005" to around ".0009 , that's less than a thou ! No way in hell I would do it by hand (ovality and taper would be pretty far off doing it by hand )

    Engine reco shop wouldn't charge much seeing as though you have fitted them already

    Btw you probley have already but make sure the oil hole in the bush lines up nicely



    Cheers luke

  14. #14
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Re: Tight wrist pins with new small end bearings????

    Yeah, the oil holes are all sweet and it's all good to go except the tightness. I might take them around the corner to the engine shop on Monday.

  15. #15
    Junior Member Backyard Mechanic
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    Default Re: Tight wrist pins with new small end bearings????

    for what it costs, get an engine builder to do it.

    on a side note (sorry to hijak), where did you buy the little end bushes? OEM Toyota?
    SHEPPO..

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