@Sivan :
Yes, that's i think lot more better to work on individual parts ot have lot more speed.
Does the terrain neightbours adjust their height smoothly with the chunck you modify ?
You should have chunckc with more resolution perhaps ? we see a lot the polygons, just y taste and perhaps your game won't need that ?

@Realspawn :
Their was a simple racing game without physic contribution.
(But i don't remember where it was).
Good work, looks pro.