Quote:
I know if you put a 4G63 head on a regular 4g64 block with the original pistons, it gives you an insanely high compression ratio, like 11 or 12:1
Not true for the 4G64 SOHC 16v head and 4G63 16v turbo DOHC head, they have the exact same cc's. Just plug the holes in the 4G64 block not needed, use correct head gasket, run the correct cam gears/belt combo and figure out what your going to do with the distributor (swap to cas).
I'm not sure on the 8v heads as I didn't do any research on them when building my motor in various stages.
Manley makes 4G64 pistons, I used them to drop my ratio to 8:5.1 from factory for my application.
I've been down the road your going with the factory 4G64 and turboing it reliably. If all you want is a little boost and moderate power, you can get by with 6-8 psi on factory rods/pistons if your motor is in good shape and you have supporting mods. Keep in mind for the 4G64 turbo you still going to have to buy all the turbo parts to make it a turbo powered motor ( turbo parts, fuel pump, injectors, ic piping, intercooler, etc., etc.).
If you want to do more, it will be easier to drop a 4G63T ecu swap and rewire. I started out forged 4G64 turbo on SOHC 16v head, WBO2, safc (8psi). Then swapped to 4G63 turbo head, custom distributor so I could run on the factory ecu/safc (12 psi safely). I did actually run 16 psi for a little bit, but timing was out of whack and blew a head gasket eventually. Now I have done a harness swap, eprom ecu swap, ecmlink.
If I had to do it all over again, I would have went straight to a 4G63T engine/ecu swap and been done with it. There is a reason the majority of people who turbo these vans do the 4G63T swap.