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Piston Install

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#1 plumbo1


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Posted 19 March 2020 - 04:51 PM

Hi all, Had the block rebored thay found a hole in one of the bores so had it relined to standard i brought a new (old stock pistons) std but the oil ring will not go in the bore put the old oil ring on and the piston go straight in would it be ok to use old oil rings any ideas, Cheers


#2 unburntfuelinthemorning


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Posted 19 March 2020 - 05:01 PM

Are you using a ring compressor?  Using old rings on a new bore would be slightly pointless.

#3 DeadSquare


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Posted 19 March 2020 - 05:32 PM

Put the new oil ring down the bore, so that the ends of the ring overlap.


Push the ringless piston down the bore to set the oil ring square in the bore.


Mark the lower end of the ring against the upper end and then remove it.


Grind or file the end of the ring down to the mark and check in the bore again.


The two ends of the ring should not quite touch.


This is called "Gapping the rings".


The gap depends on the size of the bore and road or racing use.

#4 Steve220


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Posted 19 March 2020 - 06:05 PM

Have you gapped the rings properly?

#5 Moke Spider

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Posted 19 March 2020 - 06:23 PM

You should never mix rings, even Oil Rings, from one type to another.


Ring Packs are designed as a set and mixing individual parts between different designs and types can have very bad results.


Your old Oil Rings will have likely lost much of their ability to control the Oil on the bores in any case.


Can you post up a photo of your particular Oil Rings so we can best advise the way forward here ?

#6 plumbo1


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Posted 19 March 2020 - 07:49 PM

thanks all for your replys i will do that tomorrow deadsqare, The rings were already fitted on the pistons  , Cheers for your reply's  :highfive:

#7 plumbo1


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Posted 19 March 2020 - 07:58 PM

Hi moke spider, I will try to post a photo of the rings tomorrow, Thanks for your help last time when I was trying to remove the torque converter, Cheers

#8 Cooperman


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Posted 20 March 2020 - 10:58 AM

With a ring in the bore and square with the bore, the gap between the ring ends should be 0.003" per 1" of bore diameter as a minimum.

So for a 1275 Mini, with a bore of almost 3", the gap must be a minimm of 0.009". You should find, and probably will, that most of the rings will gap at around 0.012" to 0.015" if they are modern pistons. I've not had to trim the ring ends on any new  rings for some long time, although a long time ago it was commont to have to do so. Manufacturing processes (CAM) have improved over the years.

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