Honing the cylinders - stock piston rings?

[JP50515]

Hey guys, so I will be honing the cylinders this week with a three stone honing tool that you chuck in a a drill. I need to order new piston rings and i'm not sure if I should be ordering the stock size or the first oversized rings.

Had oil in the cylinders, that's why i've got it torn down and just want to make sure I do this job properly.


Thanks

 

[yamaman]

To avoid wasting money, I (and my spidie senses tell me many others) would strongly advise you to take your cylinders and pistons to a machinest to have them measured. He will then advise the best course of action. Cheers

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[5twins]

That 3 stone hone isn't the best choice. If you're not careful and over do it, you can enlarge the bore. A bottle brush style or Flex Hone is a better choice for breaking the glaze. You might consider taking the cylinders to a shop for honing. It doesn't cost much and doesn't take long.

Have you measured the old rings to see just how worn they are? If the bores have some wear, new stock rings may still be out of spec. That would still be better than your old ones though because there's another aspect to rings - their tension against the cylinder walls. Old ones tend to lose this, new ones will have it all. First oversize is the other option. With those, you file them until they fit. With them, you can set the end gap to the minimum spec.

 

[JP50515]

I actually am in school for machining so you'd think I'd be able to do this in my sleep however I haven't started in the shop itself yet, just the classroom ha. I might bring em into class and give em to my professor lol

 

[5twins]

Measuring ring end gaps is simple. You remove them from the piston, stick them back in the bore, and measure the end gap with a feeler gauge .....

 

[yamaman]

An excellent practical assignment for you and your classmates!
Sorry 5twins, you are right of course, I was suggesting he measure bores and pistons to make sure they are in spec before ordering anything.
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[5twins]

Well, that is the proper way to do things. Checking the ring end gaps is just the 1st step to give you a general idea about the wear. Another quick but crude test is to stick the bare piston back in the bore and jam a feeler gauge between it and the cylinder wall. If you can get anything bigger than a .004" blade in there, you need pistons or maybe even a re-bore.

 

[JP50515]

what exactly are you measuring in that pic? the distance from one opening of the ring to the other? cuz mine are about a quarter inch wide and very loose on the piston

 

[weekendrider]

Yes the gap between the ends after the ring is compressed in the cylinder.

 

[JP50515]

aha! while compressed! That makes a lot more sense ha. Sorry I've got 3 finals at school today and my brain is just goin haywire

 

[XSLeo]

Taking them into class and use them as a learning tool for yourself and the class. Hands on is a very good way to learn. Just check with your instructer first, he may want to wait till you get to the shop. You may not want to wait.
Leo

 

[sseres]

Measuring ring end gaps is simple. You remove them from the piston, stick them back in the bore, and measure the end gap with a feeler gauge .....

What size feeler should you be able to get the ring gap that correlates with say original ring size being ok?

 

[weekendrider]

The oil ring is the largest gap .012-.035 in. The other two .008-.016 in.

 

[5twins]

Of the half dozen or so I've been into, I only found old rings still in spec in one. All the rest were worn beyond the spec and one had cylinder damage to the point of needing a re-bore. If I'm going to re-ring an old stock bore, I don't even bother with getting new standard rings, I get 1st oversize and file the end gaps to fit. Why put new rings in that are out of spec to begin with? And new standard size rings in a used bore usually are out of spec or very near the limit due to cylinder wear.

Hand filing rings is very tedious. I did it that way on the 1st engine I did the 1st oversize ring install on. Then one Sunday afternoon, I was watching a hot rod show on the Nashville Network. They were building a car motor and had to file rings to fit. They had a special tool to do it with. I tracked one down and just love it. So much easier than hand filing, simply place the ring on it and turn the crank .....

 

[glennpm]

Yeah, I figured with the hardness of the rings, that it would take forever to do by hand. After a lot of looking I bought one of these and intend on using it this coming weekend

http://www.speedwaymotors.com/Precision-Piston-Ring-Filer,2915.html

 

[weekendrider]

5twins
I'm up for adoption if you will let me play with your cool tools.
NO WAIT that didn't come across right.
Cool SHOP tools.

 

[5twins]

Yes, I'll admit I'm a bit of a tool junky, lol. I don't mind buying special tools. The more I use them, the cheaper they get, eventually paying for themselves. I've done about 6 twin top ends with this tool so far (3 BMWs and 3 650s). That's over 40 rings (oil rails on the 650 count as 2) so it costs me less than a dollar a ring. Big boys toys, lol.

 

[weekendrider]

What do you do for the wavy ring?
I know you've probably said in past posts but on 4 hrs sleep the gray matter is fuzzy.

 

[5twins]

I re-use the standard one from the old ring set. You can't clip, shorten, or file that expander ring and the 1st oversize one is too big. You have no choice but to re-use the original.