Is it possible to make a subaru ej253 sohc motor into the ej255 wrx or ej257 sti motor?

Answer 1

There is a company in Australia that has designed a supercharger for the 2.5 Rs (ej253). It makes the Rs equal to the wrx. But that's really all youll get out of the ej253. It doesn't handle more that 6psi well and the block doesn't have the same cooling as an wrx/sti block. To rebuild it with all the parts would be a waste when you can find an wrx/sti engine block for the price you would pay building up an ej253.