motor rebuild

Fri Mar 04, 2005 8:59 am

Thinking about rebuilding my cubs motor this year. Runs good buts smokes like crazy, she'll run through a quart of oil after mowing maybe 20 acres. I saw some cub pistons on ebay, they are .010 over, aluminum and have a hump on them. Mine is a 48 cub. Will these fit mine assuming .010 is enough overbore to get everything round?

Fri Mar 04, 2005 10:08 am

Those forged pistons have been know to cause clearance problems in olded heads. Do a search to see what has been done to fix this. I think you can only get these new( I may be wrong on that) and thay don't make the old cast ones.

Fri Mar 04, 2005 10:08 am

The domed pistons MAY bump into a early cylinder head like yours. You need to check and if there is a problem you can relieve the head for adequate clearance.

Fri Mar 04, 2005 10:12 am

Have you pulled the head yet to make sure it doesn't already have oversize pistons in it? A large number of them have already been rebored at least once. top of piston is normally marked with size if overbored. example .010 or 020.

Fri Mar 04, 2005 5:21 pm

Big John ,the aluminium pistons required a different part# for the rods. You will have to use the cast pistons If you plan on using the rods in the 48 engine.But first you may want to pull our head and do some measuring on the bores to to see if you need to bore or if you are lucky it may just need a set of rings. I too thought I could buy the aluminum pistons and up the HP. but the cost of the rods was prohibitive. After all the machine work .20 over pistons and a rebuilt crank I have over $600. in the engine on the 1949 Steve