Re: 1991 90HP Force problem updated motor is shot & rebuild started
Wiseco piston rings have a 2 degree taper on the top so top really is top or up toward the piston crown. If you have strong thumbnails, spread the ring gap with them and slide the rings over the piston. Not too easy but it works for me.
As for the piston, snap rings need to go in with the gap either up or down, to avoid the rings flexing and possibly loosening as the piston stops at TDC and BDC. Take one snap ring and put it in the wrist pin hole at 90 degrees. Push it in then tilt it into the groove with a screwdriver. After installing the rod and wrist pin, set one end of the other snap ring into the groove in proper orientation. While holding down with your thumb, use a small screwdriver in the notch and roll the ring into the hole. Then push down to seat in the groove. Not too easy until you get the knack of it, but do-able.
It is not too critical which side of the rod faces up, however there is a flat groove and a notched groove I suppose one is to drain excess oil from the bearings. However, the flat groove (drain) faces down with the piston in proper position in the bore.
Plain grease will hold the rollers and wrist pin needles. After installing in the engine, flood them with TCW-3.
Remember to properly align the rod big end caps BEFORE tightening more than hand tight. There are two polished flats on the side of the rod and a pencil point, small screwdriver, or dental pick must move over the crack smoothly without catching. You did mark the caps and rods, didn't you? The caps only go on one specific rod, and in one direction because the cracks on either side are different. After alignment, tighten the cap bolts to 190 inch pounds in two stages. You can use threadlock compound for extra security, some of the original engines had it on the threads, but I have not yet found it necessary.
