Home » Public Forums » GMCnet » Piston Ring End Gap (I know the specs are .010 - .023 but??)
| Piston Ring End Gap [message #224924] |
Tue, 08 October 2013 23:21  |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Hello Engine builders:
The Quick Questions are:
(Mahle Cast Rings)
A What are you experienced Builders Using for an end gap when installing your rings?? any problems in the .010 to .015 Range
B With our engines running harder and sometimes hotter, are you running larger gaps?? Most Ring Companies seem to be indicating .0145 as being minimum for a 4.156 bore such as mine. (.030 over) (4.156 X 0.0035 = 0.0145)
My engine destroyed a crank.  I have a pocket full of theories as to why the engine failed, but none could be substantiated. Unfortunately not knowing the exact cause is frustrating.
I found a core crank,and had it ground .010 under on the mains and throws. I also had the rotating assembly balanced. Luckily the cylinders were not damaged and a light hone made them good as new. (I'm happy I did not have to replace my nice forged pistons  )
Now that I finally have all the parts on hand, I can start building the engine again. Currently, I’m measuring about .012 to .014 ring end gaps. While these measurements are fine according to service manual specifications, they may be a little tight according to general knowledge.
Best Regards
John Heslinga
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: Piston Ring End Gap [message #224994 is a reply to message #224924] |
Wed, 09 October 2013 13:57  |
Cadillackeeper
Messages: 464
Registered: October 2012
Location: Fort Lauderdale
Karma: 1
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Senior Member |
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I would check with the Piston manufacturer.I have the KB hypers in my Cad and its a crazy huge file fit end gap they use,no matter the ring manufacturer.Forged is most likely tight.
77 455 Elaganza II and 67 Animal, Built 500 Powered Eldo
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| Re: [GMCnet] Piston Ring End Gap [message #225005 is a reply to message #224924] |
Wed, 09 October 2013 15:35 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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John, I use .004" per inch of bore. Example: 4 inch bore x .004 = .016".
You do not want the ends of the rings to expand to the point where they
touch. Bad stuff happens then. You can go a scosche tighter than that on
the second ring, but not much. Remember, if an appropriate amount of
lubricant does not reach the top ring, bad stuff will surely follow.
Jim Hupy
Salem, Or
78 Gmc Royale 403
On Oct 8, 2013 9:21 PM, "John Heslinga" <rbeeper@hotmail.com> wrote:
>
>
> Hello Engine builders:
>
>
>
> The Quick Questions are:
>
> (Mahle Cast Rings)
> A What are you experienced Builders Using for an end gap when installing
> your rings?? any problems in the .010 to .015 Range
>
> B With our engines running harder and sometimes hotter, are you running
> larger gaps?? Most Ring Companies seem to be indicating .0145 as being
> minimum for a 4.156 bore such as mine. (.030 over) (4.156 X 0.0035 =
> 0.0145)
>
> My engine destroyed a crank. :x I have a pocket full of theories as to
> why the engine failed, but none could be substantiated. Unfortunately not
> knowing the exact cause is frustrating.
>
> I found a core crank,and had it ground .010 under on the mains and throws.
> I also had the rotating assembly balanced. Luckily the cylinders were
> not damaged and a light hone made them good as new. (I'm happy I did not
> have to replace my nice forged pistons :d )
>
> Now that I finally have all the parts on hand, I can start building the
> engine again. Currently, I’m measuring about .012 to .014 ring end gaps.
> While these measurements are fine according to service manual
> specifications, they may be a little tight according to general knowledge.
>
> Best Regards
>
> John Heslinga
> --
> John and Cathie Heslinga
> 1974 Canyonlands 260
> TC4W "Too Cool For Words"
> Retirement Projects Galore
> Edmonton, Alberta
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: Piston Ring End Gap [message #225025 is a reply to message #224924] |
Wed, 09 October 2013 20:19 |
Cadillackeeper
Messages: 464
Registered: October 2012
Location: Fort Lauderdale
Karma: 1
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Senior Member |
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Nice!!!!!Looks like instructions,makes me want to rebuild another.It has been over 7
years.I did have tons of oil going by for a long,time before things finally set in.I was
unaware of the hyper piston failures,mostly from nitrous,racing stuff and heavy detonation.I guess pulling a giant Motorhome is similar.Forged pistons he going to run for years to come.
77 455 Elaganza II and 67 Animal, Built 500 Powered Eldo
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| Re: Piston Ring End Gap [message #225093 is a reply to message #224924] |
Thu, 10 October 2013 16:33 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Not sure what article you are referring to or what it says. However:
In Joe Mondello's article in the Engine Builders Magazine, he states :
| Quote: |
I end gap my rings wider than most rebuilders. The top ring on a 4.125” to 4.155” net bore is .020” to .022” top .022” to .024” second oil ring rails .020” to .022”.
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This sure indicates to me that it was a good thing I'm asking. The .010 spec sure could be a problem. I'm feeling a lot more comfortable now. Thanks
I don't know how i can cryogenically freeze my block though :>]
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] Piston Ring End Gap [message #225184 is a reply to message #224924] |
Fri, 11 October 2013 07:09 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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I hand fit each ring to the cylinder it is destined for. To measure, I use
the piston to push the ring down into the bore 1" and use a feeler gauge
for measuring. I have a manual ring gap grinder and when I get the ring to
what the mfr recommends, I carefully finish the ring gap edges with a
stone. I also follow the mfrs recommendation for ring placement on the
piston.
Steve F.
On Tue, Oct 8, 2013 at 9:21 PM, John Heslinga <rbeeper@hotmail.com> wrote:
>
>
> Hello Engine builders:
>
>
>
> The Quick Questions are:
>
> (Mahle Cast Rings)
> A What are you experienced Builders Using for an end gap when installing
> your rings?? any problems in the .010 to .015 Range
>
> B With our engines running harder and sometimes hotter, are you running
> larger gaps?? Most Ring Companies seem to be indicating .0145 as being
> minimum for a 4.156 bore such as mine. (.030 over) (4.156 X 0.0035 =
> 0.0145)
>
> My engine destroyed a crank. :x I have a pocket full of theories as to
> why the engine failed, but none could be substantiated. Unfortunately not
> knowing the exact cause is frustrating.
>
> I found a core crank,and had it ground .010 under on the mains and throws.
> I also had the rotating assembly balanced. Luckily the cylinders were
> not damaged and a light hone made them good as new. (I'm happy I did not
> have to replace my nice forged pistons :d )
>
> Now that I finally have all the parts on hand, I can start building the
> engine again. Currently, I’m measuring about .012 to .014 ring end gaps.
> While these measurements are fine according to service manual
> specifications, they may be a little tight according to general knowledge.
>
> Best Regards
>
> John Heslinga
> --
> John and Cathie Heslinga
> 1974 Canyonlands 260
> TC4W "Too Cool For Words"
> Retirement Projects Galore
> Edmonton, Alberta
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Take care,
Steve
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