1987Comanche Posted November 25, 2012 Share Posted November 25, 2012 I started the autopsy on my old 4.0 tonight (will post other pics in the MJ project section tomorrow) but I found this and wanted to post it. WTF happened to the piston ring groove on #1???? The spot shown in the photo is roughly 2X the width of the rest of the PR groove Link to comment Share on other sites More sharing options...
JeepcoMJ Posted November 25, 2012 Share Posted November 25, 2012 Cylinder drag. How scored is the cylinder Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted November 25, 2012 Share Posted November 25, 2012 Cylinder drag. How scored is the cylinder But why? Ring installed upside down? Poor cylinder hone? Link to comment Share on other sites More sharing options...
JeepcoMJ Posted November 25, 2012 Share Posted November 25, 2012 Piece of debris probably in the wrong place at the wrong times time gouged the wall there...likely on a compression stroke. Link to comment Share on other sites More sharing options...
mountainman Posted November 25, 2012 Share Posted November 25, 2012 Make sure to take note of which cyl and positioning of where this was in/on the block. Cause machine shop will need to check in that spot for the most wear/max bore size. To determine how much needs taken out to get back to a circle. Many factors could have caused it but the main issue is what i just mentioned. Link to comment Share on other sites More sharing options...
1987Comanche Posted November 25, 2012 Author Share Posted November 25, 2012 I'll take a thorough look at #1 and see what it looks like. The engine is still upside down on the stand (need the harmonic balancer puller from Auto Zone) so I won't be able to look at the walls until tonight. This engine isn't being rebuilt but it is slated to become a coffee table at a friend's house :D . It's just as well. I think the #3 rod bearing spun and the #6 piston must have had a cracked piston skirt...it came out in 2 pieces. I put the other pics of the autopsy in the project section (see top of pg 2): http://comancheclub....-of-the-old-87/ Link to comment Share on other sites More sharing options...
1987Comanche Posted November 27, 2012 Author Share Posted November 27, 2012 I didn't find any corresponding gouges in cyl 1 that match the horrific wear on the top piston ring groove (see album in project section...I added pics). It seems like a section of the piston ring broke, stayed more or less in position, and wore the ring groove out. It's the only explanation I can think of but, as you can see, the engine was a mess! Link to comment Share on other sites More sharing options...
cz777 Posted November 27, 2012 Share Posted November 27, 2012 broken ring ? i have seen this with very heavy pinging and the other bad oil control - valve seals / rings etc Link to comment Share on other sites More sharing options...
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