EVO All Evo Model Discussion

Piston Question???

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Old Feb 21, 2020 | 10:01 AM
  #11  
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Originally Posted by 98hotrodfatboy
Definitely a bit of pepper on that porcelain.... As for the heads they're untouched. They look pretty much stock and definitely blew out a head gasket. Somebody was using OEM style head gaskets.. They should have went to an MLS. I think you'll be okay to get the heads worked. I don't understand why somebody would up the compression like that and not at least go to bigger valves doesn't make sense.. Because the combustion chambers look stock the squish was actually pretty big which probably helped create more detonation. You can have them worked no problem... You don't need to get another set of heads... But take them to your local Indy and let him make that decision but they look pretty good to me.. looks to me your damage is minimal so I would think a bore in a set of pistons and you'd be good to go..
Agree with this assessment.

For future reference, that peppering on the plug insulation is a classic sign of detonation so remember what that looks like. Catch it early and you can prevent major damage. Loud exhaust may mask the knocking sound but the plugs will tell the story if you know what to look for. Can't see the ground electrode but the color transition mark will also show if the timing was correct.

 
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Old Feb 21, 2020 | 10:53 AM
  #12  
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I don't think so Yankee Dog,the top of that piston would be all hammered to crap if it had swallowed something and the head would show damage from an object hammering around in there too. Whatever the case,allot of double checking should be done before reassembly. Don't want this one coming back again
 
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Old Feb 21, 2020 | 11:28 AM
  #13  
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Originally Posted by skills
I don't think so Yankee Dog,the top of that piston would be all hammered to crap if it had swallowed something and the head would show damage from an object hammering around in there too. Whatever the case,allot of double checking should be done before reassembly. Don't want this one coming back again
Yes, I agree, after I looked at the head pic I changed my mind. What threw me was the sharp edges of the defect. The pic Naz posted is a great pic of erosion with the gradual "eating away of the piston", but again, the original posters pic of his defect was sharp and irregular. Once I looked at the head pics, with nothing chewed up on the head, I was completely sold on the erosion. YD
 
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