The red top is the earlier version of the SR20DET motor... it has timing chain problems which could make it slip off and kaboom the motor. That's why I put a black top (newer version) in my friends car. Justin(OKC) will love this... he built a 510 from ground up...literally took every bolt off the car and redid everything....built motor w/ high compression, cyramic coated crank, pistons, etc. He sold it to his buddy that helped him build it years ago... he told me he's gonna try to buy it back and was thinking of installing an SR20DET into it. Should be interesting.