Pictures  of SD 508 innards
Hello, while tossing metal junk into the gutted van,I came across these. The sd 508 is similar to the sd709. The709 has 7 pistons crammed into the same sized circle.7 cylinders give  smoother operation. The stroke is very short and the pistons are big,here onm  the 508.The crankshaft looks like a slice of cheese.It rotates and pushes on the rear piston plate.Takes 3 to 5 hp to run this thing.Liquid refergerant will "slug the compressor and destroy teh reeed valves. The difference between a rebuilt compressor and  new,is that the rebuilt is as follows:The new clutch,pulley is used.a new reed valve set,new shaft seal  new oil,new paint.thats it. All these pistons and many bearings are not touched.   http://stores.ebay.com/WerksforWagons
http://pg.photos.yahoo.com/ph/rogersisler2000/album?.dir=/9da2re2&.src=ph&.tok=phbtRrFB69HiSDVS