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| removing pressed gudgeon pins https://www.ausmini.com/forums/viewtopic.php?f=2&t=31150 |
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| Author: | volkmini [ Thu Apr 26, 2007 8:24 pm ] |
| Post subject: | removing pressed gudgeon pins |
hi, i'm having a bit of trouble trying to work out how i'm going to remove the pressed gudgeon pin from my piston/conrods. i have been told that you have to have a special jig for removing them. is this true. and are there anyother ways of removing the pins |
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| Author: | drmini in aust [ Thu Apr 26, 2007 8:49 pm ] |
| Post subject: | |
That is true, you either need a special service tool (as illustrated in original BMC workshop manuals) or a hydraulic press, and some tooling to suit. Any engine reconditioning shop can do it for a minimal sum, they have the gear. Likewise for fitting new ones- best let them do it, new pistons cost good money. 
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| Author: | Mike_Byron [ Thu Apr 26, 2007 10:27 pm ] |
| Post subject: | |
I dont want to hog in on the good doc's advice but I become nervous when somebody asks a question indirectly or directly about replacing pistons. Everything Doc said is good advice, however, mini engines nearly always wear the bore into a taper and oval in shape. Unless you have very carefully and accurately measured up all four bores with any wear and found them to be usable then simply fitting new or exchange pistons and rings is a disater waiting to happen. Since you have to go to a bare block anyway - whizz it off to a machine shop to have it properly chemical cleaned, measured and assessed. Old motto - "do it properly - do it once" |
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| Author: | willy [ Thu Apr 26, 2007 10:35 pm ] |
| Post subject: | |
Bang them out with a really large hammer
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| Author: | drmini in aust [ Fri Apr 27, 2007 6:46 am ] |
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willy wrote: Bang them out with a really large hammer
It would want to be a 3 ton one... 
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| Author: | glenno [ Fri Apr 27, 2007 7:04 am ] |
| Post subject: | |
The rods are actually induction heated to expand the bore-the pin slid in/out and then left to cool......effortless...spent the cash on new pistons? -then spend a few more bucks and have the professionals do it......most engine recon shops should have the tool..... The fit of the pin in the rod is a heavy interference fit.......... |
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| Author: | TheMiniMan [ Fri Apr 27, 2007 9:28 am ] |
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it`s quite funny really,,, sooo many people know how it`s "Normally" done,,, & re-read what i typed there--> "Normally" & i`m not bagging anyone here, no offence to anyone at all , truly!!!!! That is how it`s "Normally" done,,, & it`s been done that way forever & a day. The problem with the "normalllity" of heating the rod & chilling the pin to make the fitting effortless is that you then have no idea how tight they are stuck in there once it`s done that way. Now i`m not saying that it`s down right wrong to do it that way,,, just saying that once it is done that way, then how tight are the pins??? how do you know??? How do you check it without cold pressing them all to check how tight they really are fitted... Lets say (for example) that one rod is a bit bigger in the little end diameter, or maybe a tad oval, sightly distorted from a previous situation etc, & that pin is then looser than the others, Lets even suggest that it distorts in that very same heating process yeah???,,, well you`d have to cold press it to find out how tight they have all ended up yeah??? Not many engine reco shops actually check how tight they are once they`ve fitted them & they`ve cooled hey??? all you need is a tiny bend in a rod, add that to a loose(ish) gudgeon pin & it won`t be very long before you have railway lines down your bore. I cold press all mine & in doing so i can actually feel how tight they are while going in,,, if it`s loose then i fix the problem first & often have to swap the rod (or set of rods) to sort the problem. & yes, you need a special piston shaped base to press them on... The old guys used to use a big chunk of hardwood, these days i use various hard grey chunks of plastic shaped to suit, & yes they end up all stuffed & have to re-shape them all the time, but hey, you get that in the big city 
Just thought i`d add all that useless argumentative info, & If you diss-agree then too bad
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| Author: | 9YaTaH [ Fri Apr 27, 2007 6:27 pm ] |
| Post subject: | Reamer? |
TheMiniMan wrote: it`s quite funny really,,, sooo many people know how it`s "Normally" done,,, & re-read what i typed there--> "Normally" & i`m not bagging anyone here, no offence to anyone at all , truly!!!!! That is how it`s "Normally" done,,, & it`s been done that way forever & a day.
Get to the point Matt 
Ummmmm ......I would have thought most engine reconditioners would have run a reamer through the little end to check whats going on  Can you get oversize gudgeons 
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| Author: | drmini in aust [ Fri Apr 27, 2007 8:08 pm ] |
| Post subject: | Re: Reamer? |
9YaTaH wrote: TheMiniMan wrote: it`s quite funny really,,, sooo many people know how it`s "Normally" done,,, & re-read what i typed there--> "Normally" & i`m not bagging anyone here, no offence to anyone at all , truly!!!!! That is how it`s "Normally" done,,, & it`s been done that way forever & a day. Get to the point Matt Ummmmm ......I would have thought most engine reconditioners would have run a reamer through the little end to check whats going on Can you get oversize gudgeons Ummmmm......As it happens many moons ago I used to moonlight in an engine reconditioning shop (Acra Bores on Parramatta Rd). It's standard practice to measure the pins and rods for interference fit before assembly. It's also standard practice to cold press them out, that gives a first indication if things are bad. It is also common to heat the rod little end before fitting, this avoids the risk of piston damage if you cold press them and it misaligns. GR does it this way too. If you are still worried about interference fit after this, let it cool down to room temp and then use the press to move the pin slightly, read off the load.
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| Author: | glenno [ Sat Apr 28, 2007 4:01 am ] |
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Very good Dr Mini-thats bang on! Tho i'm in favour of heatiing the rods to the point whereby the pins are a very light tap fit-once the pin is home in position, you have pratically no physical way of checking whether or not the pin might have "picked-up" and formed small scratches and therefore ruining the pin-bore in the piston-personal preference i guess.. Temperature control on the rig is not a case of cooking it up and wanging it in-one I used was thermostatically controlled. Oh-and never had a pin walk in all my engines........no substitute for preparation!- and having the right gear.... |
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