want to do a 400 kit, piston,cam, porting. was told the bottom end won't hold to gether, any truth to this

 

I just finished my 440exwarrior tonight. It cost me less than a complete rebuild and smoked my friends 370 warrior with a cam. It also beat a piped z400 and a piped predator. Total build cost was under 3000, and that included custom paint. Pics will be up soon.