Walk me through new Valve Springs, and Rocker Adjustment


Founding Member
Mar 7, 2002
Cape Cod, MA
I think i get the idea on how do do this but, the manual isnt to clean on some things. Ihave Gt-40 p heads. I am installing a set of trick flow springs, a cam, and some 1.7 roller rockers. How do you go about checking/shimming the rockers.I need to know how you do each one. My cam came with some shims, but how do i measure what i need? also tips on installing the valve springs would be great thanks! i just need to know where to have the pistons when adding air to teh cylnders.
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Ed's instructions are for adjustable rockers. There are some unnecessary steps and some unincluded steps for non-adjustable rockers.

You can change the valve springs while the heads are on the car, but it's 100 times easier to do when the heads are off the car. If you pull the heads, you need a valve spring compresser, which looks like a giant C-clamp. Compress the valve spring, and pull the retainer off. It's very simple and self explanatory when you look at it. It's just a bit time comsuming.

When you use pedestal mount rockers, set the fulcrum down, mount the rocker, and tighten the bolt down with the rocker centered on the valve tip. After you've done that, get a dial indicator out and find exactly where 1/2 lift is. At this point, the pushrod and rocker arm (cup) should create a 90* angle. If the angle is less than 90* at 1/2 lift, you need to get a shorter pushrod or go to a smaller shim. If the angle is greater than 90* you need to get a longer pushrod or go to a bigger shim. I've never used shims before, but I assume that you put them under the fulcrum.