Pushrod Length: To Spring or Not to Spring

Pushrod Length: To Spring or Not to Spring

Q: When doing a pushrod length check on a GM 350, do I use double valvesprings, or should I take one out? Kenny Matheis Via email

A: Gee, Kenny, I don’t know. It depends how cute the spring is. (Groan.) Theoretical answer: Depending on the quality of the checking pushrods versus the actual pressures of the valvespring pack used in the engine build, there’s a chance you could bend or damage the adjustable pushrods used for determining pushrod length versus valvetrain geometry. So, most cam and valvetrain specialists, including Comp Cams, officially recommend using either light pushrod length checker springs or the inside element of the dual- or triple-spring you’re running. Another plus with “light” springs is that with lower valvetrain loads, the engine won’t try to snap around going up and down the cam flanks as you hand-cycle the crankshaft. That arguably makes the critical rocker arm tip sweep contact-patter across the valve stem top smoother.