He has found a North American supplier of Alfin* (ALumnium Ferrous INsert) piston/liner sets. We don't know yet if they're 3-ring or 5-ring, but we'll know that next week. He actually bought the whole kit to rebuild the engine: rod & main brgs, gaskets, etc.
[later edit: 3-ring, but not Alfin -- no insert]
Tiffin Parts LLC
235 Miami St
Tiffin, OH 44883
They seem to be geared to the industrial market (forklifts), so 5-ring is likely. However, there's not a lot of downsides to 5-ring pistons/rings IMO.
Tiffin's website is infected with malware right now (I don't run Windoze, so malware doesn't seem to affect me) so you may want to get there via Google, as Google will warn you if Tiffin's site is still bad:
It's the first link.
Their direct page listing the Nissan engines is here, with links to PDFs with part Nos.:
http://www.tiffinparts.com/products-and ... uides.html
For example, for the SD25 it's
Alfin:TIFFIN PARTS, LLC Phone 1-800-219-6354 Fax 1-888-397-4794 REV 1/23/2012 OTHER PARTS AVAILABLE N12 ENGINE KIT 250 (4 CYL. DIESEL) SD22 NISSAN **********Piston & Ring Size Availability********** STD .50mm 4 PISTONS 12010-J5310 12010-J5310.5 1 RING SET 12033-R8112 12036-R8112 4 LINERS 11012-76200 **********Bearing Size Availability********** STD .25mm .50mm .75mm 1.00mm 1 MAIN BRG SET 12207-37506 12209-37506 12210-37506 12211-37506 12212-37506 1 ROD BRG SET 12117-Y5210 12117-Y5211 12117-Y5212 12117-Y5213 12117-Y5214 1 CAM BRG. SET 13002-71204 4 PIN BUSHINGS 12030-37500 1 0/H GASKET SET 10101-L2526 1 THRUST WASHER 12280-37525 SET 1 FREEZE PLUGS FPK250 [Part No. for all of the above ordered at once: EK250] Valve kit Part No. VK250 4 INTAKE VALVE 13201-Y5200 4 EXHAUST VALVE 13202-Y5200 VK250 Lifter set CK250 8 LIFTERS 13231-78201 CK250 Other parts 1 VALVE SPRING 13203-T7200 1 KEEPER 13208-Z5500 1 HEAD GASKET 11044-V1700 1 IDLE GEAR 13012-L1801 1 F/CVR. GASKET 13520-10H00
From the web:
ALumnium Ferrous INsert PistonIt is a bi-metrallic piston, consisting of a body of aluminum alloy and a wear resistant cast iron inserted for the top grove. The top grove is fitted with a steel chrome in land ring. Which will give a enhanced piston life.
Austenitic means that (amongst other things) it's non-magnetic.ALFIN is inserted within the ring grooves when casting. ALFIN is made of special austenitic cast iron. It is tightly bonded metallically to piston body and counteracts the wear in the top ring groove. ALFIN pistons are commonly used in diesel engines.