Reply to "Pushrod diameter - 393cui"

I know drag racers who swear by the Manley 3/8" push rods. I've always used custom ordered 5/16" push rods.

The outside diameter of a push rod is not the only consideration. The wall thickness of the tubing it is manufactured from is also important. A 5/16" OD push rod manufactured from tubing having 0.120" wall thickness will be very stiff. The hole in the middle of such a push rod is only 0.072" diameter ... its almost a solid push rod. It also serves as a nice way to meter the flow of oil to the valve gear. Finally, the material the tubing is manufactured from is also a consideration. A cromoly alloy that is light yet stiff is a good choice. The guys who manufacture custom push rods for race teams are normally well versed in the pros and cons of various materials, and can offer a recommendation.

I think my next set of push rods will be tapered, which is the hot tip today. Custom made tapered push rods are sold by at least two companies I'm aware of, Manton and Trend. Like beehive springs, tapered push rods cancel resonance by virtue of their shape. The rods will be 3/8" at one end, tapering to 5/16" at the other end. I'd like to still use 0.120" tubing if possible.

Choice quality stuff.

-G