4g61t.org

The 4G15 is a very easy motor to work on so I would suggest you build the motor yourself. You will still have to get the machining done by a shop of course but actually putting it all together is very easy.

Performance pistons can be a little hard to source but that's OK since there is an easy option for that. The Hyundai Excel X1 ('86-'89) uses flat-top pistons which brings the CR up to ~10.5:1 and already 'eyebrowed' for a multivalve head (if your going to use the 12v head) and they are readilly available.

The rotating assembly is in desperate need of balancing, as I think little is done at the factory. I noticed a huge difference in my old 4G15 with all the top end harshness disappearing it would rev and make good power all the way to stock rev limit at ~6800rpm.