Cause of this damage<experts needed>
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Joined: Jan 2002
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From: Windsor, Ontario, Canada
Cause of this damage<experts needed>
My friend just sent me some pics of what damage was on his dsm, he couldn't find any help anywhere else, so I told him I'd put it up here since there is alot of pro's on here. These's are 9:1 Wiseco's in 4g63 6olt, with maybe 2000miles max on the motor.
Engine was assembled by a local shop with a good rep., the owner of the car takes great care of the car, regular oil changes, good tuning, good break in, etc...
The rings basically never set, the compression went up and down alot, and he got sick of it and pulled the head to find this.
Any Idea's or opinion's? I have never personally seen a piston and scratched up above the top ring so I have no idea. Also the top rings are a bit seized in the grooves. 2 are like this and 2 are basically fine, he's gonna spec out everything this week to check for assembly problems, just though maybe we could get some insight before then...
Engine was assembled by a local shop with a good rep., the owner of the car takes great care of the car, regular oil changes, good tuning, good break in, etc...
The rings basically never set, the compression went up and down alot, and he got sick of it and pulled the head to find this.
Any Idea's or opinion's? I have never personally seen a piston and scratched up above the top ring so I have no idea. Also the top rings are a bit seized in the grooves. 2 are like this and 2 are basically fine, he's gonna spec out everything this week to check for assembly problems, just though maybe we could get some insight before then...
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Joined: May 2001
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From: Tallahassee, FL, US
Re: Cause of this damage<experts needed> (b18cx)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18cx »</TD></TR><TR><TD CLASS="quote">Looks like someone screwed up on the measurments during assembly, OR during break-in, it was running lean and the piston over expanded.</TD></TR></TABLE>
exactly. that is a sign of piston to wall clearances being too tight, either as measured by the machine shop or because of detonation and an overly excessive lean air/fuel mix
exactly. that is a sign of piston to wall clearances being too tight, either as measured by the machine shop or because of detonation and an overly excessive lean air/fuel mix
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Joined: Mar 2003
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From: Hudson, NH, 03051
Re: Cause of this damage<experts needed> (Alstare)
Looks like too much timing.If it was just to tight you would see the scuffing mostly below the rings on the the skirts.The scuffing at the top means it saw a lot of heat.The top of the piston is considerably smaller than the bore and even a couple thousands to small isn't a problem until the heat goes out of site.Rings will seat better if its a little lean as long as the loads are light.
Glenn
Glenn
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Joined: Jun 2004
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From: Seattle, WA
Re: Cause of this damage<experts needed> (NJIN BUILDR)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR »</TD></TR><TR><TD CLASS="quote">Looks like too much timing.If it was just to tight you would see the scuffing mostly below the rings on the the skirts.The scuffing at the top means it saw a lot of heat.The top of the piston is considerably smaller than the bore and even a couple thousands to small isn't a problem until the heat goes out of site.Rings will seat better if its a little lean as long as the loads are light.
Glenn</TD></TR></TABLE>
agreed
Glenn</TD></TR></TABLE>
agreed
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