One of my last motor projects for this winter is the installation of a new performance camshaft kit, which includes the camshaft, lifters, valve springs, valve retainers, spring seats (or cups,) and locks (AKA keepers.) This article details the proper way to install valve springs on a head and shows some special tools in use. If you are not familiar with these tools, some additional information about them plus some helpful tips can be found in the companion tech article “Installing Valve Springs-The Tools”: http://www.fordmuscleforums.comtec...ngs-tools.html
The camshaft manufacturer or provider will specify the exact components that should be used in a camshaft kit. It is not recommended for the amateur builder to vary from using these parts or the tolerances provided. Warranties may also be voided if you stray from their exact recommendations.
Although the pictures shown in this article are of a head that is lying on the work bench, the procedures shown can also be performed on the vehicle using the same techniques and tools illustrated here.
Here are the parts that will be replaced on an AFR 205 cylinder head:
First I removed the old valve springs using this compressor and a magnetic retriever:
Once the locks were removed I removed the valve spring compressor and set it aside. Next I removed the old spring retainer and the spring. Before the spring seat could be removed, I had to remove the old valve stem seal. The easiest way that I have found to remove this type of seal is to gently rock them back and forth with a pair of pliers while giving it a light and steady pull:
I then removed the spring seat and the spacer shims that I found under it. I also checked to see if there was any spacer shims found under it in the pocket. I knew I hit bottom when I found nice shiny aluminum:
The next step is to determine the base spring height that my head and the new valve train parts were capable of. Spring height is a measurement between the top of the spring seat (or cup) and the underside of the spring retainer when the valve is fully closed. Once I know the base, I will be able to compare that value to the recommended height found on my cam card.
There are 2 good ways to measure the spring height. The first way uses a valve spring height micrometer and the second uses a telescopic gauge. I will show how to do the measurement both ways.
To determine base, I needed to use the new spring cup, retainer, and locks. I first made sure that the spring pocket was clean and free of burrs. Then I installed the spring seat without using any of the spacers underneath:
Then I fully collapsed the valve spring height micrometer and put it on top of the spring cup. Collapsing is just a simple twist of the top while holding its base in place:
Next I install the spring retainer and then the valve locks:
To get a measurement, I rotated the micrometer around so that I could see the horizontal graduations then, while holding the base of the micrometer, I spun the top of it until it firmly rested against the retainer:
Study the photo above and you should see that it reads 1.922.” Because this particular micrometer has a range of between 1.600-2.100”, the 1” in the calculation is understood as a given.
I recorded the reading next to the valve with a permanent marker.
I then removed all the parts and repeated the procedure on the next valve. I worked until I had measured all the valves, being sure to record each value for reference in a following step.
As suggested above, I could have also done the measuring with a telescoping gauge. To do it that way, I used a valve checking spring between the seat and the retainer and secured it with the locks.
Then I place the telescoping gauge between the seat and the retainer. I held it upright and squarely between the parts and then lock the gauge length:
The actual measurement is determined using a dial or digital caliper:
With careful practice, I was able to get readings that were within .0015” or less of the valve spring micrometer method. This small variance is considered an acceptable.
After I had calculated the base for each valve, I compared the readings to the installed height specified on the cam card. For this example, the cam card specified that my springs should be at an installed height of 1.900-1.920”. Unfortunately my base reading of all 16 valves ranged from 1.922” to 1.944”. To correct this situation, I needed to add shims under the valve seats. The shims will move the seat higher and a little closer to the retainer.
The hardened valve shims that I have are .015" and .030" thick:
Once I determined what shims were to be installed, I re-measured the spring height to verify that the valve was now within the 1.900-1.920” range.
In this case, using the shims easily solved my problem. Had I needed to increase spring height, I would have used a +.050” valve lock or a special type of retainer that would give additional clearance. Here is a pair of regular (black) locks and a pair of the +.050” locks (gold):
Examine the difference that the locks make in the following 2 photos:
The top photo shows the retainer to valve clearance using the standard locks, and the bottom photo shows the same with the +.050” locks installed.
There are other more drastic ways to increase the installed height. Installing longer length valves or having the valve seats sunk further into the head will both give additional clearance. Sinking the valves further into the head should be avoided whenever possible.
The final procedure needed was to measure the valve retainer to valve stem seal clearance. The retainer should never make contact with the top of the seal while the motor is running, as that would be a very bad situation.
I put the shim and seat that gave the desired spring height as found above and then I installed a new Viton valve stem seal using a driver:
Next I assembled a single cylinder’s intake and exhaust valve with the valve checking springs. I then install the desired retainers and locks. Because I will need to push the valves open in the following procedure, I suspended the head between two 4x4’s.
I set up my dial indicator on one of the valves. With the valve remaining fully closed, the indicator’s shaft was compressed most of the way when rested on the valve. This allows for a full range of motion when the valve assembly is pushed downward. I adjusted the dial so that it read zero before pushing the valve open.
Then I gently pushed the valve and retainer against the top of the valve stem seal:
The difference between the 2 readings should be less than the total valve lift found on the cam card, plus an additional .060” or more. Since I found that I could move the valve a total of .964 before it reached the top of the seal, in this respect I could have safely ran a cam with up to .904” of lift (.964 -.904 = the .060” minimum clearance needed.) If the clearance is less than what was safe, then I would have needed to try a different type of valve stem seal or a different type of retainer (which would require setting up the spring height again.
Since this measurement was satisfactory, I did a final assembly of that valve with the new springs that were recommended for the cam.
Because I had way more clearance than I have total valve lift, there was no reason to check the remaining valves. I did fully assembled the heads being careful to use the parts that maintained the desire spring height.
With the procedures shown above, the reader should gain a reasonable understanding of how to properly setup a fresh set of springs on a cylinder head and how to use some basic measuring tools in order to accomplish it. If nothing else, you should gain an appreciation for the work a good machine shop will do when setting up performance heads. It should be noted that there are other checks that will need completed once the new camshaft, lifters, and rocker arms are installed on the motor. In a future tech articles I hope to cover some of these topics, such as rocker arm to retainer clearance and coil bind, plus piston-to-valve clearance, and how to determine pushrod length—all of which are very important for engine longevity.