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Author: Subject: piston rings
AndyGT

posted on 23/2/17 at 09:02 PM Reply With Quote
piston rings

Just been looking at this guide to fitting new piston rings:

www.duncanracing.com/TechCenter/4strk_ringinstall2-24-05.pdf

The rings I bought suggested using the wedge sided compression ring in the middle with "TOP" pointing up and a square edged compression ring as a top compression ring with manufacturers writing pointing up but the above link says the opposite!! : "wedged" ring to top of engine and squared to middle

Who is right?

If the rings were fitted incorrect (i.e. middle to top and top to middle), what would the consequences be?

btw, this is on a (c)20XE engine.





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r1_pete

posted on 23/2/17 at 09:19 PM Reply With Quote
That guide reads as for assembling motorcycle engines, last paragraph talks about sliding cylinders onto pistons, and makes no reference to using a ring compressor to facilitate fitting pistons into bores.

Go with the instructions on your rings, they should come individually packes with their location and orientation on the piston clearly marked, the only thing in that article of relavence is the 120 degree spacing of the gaps, which also need checking against manufacturers spec.

[Edited on 24/2/17 by r1_pete]

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perksy

posted on 23/2/17 at 10:12 PM Reply With Quote
Follow the instructions from the manufacturer of the rings, you won't go far wrong
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Slimy38

posted on 24/2/17 at 07:33 AM Reply With Quote
quote:
Originally posted by r1_pete
, the only thing in that article of relavence is the 120 degree spacing of the gaps, which also need checking against manufacturers spec.


I seem to remember reading somewhere that spacing is largely irrelevant as piston rings rotate and settle in a completely random position. It might be good practice to start with them evenly distributed but it's not essential.

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r1_pete

posted on 24/2/17 at 10:39 AM Reply With Quote
Yes Ive read that too, But as you say starting at 120 is seen as best practice.
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chillis

posted on 24/2/17 at 10:44 AM Reply With Quote
The 'wedge' shaped ring usually goes at the top as it is the 'ridge dodger' If these rings are being fitted in a freshly rebored cylinder then where the ridge goes doesn't matter, Indeed I would put the wedge in the middle on a fresh bore but it must go at the top for a 'used' bore that has only been glaze busted or the top ring will break first time you run it.

[Edited on 24/2/17 by chillis]





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