I just went through this procedure during original build and then again in the car after recently advancing the cam. It's pretty simple if you have the right tools. Here is the valve spring tool (SUM-906784) from Summit needed to swap valve springs - image below was from original bench build but you can do this with the heads installed - make sure the piston is at TDC so as to not run the chance of dropping the valve into the cylinder during the spring swap.
![Image](http://i263.photobucket.com/albums/ii137/arkwoo/IMG_0124.jpg)
You'll also want to get a set of light checking springs. You could maybe do this without swapping springs but it'd be a bitch to do, especially if you're running really stout springs in your race motor. Here's a set of Comp springs (CCA-4758-2) from Summit (there are others avail as well). You'll want to be sure to get a set of springs which will fit over your installed valve seals. Note the use of these in the images below. You'll also need a dial indicator with either a clamp-on or magnetic base. You'll note in the pix below I fabbed up a light piece of strap which I bolt down using the valve cover bolt holes - this serves as a handly platform for this sort of activity. In the two pix below you can see me checking valve to piston clearence both on the stand and in the car. I am using a degree wheel here but you can do the same thing using your installed damper, assuming it's degree marked appropriately.
Dial indicator w/trainer springs - on engine stand
![Image](http://i263.photobucket.com/albums/ii137/arkwoo/IMG_0182.jpg)
Dial indicator w/trainer springs - motor in car
![Image](http://i263.photobucket.com/albums/ii137/arkwoo/IMG_0331.jpg)
Checking Piston to Valve Clearance
It is recommend at least .080" clearance for intake valves and at least .100" for exhaust valves.
Add .030" to these figures if you have aluminum rods.
The easiest way of checking piston to valve clearance in an engine with the cylinder heads installed is to use a pair of light checking springs in place of the normal valve springs on #1 cylinder. These light springs will allow you to depress (open) the valve easily at any time during engine rotation to measure the piston to valve clearance.
After the checking springs are in place on #1 cylinder install the rocker arms and adjust valve lash to zero on that cylinder. As a general rule, the closest point of piston to valve clearance during the rotation of an engine is between 15 degrees and 5 degrees before top dead center overlap for the exhaust valve and between 5 degrees and 15 degrees after top dead center overlap for the intake valve. This sequence takes place during the overlap cycle when both valves are open, 360 degrees from the top dead center compression stroke.
Note: The actual position of closest piston to valve clearance will depend on how far advanced or retarded your cam is. Remember, as you advance your cam you will lose intake piston to valve clearance and as you retard your cam you will lose exhaust piston to valve clearance.
Exhaust Valves: With the exhaust valve on #1 cylinder adjusted to zero lash turn the engine in its normal direction of rotation until you come to 15 degrees before TDC on the overlap stroke. Set the tip of the dial indicator on the exhaust valve spring retainer, in line with the movement of the valve. Preload and zero the dial indicator to about the mid-point of travel. Depress the valve with your finger by pressing on the valve end of the rocker arm until the exhaust valve contacts the piston, making note of the reading on the dial indicator. Repeat this procedure every 2 degrees until you reach 5 degrees after TDC. Remember that the piston and valve will both be moving relative to each other – either reset the dial indicator to zero before each clearance check or subtract the difference in relative positions.
Intake Valves: With the intake valve on #1 cylinder adjusted to zero lash turn the engine in its normal direction of rotation until you come to 5 degrees before TDC on the overlap stroke. Set the tip of the dial indicator on the intake valve spring retainer, in line with the movement of the valve. Preload and zero the dial indicator to about the mid-point of travel. Depress the valve with your finger by pressing on the valve end of the rocker arm until the intake valve contacts the piston making note of the reading on the dial indicator. Repeat this procedure every 2 degrees until you reach 15 degrees after TDC. Remember that the piston and valve will both be moving relative to each other – either reset the dial indicator to zero before each clearance check or subtract the difference in relative positions.
Notes:
Hydraulic lifters - do NOT preload the lifter when setting 'zero lash'. When setting zero lash, tighten the rocker until you get a light drag while spinning the push rod.
Fly cutting - if you do not have adequate piston to valve clearance you can flycut the pistons in place (in the block) by buying a valve relief flycutter and an old head. You can find any number of articles on the net describing this. Not something I'd want to try in the motor, but people do it.