What engines will work in my CC 1604 and where to look
 

The valve seat in my 16hp twin B+S engine is loose and came out. Block seems too wallowed out to even begin to repair. I started looking for a replacement engines to get some ideas on prices and I can't seem to find much out there. I have a Cub Cadet 1604. My question is will any other engines fit inside this tractor with minimal modification or am I stuck having to find an exact replacement? Also is there a special hideout on the internet somewhere for mower parts? Im looking but not having much luck.

Easy way is to find the same engine that it has but you can put something else in it but that will require getting all the parts to adapt to your drive line. I’d be looking on C-List or Flea Bay for one like you have.