How come know ever does a DOHC swap on a SOHC motor? I heard the block was the same, so i don't why any doesn't do it is there something i'm missing or if anybody has doen it what was involved?
The reason is because of the cost and hassle of getting all needed parts together to perform the swap. It is POSSIBLE... just easier to buy the whole 4V engine.
You would need new heads, timing covers, exhaust manifolds, intake manifolds, throttle body, ECU, injectors, and more.
In addition, you still wouldn't have the 4V forged crank and your compression would go way down dropping your power.
If you want a 4v- just buy a used one out of a wrecked cobra or as a crate engine.
the average person just does not have the time or the ability to do the proper swap. plus the 4v motors have better water and oil pumps. the 4v oil pumps are a little larger, have a larger pick up tube and flow a little more because you need more oil in the 4v heads than the 2v heads. if you pulled your motor and stripped it down to bare block then built it up with the right parts that would be ok. that said its a lot easier to just buy a 4v crate and swap the motors and computer. its the same thinking that dealers use with transmissions, instead of rebuilding a blown 4r70w, they just put in a rebuilt one. i used to work at a L/M/Mazda dealer and thats what i did all day. i actually priced it out with all the parts to see what would be cheaper and all the parts alone cost more than a rebuilt trans. same goes for motors