sleepless SOHC

first wanna say hi to everybody, just new here. here's my dilemma i know this has been done and asked so many times. i have a 89 g with a sohc and i wanna swap the head to dohc, since i'm due for a gasket replacement. the swap will be more convenient for me and a local shop won't dare to do a whole motor swap. i've seen some posts which are very helpful but it's a 64 to 63. what's bugging me are: do i have to change my ecu, harness, intake manifold, and on the books there's 2 belt tensioners for the dohc, how do i add that. this has been bugging me since i got my g here in LA back in '02. fell in love with the gti many years back in manila, help. thank you!

'89 galant
'99 g esv6

Wow, that would be a big undertaking. You would have to swap the wiring harness for sure just to have a usable ignition. In addition, you would have to change to pistons out to the DOHC ones, the oil pump needs changed (becuase the SOHC oil pump pulley wont match the DOHC belt).........all the mountings and such are there, you just have to pull everything from the DOHC ..........Ive done it to a SOHC 4G64 with success.

For the 4g64 swap you dont have to change pistons or the oil pump or anything, but I have no clue about swapping a SOHC 4g63 to a DOHC. I wouldnt think you would need to change pistons though.

Trust me, you need to change the pistons. The stock ones have a high rise top with huge cutouts for the the valve reliefs. If you would attempt the use the stock ones (and I did try this) your CR will be over 13:1. On a brighter note tho, the pistons for the dual cam are plentiful whether aftermarket or stock. If you are really serious about it, I can tell you exactly what you need to do, Ive done 3 of them.