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05-19-2021, 11:35 PM
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#1 |
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Registered User
Join Date: May 2015
Location: Texas
Posts: 18
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5.3L Build Question
Tore down a 5.3l LM7 engine. Used a ball hone to de glaze cylinders and found this on one cylinder. Can't tell if it is a scratch or a crack. Anyone seen this before ?
Thanks Unknown miles in engine LS III Generation 
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05-20-2021, 07:24 AM
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#2 |
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Post Whore
  
Join Date: May 2015
Location: Alabama
Posts: 14,587
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Re: 5.3L Build Question
i wouldnt think a crack would be that straight....its not good whatever it is...whatd the rings look like ?...
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05-20-2021, 11:14 AM
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#3 |
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Registered User
Join Date: May 2015
Location: Texas
Posts: 18
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Re: 5.3L Build Question
The rings did not look bad. I had one cylinder that had stuck rings which caused lower compression, this was not that cylinder. Waiting on my bore gage to arrive before I go any further with that cylinder.
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05-20-2021, 01:54 PM
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#4 |
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driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,692
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Re: 5.3L Build Question
Looks like overbore time to me. 3.9" since you'll be in there anyways.
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05-20-2021, 04:10 PM
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#5 |
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Moderator
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,157
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Re: 5.3L Build Question
That looks like a top compression ring edge that has dug into the wall.....
Can you feel the scratch with your fingernail? If you can, time for a rebore. If you cant feel it with your nail, it may be ok to reuse as is.... If this is a street engine...no boost....and you are on a budget...rehone it and use it.... However... After honing, measure the skirt to bore clearance on the original pistons and if it exceeds 0.001 to 0.0015 (measure the pistons at the very bottom of the skirt at 90 degrees to the pin...) you should bore the engine....these engines use a short skirt piston skirt that makes these prone to rattles...they will rattle with anything more than 0.002..... Make absolutely sure the engine shop knows to keep the clearances to 0.001.... Make sure you gap the rings and then debur the ends of the rings gap with a small oil stone.... BTW,,,,that block should be decked before boring.... and dont forget to install new cam bearings...they will be used up.... 
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Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox 
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05-21-2021, 02:18 AM
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#6 |
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Registered User
Join Date: May 2015
Location: Texas
Posts: 18
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Re: 5.3L Build Question
Thank you for all this information.
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