new piston rings

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philip
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new piston rings

Post by philip » Thu Jan 10, 2019 8:25 am

just a followup on my piston ring project. the gaps on my old rings were .070 compression and .150 on the oil rings.
the rings are not worn thin so i am not sure what went on there. i ordered some .010 over rings from chaffins. i slid one
in the bore and it tight with no gap as it should be so i will grind the gaps to about .012 and install them. i have two sets of pistons
the ones that were in the car and a second set. the second set have tighter ring side clearance and generally are in better condition.
they do not have the oil drain holes that my other pistons have on the oil ring groove. i have received advice to drill these holes
and advice to not drill them so i dont really know what i am going to do. the issue to begin with is oil getting past the rings. philip


Adam
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Re: new piston rings

Post by Adam » Thu Jan 10, 2019 9:50 am

If there is much more than .002” clearance in the ring groove, it’s possible the new rings may still pump oil. If you don’t have the engine out, then replacing the rings and seeing what happens is the most logical course of action. If you have the engine out; then boring, honing, and properly fitting new pistons and rings will be your best course if action.


Scott_Conger
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Re: new piston rings

Post by Scott_Conger » Thu Jan 10, 2019 10:00 am

If you got advice to use pistons that had been modified with holes, to "fix" a problem 70 years ago, it wasn't very good advice.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!

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GrandpaFord
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Re: new piston rings

Post by GrandpaFord » Fri Jan 11, 2019 7:35 pm

Phil, All modern pistons have the holes in the oil ring grooves.
Attachments
Screen Shot 2019-01-11 at 7.33.20 PM.png
Screen Shot 2019-01-11 at 7.33.20 PM.png


Scott_Conger
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Re: new piston rings

Post by Scott_Conger » Fri Jan 11, 2019 10:16 pm

And that is all well and good for modern pistons with oil rings.

Model T's do not have oil rings. Just 3 compression rings.
Scott Conger

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kerry
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Re: new piston rings

Post by kerry » Fri Jan 11, 2019 11:31 pm

That being true, the original piston only had 3 compression rings but over the years many styles of replacements.
4 different oil ring styles, 3 different pistons with oil relief holes.
Attachments
cast piston+rings 005.JPG
cast piston+rings 004.JPG

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kelly mt
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Re: new piston rings

Post by kelly mt » Fri Jan 11, 2019 11:50 pm

I rebuilt a motor last year with iron pistons that had been drilled with six holes around the lower ring groove. In asking about this I was told that period racers did this. These were old standard size pistons. I wouldn't do that on a road car. I also found a set of pistons with the second groove drilled, again racers. PK


kerry
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Re: new piston rings

Post by kerry » Sat Jan 12, 2019 12:41 am

The oil relief holes in the centre and right pistons in the photo are below the second ring, drilled in a shamfer that is machined just under.

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GrandpaFord
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Re: new piston rings

Post by GrandpaFord » Sun Jan 13, 2019 2:45 pm

If the 3rd, or 4th, ring does not have the slots, then there is no need to have the holes in the pistons. If it does have the slots, then the holes should be drilled. If you don't have the slots then you don't have an oil control ring and all the rings are compression rings. The rings should be close fitting in the grooves and the gaps should be correct. The huge gaps that Phil reported will allow lots of oil to be pumped above the pistons. If the rings do not fit tight in the grooves then they will pump oil into the combustion chamber.

For my money I would change out to modern aluminum pistons with an oil control ring, but it is Phil's car and he gets to do what he feels is best. Aluminum pistons also means more work and money.

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Mark Gregush
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Re: new piston rings

Post by Mark Gregush » Sun Jan 13, 2019 10:55 pm

I looked at 5 more CI pistons, 5 that came from same engine, oil holes, the 5th, oil holes. So that makes 9 CI with oil holes.
I know the voices aren't real but damn they have some good ideas! :roll:

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