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Wrist Pins

Roger Peterson

Registered User
Sweeny, Texas
I had rebuilt the top end 170 hr ago and the bottom had been about 500 hr.
I just split the case because I was starting to get some higher readings on Chrome. The lower end looked OK but #2 and #4 wrist pins had a lot of wear on them and they looked like they had been chrome. I have never seen a wrist pin wear out. Maybe the chrome broke up. Any one else got any ideas.
 
were the wrist pins still free floating in the piston? What location on the wrist pin was worn?
 
They were still free floating. The wrist pins had spring keepers in the pistons so they couldn't move but the wear seemed to be more under the rod. The rod oil holes were correct also.
 
wrist pin wear

Was it wear in the chrome on the wrist pin or
was it galling/spalling (transfer of metal from heat or lack of lubrication)

Usually the only things that would wear the wrist pin or rod bushings are:
1. Poor assembly procedures as in fit and clearances
2. Poor or substandard parts/materials
3. lack of lubrication
4. Or continued detonation in the cyl which is hard on wrist pin/bushings
5. You may be right about the chrome breaking up if it was a used wrist pin that was thin.
Pete
 
Re: wrist pin wear

polarpete said:
Was it wear in the chrome on the wrist pin or
was it galling/spalling (transfer of metal from heat or lack of lubrication)

Usually the only things that would wear the wrist pin or rod bushings are:
1. Poor assembly procedures as in fit and clearances
2. Poor or substandard parts/materials
3. lack of lubrication
4. Or continued detonation in the cyl which is hard on wrist pin/bushings
5. You may be right about the chrome breaking up if it was a used wrist pin that was thin.
Pete

It was just plane wear is what it looked like. It was only on cyl 2 and 4. They were new wrist pins. It could have been detonation but I have a full engine monitor and have always been running ROP and the pistons showed no sine of detonation. Maybe the oiler holes in the rods have a burr in them or something, havn't checked that, but the bearing holes and rod holes were lined up perfect. Had one once that the rod holes didn't line up with the bearing.
Have sent them off for evaluation so might get some insite. Just never had it happen before and hate to reasemble until I know what happened.
 
Never seen the spring wrist pin keepers on an A/C engine. Was it experimental. Don't they usually nickel plate wrist pins and then grind them or am I thinking of something else? I had a problem some years ago with rocker shaft bushings wearing on Superior rocker pins when the bushings were finished to the minimal tolerance. Opened them up to maximum for new parts and the wear went away. I suspect the final finish on the pin was to rough but couldn't get Superior to admit that.
 
Steve, these are forged pistons from Klaus Slaver at lightspeed. He builds racing engins and he said he had never seen a wrist pin failure. They were in a expermental 0-200. Posted here just to see if there had been many wrist pins found with bad wear patterns. I had never seen it. I think the chrome failed as I noticed a little rise in chrome on the last to oil changes.
 
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