From highest power figure to lowest power figure:
- Toda cams and ported big valve head
- ITR cams and Big valve head
- Toda cams and stock head
Car tested :RSX-S with stock bottom end. PRC intake. Comptech headers and
Conclusions from these results:
- With Toda cams the big valve head is worth about 5-10 HP from 6000 rpm up.
- With ITR cams + big valve head the power curve is only marginally better
than Toda cams with a stock head.
- The ported big valve head needs bigger cams than ITR cams to work well.
No comparison can be made between ITR cams and Toda cams in a stock head.
This was not tested here.
Tuning here is essential. Read very essential. The car was tested first with ITR
cams and the big valve head and custom tuned to make the middle run (pink -
purple). Toda cams were then swapped in. The first run with no ECU reprogramming
resulted in virtually no hp change (less than 1 hp). Two hours of tuning
gradually raised the power 6-10 hp. The K series engines are most sensitive to
cam timing. Ignition timing was the next biggest difference followed by fuel
At the upper ends of engine of performance gains are on a diminishing return.
Higher compression pistons might yield a better return than the big valve head
at this point.