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Trnelson

.01 Ring with Standard Piston

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A little background.  I picked up my 71 240 last summer for a new hobby.  It is not a DD, race car or show car in the near future.  One of the reasons I bought it was to do a complete tear down and assembly on a fairly simple engine.  I pulled the motor and have torn down, cleaned, re-finished most all parts and I'm ready to re-assemble.  I have learned a lot and have a much more through understanding of how the engine works and how modifications impact all aspects of performance.  Knowing what I know now I do want to eventually have the block and head professionally machined with all new or machined components.  However, at this point in my new hobby I've about hit my spending limit for the short term. I ordered standard rings and bearings for the refresh and I am .003”out of tolerance on the rings. I know that for the best result and long term reliability the head and block should go to a machine shop.  My question is:   knowing that the car will only see 2-3,000 miles per year, with plans for a full on rebuild within 2 years would it be best to use the standard rings knowing that there will be some compression loss and blow by, probably about the same as before, or is it possible or make sense to pick up a set of .01 over rings and file them to fit within the .030- .045 spec.  There is no ridge at the top of the bore and the .003”out seems to be consistent  from top of the stroke to the bottom indicating very little if any taper.  I would like to see some improvement from all my efforts but absolutely do not want to create headaches down the road.  

 
 
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Thanks for the input

 

Tom

Edited by Trnelson

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26 minutes ago, Trnelson said:

I ordered standard rings and bearings for the refresh and I am .003mm out of tolerance on the rings.

 

26 minutes ago, Trnelson said:

pick up a set of .01 over rings and file them to fit within the .030- .045 spec

What do you mean by "out of tolerance"?  End gap?  And do you really mean .003 millimeters?  That is a tenth of a thousandth of an inch. .0001 inches.

Is the bore oval'ed?  That's the other measurement you want to take.  

If you're only planning a few thousand miles on it you might be best to buy rings that will seat quickly.  Some ring materials would probably still be breaking in by the time you rebuild it again.  And I think that there are tricks to get a quick break-in, at the expense of longevity.  A rough hone finish, for example.  Not an expert, others know more.

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I edited the original post to reflect inches not mm, my mistake. Yes, I am referring to the ring end gap. I’ll need to check on how oval’ed they are. Interesting thought on quicker break-in procedures, I’ll do some research on that. 
 

Thanks

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I used cast iron rings with a quick/rough hone on my 2.8 block. My machinist and the internet instructed me to do down hill lower gear foot off the pedal. It sucks the rings to the cylinder walls for faster seating of the rings. The other is up and down rpms for short amounts of time, nothing steady too long. That car runs great and had solid numbers on all 6 when I did a compression check years ago. 165 I think?

On my 2.4 I used chrome faced moly rings with a specific hone for those rings. 83mm rings are hard to find without spending big bucks so I got Hastings from my machinist. I've never checked the compression on that motor but it runs so good I don't want to. :victorious:

I would stop by and talk to a machinist, they don't like talking on the phone, it's a waste of time for them. Machine work on these L motors is very basic, not too expensive. You need to find an older shop. They quit making these in 1984 but an older guy will say he's worked on thousands and would have to remember what to do. My best advice, if you haven't already got it, would be buy this book and read it 3 or 4 times. I was able to to rebuild mine without knowing anything about car motors.

https://www.amazon.com/gp/product/1931128030/ref=dbs_a_def_rwt_hsch_vapi_tpbk_p1_i3

61XQ92jjQ1L._SX373_BO1,204,203,200_.jpg

 

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is your current ring end gap 0.049"? thats 1.2mm, which is very big. 

my recollection of the spec is around 0.3 to 0.4mm for the top ring. 

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http://www.kangamotorsports.com/blog/setting-ring-gaps

 

Piston and piston ring manufacturers provide specification for their ring gaps dependent on the performance application. These are normally specified as a gap times by the cylinder bore diameter.

For our high performance street applications these were our values:

  • Top Ring = Bore x 0.0045 = 3.4855 x 0.0045 = 0.0157 inches

  • Second Ring = Bore x 0.0050 = 3.4855 x 0.0050 = 0.0174 inches

  • Oil Ring > 0.015 inches

Given that we can only measure to 0.001 inches with our feeler gauges we rounded up or down the values to:

  • Top Ring = 0.016 inches

  • Second Ring = 0.017 inches*

  • Oil Ring > 0.015 inches

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29 minutes ago, jonbill said:

is your current ring end gap 0.049"? thats 1.2mm, which is very big. 

my recollection of the spec is around 0.3 to 0.4mm for the top ring. 

3.4855. That's a darn good recollection. :beer:

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My amateur strips are showing!  Took some more measurements this afternoon. So with the new standard rings installed to a depth of 2.5” I’m getting anywhere from .48mm to .53mm end gap. Monroe’s Manual says anything over .43mm get new rings. I understand that with this much discrepancy I will have to bore it out to get it right. My long term plan is to do a complete high quality, comprehensive build and now that I’m learning more about how everything works I’d like to take the time to figure out exactly what I want and how to get there. 
My question is has anyone tried a .01” oversized ring, filed down and used short term to make up for the worn items without causing any severe damage. I know that it used to be fairly common practice to get a “plus 10” ring job as a stop gap measure, I just haven’t found anything on anyone doing it on these motors. 

I realize it seems stupid to be this far in and not “go all the way” but this is my trial run project and I’ve already overshot the runway on expenses for the short term. The next go around will be much easier as I have most all of the tools and more experience to make educated decisions.   I’m really enjoying the process and look forward to building one without cutting any corners.  
@siteunseen I do have the book and it’s a great resource for sure. One issue I do have is that I live in the middle of nowhere and there are no quality machine shops within 1.5 hours from me. 

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If it says anything over .43 get new rings I'm not thinking you should bore the cylinders, just get new rings. Maybe I'm not understanding but that's not unusual so I apologize if I'm simplifying too much. You think you live in the middle of nowhere! LOL I have one machine shop and one machinist. His brother does exhaust work.

Anyhow, don't do like I did and over think yourself to pieces. These are simple compared to most motors and you have a lot of guys just waiting to help here. It's cold out and we are sick of the news on television. PLEASE give me something Z related to talk about! 

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The first thing that I'd do is to stop mixing your measurement systems together.  Pick metric or pick standard but pick just one.

What size are the pistons?  Rings, pistons and cylinders all need to work together.

I'd try one of the oversize rings, fit it, and see how it fits the bore.  If your bore is ovalized (you never answered that question) then it's probably equally bad to use an oversize ring gapped down as a "proper" ring with a big gap.  They're both round rings in oval bores.  Most of the blowby will come from the poor seal in general, not the larger gap.

You might just fit one oversize ring, stick it in the bore and shine a bright light around the edges.  If it's a poor fit you'll see light shining through.

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Those are the measurements from new standard size rings.  Wondering if .01 over rings would be a feasible option to take up the slack short term. 
Trust me, I’m isolated in the mountains!  I see you’re in Bama my family is from Anniston which is considered HUGE compared to my current location!  Highlands, NC pop 968

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Are you kidding me? You want to install .010 inches ( .25 mm) oversized rings on a standard piston? Never heard of anyone doing that, but am sure that would probably be a disaster! Get the cylinders honed at a machine shop, install standard rings on your cleaned up standard pistons and your gaps will be correct. IMHO

Edited by Diseazd

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I know they would have to be filed down to get the right gap.  I've read that this used to be common practice on older engines.  Obviously I have zero experience with it but it seems to me that if the target gap is .030 - .043 and as it stands now with new standard size rings set in the bore my gap range is .48 to .53  The oversized rings are .25mm larger then it would require filing off .07-.02 to get to the .030 gap.  I would want to cheat that up to probably .035 to be safe on the bottom end of the stroke.

Current gap= .53 with standard ring, .28 with a .25 larger ring so file off .07 to get .030

I am assuming that the .25mm oversized ring is the same thickness as standard and will fit in the standard piston

Quote from an AACA forum:

"Typically every cylinder is bored because it incresases displacement, and possibly piston weight. Not always. It was not uncommon in the old days to fix one cylinder by overboring. A one-cylinder fix today usually involves sleeving the really bad cylinder to match the good ones.

.010, .020, etc are piston and bore oversizes. An .020 piston ring goes on an .020 larger piston in an .020 larger bore.

If a bore has wear it is possible to put in larger rings to compensate for wear, to some small extent. These are called "File-Fit" rings. They are made just a little too long and you file the ends to get the ring gap where you want it. They can be used in new engines when trying to get the ring gaps absolutely perfect (for racing, etc.). In old engines they can be used to make the wear situation a little less bad.

The limitation is that worn bores have taper, and if a ring gap closes when hot, the ring breaks and it destroys everything in sight.

You have to set the gap at the bottom of the bore (the least worn part), because the gap is tightest there. The part that matters most to the ring's function though is the top, and the top is more worn. No matter what you do the ring gap at the top of the bore will be too loose, it will just be a little less loose than if you had just put standard rings in. It helps, but is no substitute for a rebore and new pistons.

People used to also knurl pistons to compensate for piston skirt and bore wear, to keep them from slapping and making noise.

For the most part, nobody does this stuff anymore."

 

I'm probably way overthinking this and will spend a lot of time for very little gain...  Such is my life 🙃

Edited by Trnelson

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5 hours ago, siteunseen said:

Okay, you got me now. LOL

If Anniston is considered huge you are isolated.

Yea right! FYI if you don't already know Anniston is home to the best pizza place in the southeast.

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38 minutes ago, Trnelson said:

Yea right! FYI if you don't already know Anniston is home to the best pizza place in the southeast.

The guy I work for here in Gadsden is from Anniston. His family has had bbq restaurants since the 60s. The Goal Post was the first now they have Betty's BBQ. I work at Pruetts BBQ. Not familiar with the pizza shop you're speaking of because I always eat for free at Betty's. LOL

I'm 40 minutes north, up hwy 431. What's the name of the pie slingers place?

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16 hours ago, Trnelson said:

 So with the new standard rings installed to a depth of 2.5” I’m getting anywhere from .48mm to .53mm end gap. Monroe’s Manual says anything over .43mm get new rings.

He said the new rings, unmodified, have a gap that is too big.  Honing won't make the bore smaller, and you can't file a ring end to make it smaller.  Cut it twice and it's still too small applies here also.

I wonder if the pistons aren't already one size over.  There are no piston measurements here.  You kind of just need to get all of the measurements and figure out the best combination.  For just a few thousand miles a year, you could probably just hone and put the big gap rings in and be fine.

3 hours ago, Diseazd said:

Are you kidding me? You want to install .010 inches ( .25 mm) oversized rings on a standard piston? Never heard of anyone doing that, but am sure that would probably be a disaster! Get the cylinders honed at a machine shop, install standard rings on your cleaned up standard pistons and your gaps will be correct. IMHO

 

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26 minutes ago, siteunseen said:

The guy I work for here in Gadsden is from Anniston. His family has had bbq restaurants since the 60s. The Goal Post was the first now they have Betty's BBQ. I work at Pruetts BBQ. Not familiar with the pizza shop you're speaking of because I always eat for free at Betty's. LOL

I'm 40 minutes north, up hwy 431. What's the name of the pie slingers place?

I remember The Goal Post, used to have the neon football flashing through the uprights!  Mata's Pizza not too far down Quintard from where the Goal Post used to be. Try it sometime, I'll be willing to bet you will love it.

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1 hour ago, Zed Head said:

He said the new rings, unmodified, have a gap that is too big.  Honing won't make the bore smaller, and you can't file a ring end to make it smaller.  Cut it twice and it's still too small applies here also.

I wonder if the pistons aren't already one size over.  There are no piston measurements here.  You kind of just need to get all of the measurements and figure out the best combination.  For just a few thousand miles a year, you could probably just hone and put the big gap rings in and be fine.

 

I will re-check the piston size this evening but if memory serves me they are 83mm

I must be missing something but it seems to me that if you file both ends of a ring equally you could make it smaller when compressed.  I'm looking at a manual ring filing tool on Amazon and it seems easy enough to use, just take little bites and keep checking

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You said the gap was too big when using new unmodified standard rings.  Honing won't make the gap smaller, it will make it bigger.  I was replying to Diseazd's comment.  He said to just hone and use standard parts, but you already tried standard parts.  That was your original point.

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38 minutes ago, siteunseen said:

Damn that brings back memories.  We would travel from KY to AL every Christmas, when I saw that I knew we were close to Grannie's house!  Glad its still glowing strong

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4 minutes ago, Zed Head said:

You said the gap was too big when using new unmodified standard rings.  Honing won't make the gap smaller, it will make it bigger.  I was replying to Diseazd's comment.  He said to just hone and use standard parts, but you already tried standard parts.  That was your original point.

Ah, sorry  I got all caught up talking about restaurants in Central AL and thought you were replying to me.  More measurements coming soon and as far as your question regarding oval shaped bores, they don't seem to be oval as the gap is consistent regardless of orientation within the bore.

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It's been a long time since I've been up that way.

Beautiful area but not close to anything

Blown budget or not, I probably wouldn't pursue this path. It's pretty cheap to have a block machined.

The piston rings are a wash either way but you would need new pistons. You need new bearings any way, so it doesn't add a lot of cost to just go ahead and redo the lower end right. If you try to do what you are suggesting you will end up paying twice to do basically the same work

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