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. flat-tappet cams with Vortec heads.The goal of proper pushrod length is to center the rocker arm over the valve stem. This is the simplest, least expensive route to take when using a single-wound 1.25" valve spring and street hyd. I also ran new GM Vortec seals which work great. The stock Vortec valve guide thickness acts as a dampner of sorts on its own. The one thing you need to do if you go this route is to remove the dampner from the spring. I ran my Vortec 413 like this for over a year and when I took the heads off and stripped them down for a look-see, everything looked fine. The stock Vortec retainers are made of a quality light-weight alloy and the grinding is in an area which does not affect the strength of the part. As stated in the Vortec sticky, all I did was grind about 3/32" off the bottoms of the retainers and I had plenty of R-G clearance.
488"/.510" lift hyd FT cam with single-wound Crane 1.25" springs. For that kind of lift you do not need to do any machine work on the heads.
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