detonation

papamoe on February 1st 2012, 5:32 pm

Just pulled a head off and found signs of detonation.My engine was missing a bit on the high end of rpm range and i tried several different things to cure it but never went away. Found one plug that was spotted but the rest looked good as they did when i changed them last.I have not pulled the pistons but the damage looks slight,most of what you can see is on the head.Its pitted above the exaust fly cut on the left,on the flat top of the piston and in the same place on the head.all of the exaust ports were chalky grey and sandy feeling. What the heck???

rmcomprandy on February 1st 2012, 5:35 pm

papamoe wrote:Just pulled a head off and found signs of detonation.My engine was missing a bit on the high end of rpm range and i tried several different things to cure it but never went away. Found one plug that was spotted but the rest looked good as they did when i changed them last.I have not pulled the pistons but the damage looks slight,most of what you can see is on the head.Its pitted above the exaust fly cut on the left,on the flat top of the piston and in the same place on the head.all of the exaust ports were chalky grey and sandy feeling. What the heck???

Once you get it apart, you can check the top ring groove width. It's almost certain that the top land has lifted some.

papamoe on February 1st 2012, 5:39 pm

Are you saying thats what caused the damage or the detonation caused the lifted land?

rmcomprandy on February 1st 2012, 5:48 pm

papamoe wrote:Are you saying thats what caused the damage or the detonation caused the lifted land?

NO ... that is probably going to be the result of mild detonation.

papamoe on February 1st 2012, 5:54 pm

I guess that will require new pistons.

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