Adjusting piston rings??

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malcolm
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#1 Adjusting piston rings??

Post by malcolm » Sat Dec 01, 2018 10:54 am

I was Idly reading my Haynes workshop manual, when I read this:
"When a new piston ring is brought into use it's gap, when sprung out in the cylinder bore, must be measured and adjusted as necessary"

There is then a table of what the gaps should be.

But how do you "adjust" a piston ring? Surely rings are just a certain size, and either fit with the right gap or don't?
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S

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Durango2k
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#2 Re: Adjusting piston rings??

Post by Durango2k » Sat Dec 01, 2018 10:59 am

Well, in the old days, you could buy a size, and without drilling the cylinder it would have been too large, or its gap too small.

You‘d then use a file to make it fit.

Nowadays, new cylinder diameter, new piston means a fitting diameter from scratch.

Be sure to get the orientation correct, 120 deg apart is the rule.

Carsten
Jag E '66 S1 2+2, Citroen DS 23 Pallas iE, Citroen SM 3.0, Concept Centaur MK1, Citroen 11 BL '54, Sinclair C5, Velosolex

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#3 Re: Adjusting piston rings??

Post by malcolm » Sat Dec 01, 2018 11:07 am

ok, thanks Carsten, I understand now
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S

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JerryL770
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#4 Re: Adjusting piston rings??

Post by JerryL770 » Tue Dec 11, 2018 7:34 pm

You should find the necessary gap detailed in the workshop manual. It will vary from engine to engine depending on use and cylinder bore.

Even with a re-bored engine and new pistons, you should carefully remove the rings and 1 by 1 insert them into the bore making sure they are straight by aligning them using the piston, then measure the gap with feeler gauges. The rings are mostly cast iron and the ends can be filed easily with a fine file. Better a little loose rather than tight.

If fitting new, stepped top rings in and engine with wear (no re-bore) the piston rings should be gapped at the bottom of the bore where there is less wear.
Jerome Lunt
1970 S2 FHC - Dark Blue, Red Interior, MX5 Seats

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#5 Re: Adjusting piston rings??

Post by malcolm » Wed Dec 12, 2018 9:34 am

Thanks Jerome!
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S

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christopher storey
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#6 Re: Adjusting piston rings??

Post by christopher storey » Wed Dec 12, 2018 10:37 am

The modern piston manufacturers seem to take the view that no gapping is now needed. Presumably the machined tolerances are now much more accurate than was the case 60 years ago

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Series1 Stu
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#7 Re: Adjusting piston rings??

Post by Series1 Stu » Wed Dec 12, 2018 10:19 pm

That's probably true, but you'd want to check it anyway. Wouldn't you?

Regards
Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
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#8 Re: Adjusting piston rings??

Post by Durango2k » Wed Dec 12, 2018 10:23 pm

Yes, but for the risk of taking them off? Usually its a re-bore anyway, and then they will fit.

Carsten
Jag E '66 S1 2+2, Citroen DS 23 Pallas iE, Citroen SM 3.0, Concept Centaur MK1, Citroen 11 BL '54, Sinclair C5, Velosolex

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#9 Re: Adjusting piston rings??

Post by Series1 Stu » Wed Dec 12, 2018 10:28 pm

I get what you mean but if someone can't sensibly remove them then they shouldn't be rebuilding an engine.

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Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
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'94 X300 XJR basket case

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