We compared our old pushrods with the Howards rocker arm fixture, indicating they were too short for our new heads, cam, and roller lifter combination. It is critical to have your engine's final dimensions set before measuring. Our new heads are in place with the proper head gaskets installed. Since big-block Chevy heads use different length pushrods between the intake and exhaust, you simply invert the fixture by the arrow indicators.

We then adjust our Howards length-checking pushrods to rest against the inner side of the fixture. This easy-to-use tool slides onto the rocker arm stud and rests on top of the valve stem.

The most simplistic option for small-block and big-block Chevy heads is a molded plastic fixture from Howards Cams that replaces the rocker arm on most Chevrolet applications with factory valvetrain geometry. Too short, and the contact pattern will ride more towards the intake side of the valve. If the pushrod is too long, the rocker will travel across the valve stem too far outward towards the exhaust side of your cylinder head. Getting the exact geometry for the v alvetrain relies heavily on the pushrod length. We can use the wheel to find the maximum lift point with each cam lobe using our cam card. We sealed the bottom end of our block after degreeing our cam and put our degree wheel back in place. We pulled our Howards Cams degree wheel, threaded pushrods, and lightweight valvesprings out of our toolbox. Since our big-block is now equipped with new 24-degree aftermarket aluminum cylinder heads, plus a new cam and roller lifters, this accumulation of parts from different manufacturers will typically demand a new pushrod length. If you view the motion of your rocker arms as the engine rotates, it travels in an arc with the fulcrum as its pivot point. We pulled our Howards Cams selection of tools from our toolbox to get our geometry exact on our current big-block Chevy engine. That engine RPM calculates to all valvetrain pieces cycling up and downward approximately 54 times per second. Let’s say that just before you shift, you’re spinning your engine at 7,000 rpm, a conservative number in many cases. The key is to have these two extremes centered over your valve face. As the rocker travels in an arched motion, it will be slightly outward on the valve face at the maximum lift and inward when the cam is at the base circle. The goal of proper pushrod length is to center the rocker arm over the valve stem.

Chevy 350 with howards rattler cam