- Joined
- Feb 17, 2009
- Messages
- 16,719
- Reaction score
- 15,989
- Location
- Beautiful Rockbound Coast of Maine
I saw one advertised on E-Bay from a seller (whose name cannot be spoken) last Monday and I asked where they were made..got a quick answer.. India....asked if they had the same crown as the original...another quick reply..yes exactly the same as the original..Hmmmm OK I can't resist so I order one Monday evening..it arrived yesterday. I imediately set about measuring and comparing, checking specs etc. It measured just perfect, pin height correct, crown shape and height correct, stout firm circlips, ring lands just right....it is a good looking piston...not as smooth a casting inside as a Mahle but I never expected it be. This is great (well, atleast for all the 49sp owners!!) as there has never been an AM piston available for these. This is all good....but now comes the one issue I discovered with these and some may well dissagree with me on this whether it's even a problem or not....but for me, however, it is. When I measured the distance between the wristpin bosses I got .510"....a 49/52 conrod top measures .393" for a running crearance of .117". So I measure a Mahle 49sp piston and get .437" which gives a running clearance of .044" and this is sloppy by most standards I find, as I measure other motors apart at the shop. Here is a sampling 52E .021", 262XP .012", 272XP .010" Now, how tight upper rod end and the piston are dictates how the lower con rod end is held in center on the crankpin and bearing. There is always quite a bit of side play in the lower bearing but the ability of the rod to slide back and forth is limited (or should be) by the upper end fit. This was kind of a bummer to find on an otherwise pretty darn nice AM piston. However this can easily be overcome. What I have decided to do is fit a set of 52E thrust washers to my 49 bearing. This is a bit to fat to fit between the bosses so I will have to mill off around .033" off each boss to achieve a running clearance of .012". Not a biggie...as I have a number of 52/52E thrust washer sets...and after yrs of scrounging used pistons that were not to worn to use, just having one that fits the bore properly is awsome!!!! These could be used in the 52/52E as well but they are single ring as opposed to two.