Piston rings and cylinder bore steps

[andrew_27]

Evening all,

Im rebuilding a 1300 engine (more of a stripdown and reassembly really) and am in the stages of starting to assemble it again, im needing to put new piston rings on as some of the originals had broken when removing. I was intending on putting standard size ones on but i gather that the top rings need to be stepped due to the slight ridge formed at the top of the cylinder bore by the original rings and fitting a none stepped ring could cause it to break. Is this a part thats available or would the new top rings have to be machined/filed? thanks in advance for any advice!

[tony g]

Ive never heard of a stepped ring to clear the bore wear/step. I would hone the bore til the step was smoother and blended in and fit the normal rings.

Tony

[andrew_27]

cheers Tony, Ive honed the bores this afternoon and its definitely helped a bit. Im basically going off what it says in the haynes manual and the idea of busting a ring didnt appeal!

[Carledo]

Since the step is made by the limit of travel of the top ring, I can't see it making any difference if you fit another standard ring, it will still end its upward journey in the same place!
But if your bores are badly lipped and you have honed away the coke lip and some of the bore too, I expect it will smoke a bit, new rings notwithstanding!

Steve

[trackerjack]

I was of the understanding that the lip at the bore top should not be removed as this would cause smoking as Carledo suggests.
However I have seen and used ring dodger piston rings in the past and thay have a small portion removed during manufacture.

However as you are using new rings and have honed it will most likely be fine.

[andrew_27]

cheers lads, ive just lightly honed everything, i havent taken away the lips/steps as i thought that might be a bit excessive for what the honing tool is designed for. i did wonder however if its normal to have an ever so slightly recessed area under the lip/step (the dark grey part) as in the photo below...

[tractor boy]

Hi it's tractor boy. Stepped top rings used to be popular and available as ring dodgers many years ago. older car engines used to have more pronounced wear ridges at the top of the cylinder bore and fitting standard rings often resulted in rings breaking in service. Having said that I haven't seen them advertised for a long time. honing the bore should suffice providing the rige isn't too pronounced. Tractor boy

[tony g]

Were these stepped rings made by Chord or Cord? If so i heard of them as bore savers in the 80's but they ate away the bore too

Tony