My current setup is a White Bros E-series muffler with 18 discs, a 165 main, and White Bros filter. Do you think I would benefit from a rev box? Are they worth the $125.00?
Does it just eliminate the rev limiter or does it also change the advance curve? Thank's in advance.

 

White Bros RevBox raises RPMs AT LEAST 1200RPM...and goes as high as +1700RPM.

For stock 400EX, with bolt-ons -- Dont use it.
For 400EX with engine mods -- you will see additional power, BUT the internals of the engine will wear faster.

Can't make up my mind on this issue. My 416EX revs to the limit in each gear very quickly, but I dont want my engine revving +1700RPM.

 

Dont do it. I see dyno charts of the 400 with just pipe and filter and they quit making power 500 or so rpms before stock rev limit. So why rev past that? Only thing its doing is wearing out your valve train and other components faster. If you have a aftermarket cam that is tuned to produce power higher than the stock rev limited allows, then go for the rev kit. But you should also put in heavy duty springs and lighter, stronger valves.

 

IM NOT POSITIVE BUT I HAVE BEEN TOLD THAT THE REV BOX DOES GIVE A FEW DEGREES OF TIMING ADVANCE WHICH WILL MAKE IT REV QUIKER.BUT IM NOT SURE THAT WAS WHAT I WAS TOLD MY EXPERIENCE WITH THE 400EX IT LIKES TO BE SHORT SHIFTED KEEPING IT UNDER A LOAD MAY NOT FEEL AS FAST BUT PUT IT BESIDE SOMETHING REV IT UP THEN RUN IT AGAIN AND SHORT SHIFT IT AND YOULL SEE.