According to one aspect, a rotary exhaust valve system includes an arcuate ring having a first plurality of apertures and a rotary valve ring disposed in an overlapping relation with the arcuate ring. The rotary valve ring has a second plurality of apertures forming therein corresponding to at least some of the first plurality of apertures. A first crank is disposed in a first side of the rotary exhaust valve system, and a second crank is disposed in a second side of the rotary exhaust valve system. The second crank is connected to the first crank and the rotary valve ring, and the first crank actuates the second crank and moves the rotary valve ring such that openings of the first plurality of apertures are closed and opened.

According to one aspect, a rotary exhaust valve system includes an arcuate ring having a first plurality of apertures and a rotary valve ring disposed in an overlapping relation with the arcuate ring. The rotary valve ring has a second plurality of apertures forming therein corresponding to at least some of the first plurality of apertures. A first crank is disposed in a first side of the rotary exhaust valve system, and a second crank is disposed in a second side of the rotary exhaust valve system. The second crank is connected to the first crank and the rotary valve ring, and the first crank actuates the second crank and moves the rotary valve ring such that openings of the first plurality of apertures are closed and opened.

A gate valve is comprised of a gate movable between open and closed positions within a valve body, and gate having defined through it the gate an equalizer port or passageway between opposite sides of the gate with fixed side walls. The equalizer passageway being is opened and closed by an internal gate. The internal gate is in a close fitting engagement with each of a pair of opposing valve seats mounted with the gate and is shiftable by a carrier that does not constrain movement of the internal gate as it sits between the valve seats.