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top ring puzzle

General engine tech -- Drag Racing to Circle Track

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alotadust
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top ring puzzle

Post by alotadust »

4.020 piston, 1/16-1/16- 3/16 plasma rings
went to install in block, and top ring won't compress enough, about .010 hangs out,
I did file fit, and installed in the block by them selves, no problem .021 end gap
measure ring depth ( ring width or how deep it is)
top .183
2nd .178

measured piston ring depth
top .160
2nd .181

these are forged SBC from speedmaster,
as are rings,

should I cut the ring land deeper on the lathe? if so, how much?

yes, I'm thinking you get what you pay for, LOL
never experienced this before, ( 1st time using speedmaster also)
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Re: top ring puzzle

Post by Tom68 »

alotadust wrote: Tue May 24, 2022 6:46 pm 4.020 piston, 1/16-1/16- 3/16 plasma rings
went to install in block, and top ring won't compress enough, about .010 hangs out,
I did file fit, and installed in the block by them selves, no problem .021 end gap
measure ring depth ( ring width or how deep it is)
top .183
2nd .178

measured piston ring depth
top .160
2nd .181

these are forged SBC from speedmaster,
as are rings,

should I cut the ring land deeper on the lathe? if so, how much?

yes, I'm thinking you get what you pay for, LOL
never experienced this before, ( 1st time using speedmaster also)
Can't imagine how you'd ever get the piston clocked up good enough for a second cut.

Get Speedmaster to supply matching components.

Had a crank ground once and the thrust was some ridiculous size. Asked grinder to supply bearings to suit, he says unavaliable, pointed out he ground the crank, he found bearings to suit.
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Re: top ring puzzle

Post by Walter R. Malik »

alotadust wrote: Tue May 24, 2022 6:46 pm 4.020 piston, 1/16-1/16- 3/16 plasma rings
went to install in block, and top ring won't compress enough, about .010 hangs out,
I did file fit, and installed in the block by them selves, no problem .021 end gap
measure ring depth ( ring width or how deep it is)
top .183
2nd .178

measured piston ring depth
top .160
2nd .181

these are forged SBC from speedmaster,
as are rings,

should I cut the ring land deeper on the lathe? if so, how much?

yes, I'm thinking you get what you pay for, LOL
never experienced this before, ( 1st time using speedmaster also)
Buy a good set of rings with the proper depth dimension.
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Re: top ring puzzle

Post by PRH »

The “standard” D wall radial thickness for a 4.020 bore is .183”...... so the problem is the pistons don’t have a “standard” ring groove depth.

Normally I’d say it wouldn’t be an issue to source some .155 radial thickness rings...... but these days it might be a little tuff.
Make some calls.
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Re: top ring puzzle

Post by 1972ho »

Just call Keith at Total Seal he will sell you the proper ring for the pistons just give him the depth if you only need the top rings you can just get those.
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Re: top ring puzzle

Post by ProPower engines »

alotadust wrote: Tue May 24, 2022 6:46 pm 4.020 piston, 1/16-1/16- 3/16 plasma rings
went to install in block, and top ring won't compress enough, about .010 hangs out,
I did file fit, and installed in the block by them selves, no problem .021 end gap
measure ring depth ( ring width or how deep it is)
top .183
2nd .178

measured piston ring depth
top .160
2nd .181

these are forged SBC from speedmaster,
as are rings,

should I cut the ring land deeper on the lathe? if so, how much?

yes, I'm thinking you get what you pay for, LOL
never experienced this before, ( 1st time using speedmaster also)
Do you have the bores chamfered well enough to allow the rings to slide into the bore without hanging at the top??
Also looking at your ring measurements is it the 2nd ring that will not go into the bore??
Or are the rings installed in the wrong grooves??

When the rings are installed on the piston how much hangs out of the grooves???
and what is the diamention of the pistons in the ring land area compared to the skirt??That area should be about.020-.030 smaller in diameter to allow for expansion of the top of the piston ring area.

Are all the ring grooves the same depth?? As in all the top and 2nd grooves measure the same depth?
They may be mis-machined at the factory and depending on what ring was supplied it may be as simple as changing the rings in question.
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Re: top ring puzzle

Post by BillK »

dust,
Like the others have said you simply have the wrong set of rings. You need a set of shallow groove rings. I would pick up the phone and call Speedmaster and see what they say. Also are you sure they are not supposed to be metric rings ? I have used a couple of sets of their pistons and I am pretty sure both were 1.5mm 1.5mm 2.5mm
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alotadust
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Re: top ring puzzle

Post by alotadust »

the rings are speedmaster, for this application, (supposedly)
they are actually 1.5/1.5/ 2.5mm
I provided the actual measurement, (I'm old and no need to learn metric, LOL)

thx for the input,
I feel a call is 1st,
then see what I need from there,
again thx!
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Re: top ring puzzle

Post by leahymtsps »

If need be, you can send the top ring to TS and they can back cut them to
the proper depth.

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Re: top ring puzzle

Post by BillK »

alotadust wrote: Tue May 24, 2022 9:50 pm they are actually 1.5/1.5/ 2.5mm
I provided the actual measurement
Actually there is almost .003" difference between 1/16 and 1.5 mm

alotadust wrote: Tue May 24, 2022 9:50 pm (I'm old and no need to learn metric, LOL)
I'll be 72 in a month and have been using metric since high school. Metric rings have been around for a loooong time.

Never too old to stop learning :) :)
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Walter R. Malik
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Re: top ring puzzle

Post by Walter R. Malik »

BillK wrote: Wed May 25, 2022 6:51 am
alotadust wrote: Tue May 24, 2022 9:50 pm they are actually 1.5/1.5/ 2.5mm
I provided the actual measurement
Actually there is almost .003" difference between 1/16 and 1.5 mm

alotadust wrote: Tue May 24, 2022 9:50 pm (I'm old and no need to learn metric, LOL)
I'll be 72 in a month and have been using metric since high school. Metric rings have been around for a loooong time.

Never too old to stop learning :) :)
Ford Motor Company has used them in their 5.0 liter and other 4.000" bore engines since the 80's.
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Re: top ring puzzle

Post by Momus »

I've done similar to this many times

My lathe has bolt on jaws and I make a set of aluminium dummy jaws and turn them in-situ to the oil ring width to hold the piston true. The jaws will have a fair bit of stand off- you might need spacers.

Use an insert or steel cutter well relieved and narrower than the ring land, and with very good lighting get your depth and then your width without with drawing the tool to minimise the chance of inadvertently cutting the ring land oversize.
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Re: top ring puzzle

Post by Dan Timberlake »

If we can believe the on-line info, modern ring groove finishes and accuracy are way beyond what most mortals can hope to achieve with turning tools even in a Hardinge tool room lathe.
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Re: top ring puzzle

Post by blykins »

I stopped reading at "Speedmaster".
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alotadust
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Re: top ring puzzle

Post by alotadust »

must be nice to afford name brand( and prices)
but most people can't,
so I do with what I can afford, (some folks should just remain silent, rather than remove all doubt )

I did source a top ring from total seal,

found out early viper V10 used same ring set up,

beside radial width,
had to be aware of axial width,

learn something every day,

could of bought some from summit ,etc
but knew TS was correct,
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