An R cam on an otherwise stock engine would not be likely to make much more power. It's tuned for fairly high rpms, and to make power at such rpms the breathing needs to have been improved (carbs, head, exhaust) or you will have just sacrificed low end torque and not gained high end power.

A stock 'D' cam ('K' is nearly identical, you probably wouldn't ever notice the difference driving around) perks up a 'C' cammed engine very nicely. There are several aspects involved in the HP gains between the B20B and the B20E, and the cam is at least 1/3rd of the formula (along with bigger intake valves, better intake flow/tuning, higher C/R).

I've also used the IPD 'Street Performance' cam before, which is a slight improvement on the 'D' in a stock engine.

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I'm JohnMc, and I approved this message.