Form follows function. Or is it function follows form? When searching for upwards of 630 hp from a small-block Chevy, it really doesn't matter what follows what-who cares as long is it works? What is it about shaft-mount rocker-arm systems that strikes enthusiasts as being such elusive, exotic pieces? It may have been that way at one point, but with the surreal number of big-power engines roaming the streets, it's just another component to ensure reliable performance.
Jesel's shaft-mount rocker arms, for example, allow for maximum lift and duration from your camshaft. Standard rockers tend not to remain square at the tip of the valve, which can lose duration and lift, which can cost your engine horsepower, and nobody wants that. Also, the Jesel system keeps rocker-arm flex, if any, to a minimum, and its vast array of options (styles, weights, adjusters, and profiles), allows you to custom-tailor shaft mounts for your application.
The biggest advantage of shaft rockers is that they remove the extraordinary friction in a stock valvetrain caused by the short-pivot rocker geometry. A longer-pivot rocker arm reduces the scrub on the valve tip. However, with traditional stud rockers there isn't a way to increase the pivot length.
This month, Mike Consolo from Quarter Mile Performance showed us the dos and don'ts of installing such a system. He says you should step up to a shaft-mount system "when excessive lift is involved or an aggressive camshaft is utilized, including any time you exceed 0.700 lift or when using aggressive cam profiles with durations in the neighborhood of 270 and larger."
If you aren't sure of what you need for your build, don't worry; Jesel's tech line will answer any questions and set you up with the proper system for your application.
Using the supplied checker...
Using the supplied checker from Jesel, we began by measuring the stand height. Ideally, you'll want your stand height to be between 0.025 inch out of the hole and 0.050 inch in the hole. Assuming the cylinder heads aren't warped, the spacing should be consistent across the stand; however, we still recommend checking each individual rocker, just in case you need to space the difference between the intake and exhaust sides.
After taking the initial measurement,...
After taking the initial measurement, we then selected from the wide array of shims included in our kit, which ranged from 0.025 to 0.105 inch. These shims allow you to adjust the stand height and eliminate any high or low spots. It's essential to establish all shim heights prior to final assembly of the cylinder heads.