WD Engine Overhaul Kits

Most pistons are worn out in the ring grooves.....too much up and down slop for the rings.

Also to add to dr. allis statements is after pistons have  had several hours of run time on them they usually measure smaller than original so unless the sleeves are undersized to be bored and honed to the piston size your ring seal with just new drop in sleeves will suffer due to the sleeve wall to piston skirt increased clearance  or piston slap. As power tech wrote also no replacement for displacement and more power is made from bore size than stroke because increased piston displacement increases airflow

Edited by mlpankey - 15 Jun 2010 at 8:26pm

Are you thinking  the old pistons shrinkage stops after first rebuild? once the material has been removed from the sleeve for a clearance on a new piston then it cant be added back for the shrinkage of old pistons and they are no guarantees 4 old pistons shrank the same amount.

I would be thinking that the piston would wear the same as the sleeve they are both getting used the same amount. They are replaced as an assembly for that reason.

Edited by Matt MN - 16 Jun 2010 at 2:17pm

.010 seems like a lot of wear. How many hours are you running to get that kind of wear? Makes me curious to see what the used pistons from my D262 compare to the new ones and what the new dimensions are supposed to be.

ml, if you installed a set of used 4.115 (4.125 new less .010 shrinkage) in a new set of sleeves, would the pistons wear again by .010 to 4.005? What's causing them to wear - don't the rings make the contact with the sleeve wall? Thanks for your help!

Thanks for the explanation. The graph of shrinkage vs cool/heat/cool cycles must drop off rapidly, else pistons would eventually shrink to nothing.

I understand what you're saying now. I'll bet the same pistons used in an engine that was only being worked at stock power demands probably wouldn't shrink near as much.

Brian report back with what your findings are on the D17d old piston skirt measurements to the new piston . I know cast pistons dont require as much clearance as forged but it would be of interest to me to know the variation. Also I would like to leave this subject with this thought. I am in the parts buisness I have 5.00 a hour with commision on sales order takers not really but play along with the thoughts. I sell a particular brand of piston /sleeve combo .I know the piston manufactorer recommended clearance and the sleeves are bored and finished honed to that clearance. Now you call just wanting to buy the sleeves my order taker needs to buy her child some school clothes. She ships four sleeves that has excessive clearance to you due to you using a different and maybe worn or shranked used pistons. Which will greatly reduce the time between rebuild to next tear down.

Edited by mlpankey - 17 Jun 2010 at 7:18am