Many gearheads buy their cylinder heads fully assembled and don’t have to sweat making sure all of the various parts are set up correctly. But for those that build their own, or that just need to swap to different springs, then it’s critical that they nail the proper installed spring height.
The installed height of a valvespring is the distance from the base of the spring to the bottom of the retainer when the valve is closed. If the distance is too short the spring will be under too much tension, and if the distance is too great the spring will want to “dance” around. Each camshaft you buy will include a cam card that lists a recommended installed height. Following that recommendation will make sure you don’t end up with a spring that is too weak (valve float) or too strong (too much spring pressure that can wipe your cam).
It’s really not rocket science, and you only need the most basics of tools to do the job right. An accurate measuring device like a small mechanic’s ruler or a set of calipers, a valvespring compression tool, and a few hand tools are all that’s required. You’ll also need a selection of shims so that you can adjust the height, if needed. It may seem unnecessary, but this is one of the many critical steps necessary to make sure your engine makes power and stays trouble-free.
01. Using a spring compressor, we removed the old springs, retainer, and locks. A small magnet made grabbing the locks easier. If your new springs didn’t come packaged with retainers you’ll need to make sure the retainers you’re using fit the new valvesprings. The fit can be snug, but if it’s too tight it can overstress the top of the spring, causing failure. If the fit is too loose, the spring can dance around and cause premature wear.
02. We then carefully removed the valve seals. They make special tools for this that help ensure the seals don’t get damaged, but if you’re careful you can use pliers. Before doing this you might want to check your retainer-to-seal clearance. To do this, measure the distance from the bottom of the valvespring retainer to the top of the valve seal. Then add 0.090 inch to the measurement. The number should still be larger than the maximum valve lift of your camshaft. If not, you’ll need to machine your valveguide to get the needed clearance. After all, you don’t want the retainer crashing into the seal when the valve is fully opened.
03. We then slid the seals off of the valve stems.
04. With the spring locator in place, we installed the retainer (with locks) and measured the distance from the bottom of the retainer to the top of the locator. We then checked this number against what was recommended on the cam card. An installed height of +/- 0.020 inches is acceptable.
05. Different style springs require different locators. More common are the type that index on the center of the springs but there are also “cup” types that index on the outer edge of the springs. Make sure you use the correct type for your springs.
06. If the installed height is outside of the allowed 0.020-inch variance, then action will need to be taken. If the distance is too little, machining of the valvespring seat will be necessary. If the distance is too great, then valvespring shims will need to be added. Shims come in various thicknesses and can be stacked if needed.
07. The shims were then stacked in the spring pocket.
08. The locator was then placed on top of the shims. At this point it’s usually a good idea to reinstall the retainer (with locks) and re-measure the distance before putting the valve seal back on.
09. The new distance came out good, so we went ahead and reinstalled the valve seals.
10. We could then install our new Comp valvesprings using our installation tool.
11. This process was repeated seven more times, and we were done with our cylinder head.