Each engine, by design has an RPM spread where it develops it's maximum torque/Hp. RV grinds optimize the torque potential at a lower rpm. This allows you to get a heavier mass into motion with less engine revs.
I just added a modified RV grind to my 235 which improved my low end torque at a lower engine rpm.
Couple up this extra grunt with the proper gearing and you can improve on fuel economy by making your power with less engine rpms. My engine develops 25 inches of manifold pressure at idle and will pull along at 70 mph@2000 rpm's with a .72 T5 tranny and I expect 20 mpg after she's broken in.
If you're planning on building up a hot rod with pure performance in mind, you might want to anticipate finding a more radical grind. Hope this helps.
Dave
