Back Cutting Exhaust Valves?

[M E S O G L E A]

Just had my RB25DET cylinder head refurbished at Nagoya Precision in Hachioji. New guides, seats cut, grind valves and a shave, all for only 170000 Yen. I mildly ported the head while it was disassembled.

Anyway, the intake valves have a 30 degree back cut but the exhausts do not. All the research I have done indicates that back cutting improves flow at low lift. My tuner, Fujii Dynamics, says it's not needed because it's a forced induction engine.

I have a set of Tomei PonCams that will be installed.

Any opinions on back cutting?

[The Dan]

all for only 170000 Yen.

You could have shipped the cylinder head over here, had the same job done and shipped back to you for about 50000 yen less.

Back cutting does provide some benefits but your engineer is correct that it has minimal effect on forced inducted applications.