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#6 Piston damage

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IowaTom View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IowaTom Quote  Post ReplyReply Direct Link To This Post Topic: #6 Piston damage
    Posted: Aug/29/2022 at 5:55pm
I may have found the source of the noise my engine was making.  While cleaning the pistons, when I got to #6 I see a piece of metal where I shouldn't be seeing it; poking up from the edge.  After pulling it, the compression ring falls apart and there's this lovely gash you can see here.
Hmm, I then went to the bucket that holds the pistons & rods I took out of a junker '58 OHV 6 I scavenged the OD tranny from.  The #6 from that engine has even worse damage in the same spot.  The others are fine.  That suggests to me perhaps the oil pump has weakened to where there's not enough lubrication back there.
(another reason I hate idiot lights in place of a gauge)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Aug/29/2022 at 6:11pm
IMHO a more likely cause would be detonation.  Carbon in the combustion chamber can create hot spots that induce knocking.   Knocking might be hard to hear from an old "loose" engine.  Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/29/2022 at 6:36pm
X2.
That's not an oil supply issue.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/29/2022 at 6:57pm
X3.
Detonation, but a round piece in that location also looks like ether used to start.
Detonation is usually the top edges to the top ring land and not that far down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Aug/29/2022 at 11:55pm
Detonation, possibly worsened by chronic cooling system issues. High mileage, crud collects towards the back of the 3ngine (I bet it's plugged back there) raising operating temperature, making effect of detonation worse there. 

I can attest that pinging can be hard to hear in this engine. 

Time for sn overhaul. Safe bet this isn't the only problem this engine has now. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IowaTom Quote  Post ReplyReply Direct Link To This Post Posted: Aug/29/2022 at 11:59pm
Yikes.  Sounds like it's time to pull it and do a major overhaul.  Thanks Guys.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinrev Quote  Post ReplyReply Direct Link To This Post Posted: Aug/30/2022 at 7:09am
And the 'far' cylinder on an old straight six is more likely to be running a little lean (just because of distance from the carb), and therefore a little hotter, and therefore more prone to detonation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote squirrel Quote  Post ReplyReply Direct Link To This Post Posted: Aug/30/2022 at 8:18am
Is the cylinder bore damaged? And how much wear is there in the bores?

it might be that you need a complete rebuild, or it might be that you can get away with a lot less, if you are tight for money and time, and don't need it to last forever. But that's a decision that you need to make based on a lot of info that we can only guess at...

like, you might be able to put one of the other piston/rod assemblies from the other engine into that cylinder, and run it that way for a while.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/30/2022 at 12:34pm
Others know these engines far better and if cooling is blocked at the rear to cause this then an engine flush, if possible would be in order also.
You have it stripped this far down, a rebuild is likely the better option.
Also, the 232 and 258's I've owned, to get even spark plug burn indications, used to put one level colder plug in #6 and sometimes #1. Don't know if this is available for these engines.
Even on Gen3 V8's running one heat range hotter/colder on some cylinders gives even burn indication.
Spark plugs tell you a lot of information about how an engine is operating and mixing and matching heat ranges to get even burn indications seems to make for a healthy engine, IMO.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IowaTom Quote  Post ReplyReply Direct Link To This Post Posted: Aug/30/2022 at 3:25pm
<<you might be able to put one of the other piston/rod assemblies from the other engine into that cylinder, and run it that way for a while.>>

That thought occured to me, too!  
I emailed a buddy who owns & operates a machine shop in nearby Renton (WA) and he said he had 31 engines ahead of mine and it looks like Feb of next year before he could take mine.  Crazy!

I'm going to (leisurely) pull the engine and disassemble it for a good block cleaning if nothing else.  I've considered a big tub filled with Purple Power.  :-)

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