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ibleedorange 
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Joined: 08 Feb 2010
Location: Harvard, IL
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 Topic: G Head Observation
Posted: 02 Feb 2025 at 1:48pm |
What do you think caused all the pock marks on the head? The piston looks good, but I'm sure they are not the originals. Only on 1 cylinder. Also found a little piece of 5/16" bolt with a offset hole in it lodged in one of the cooling ports. Most likely from an easy out, but what was it doing in there?
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RedHeeler79
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Location: NE Kansas
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Posted: 02 Feb 2025 at 2:27pm |
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Looks like that cylinder had water or coolant leaking into it, and sat that way for quite a while at some point in it’s long life.
Edited by RedHeeler79 - 02 Feb 2025 at 2:31pm
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ekjdm14
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Joined: 20 Aug 2024
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Posted: 02 Feb 2025 at 3:37pm |
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Agreed, looks like corrosion damage from water. What piques my interest though is the "tree rings" pattern barely visible on that part of the head. How high up do the pistons sit in a G? Wouldn't imagine the compression ratio was that high that it'd be a corroded impression of a piston sitting at TDC for years, so I'm wondering if it let a rod loose one time and the piston kissed the head?
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RedHeeler79
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Posted: 02 Feb 2025 at 4:02pm |
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The tree rings you’re seeing are marks from the cutter head on the surfacing machine at the machine shop. They used to leave a slight texture for gasket sealing, but with the newer MLS style gaskets they usually leave a more smooth, almost mirror like finish. —-on closer inspection, i see what you’re talking about, and it’s probably the area where the fire ring sealed against the head—- see that it follows around the combustion chamber
Edited by RedHeeler79 - 02 Feb 2025 at 4:05pm
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JoeM(GA)
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Posted: 02 Feb 2025 at 6:06pm |
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5/16 bolt piece was from a manifold stud into the water jacket someone was trying to get out
Edited by JoeM(GA) - 02 Feb 2025 at 6:07pm
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ekjdm14
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Posted: 03 Feb 2025 at 7:12am |
 RedHeeler79 wrote:
The tree rings you’re seeing are marks from the cutter head on the surfacing machine at the machine shop. They used to leave a slight texture for gasket sealing, but with the newer MLS style gaskets they usually leave a more smooth, almost mirror like finish. —-on closer inspection, i see what you’re talking about, and it’s probably the area where the fire ring sealed against the head—- see that it follows around the combustion chamber |
What I'm seeing is all through the pitted part of the head, not in line with the machining marks but perfectly concentric with where the bore would be & going all the way in to the center. That's why I thought maybe residue from a piston kissing it as the marks look just like the machine marks you see on the crown of a piston.
Like I say, barely visible but just in the area where the piston could've touched. You can see it better in the close up shot, easily missed on the first photo.
Edited by ekjdm14 - 03 Feb 2025 at 7:13am
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RedHeeler79
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Posted: 03 Feb 2025 at 12:26pm |
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I see that now… it does look like the machine marks in a piston crown of a flat-top piston. Your theory may be right. I’m assuming a G engine is not a power crater piston since the combustion chamber is in the cyl head. Never taken one apart. Perhaps ever so slight contact?
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