How To Install Valve Springs
Racing Valve springs are one of the most critical and most often overlooked components in your racing engine. Making the appropriate selection of valve springs for your racing engine begins with accurately identifying the application and selecting all of the valve train components to achieve your goals for the racing engine you are building.
The valve spring that is ultimately selected must be carefully matched other components in the valve train in order for the engine to reach its full potential. It is foolish to install a cam that will rpm to 8000 if you do not have the correct racing valve springs that will withstand that rpm range. The incorrect selection of the racing valve springs is one of the leading causes of engine failure. In addition, many racers suffer failure due to the incorrect installation and improper handling of the valve springs.
How to Select a Racing Valve Spring:
- Use only racing valve springs that provide the correct spring pressure with the valve both on the seat at maximum lift.
- If the outside diameter of racing valve spring requires it the spring pocket of the head will need to be machined to a bigger size.
- To avoid a very common and costly failure, special care must be taken in positively locating the valve spring. When a valve spring moves around on the head or retainer it causes harmonics and subsequent excessive wear. A valve spring that is forcebly installed onto a retainer is very likely to fail at that coil. Careful selection of the matching steel or titanium retainers, spring seat cups and spring locators is the key to a successful and reliable installation. Valve springs that are installed properly at the retainer and cylinder head will provide the longest service life and reliability from failure.
Proper Spring Handling of Racing Valve Springs:
- Always be sure to handle racing valve springs with care. Never grab them with pliers, strike with a hammer or clamp them into a vise. Doing this damages the surface of the spring, which will subsequently lead to a spring failure.
- Always use a plastic tool or object when separating double or triple valve springs that can't harm the surface of the valve spring. Don't ever use a hard metal tool like a screwdriver when working with valve springs.
- Racing valve springs are typically shipped with a rust preventative coating that should not be removed during the engine build. Valve springs should not be cleaned with evaporative or acidic cleaners. This can cause rust on the surface of the valve spring which can lead to complete failures. Corrosion in any amount is a major enemy to racing valve springs.
- Always use a high quality assembly lubricant designed for valve train components when installing racing valve springs to make installation easier and also improve valve spring life.
How to Check Valve Spring Loads:
- Top quality racing valve springs are typically sold in "matched sets" with a variance of + or -10% for valve spring load consistency.
- Use a high quality valve spring load tester when checking the spring loads and measure the thickness of the retainer where the outer spring sits. Be sure to assemble the retainer on the spring and place on the base of the spring checker when checking valve spring load.
- Then proceed by compressing the valve spring to the desired installed height. The installed valve spring height is calculated by measuring between the top of the valve spring where the outer spring sits in the retainer, and the bottom of the valve spring on the base.
- Be sure that the thickness of the retainer is not included in your installed height calculation since it is accounted for when compressing the valve spring.
Installing Racing Valve Springs
- Before installing valve springs on the cylinder head, double check the installed spring height. First, install the valve in the guide and then you proceed with installing the retainer and valve locks. Then pull the retainer tightly against the valve locks while holding the valve assembly steady while measuring the distance between the spring seat and the outside step of the retainer using a height micrometer, or snap gauge and a pair of calipers. Repeat this proceedure for all the valves, and locate the shortest height which becomes valve spring installed height for your particular cylinder heads. Be sure to allow for the inner steps of the valve spring if you are using dual or triple valve springs.
- Use valve spring shims to set the installed height within ±.020” on the rest of the valves.
- Be sure that you measure the distance between the top of the valve seal and the bottom of the retainer before removing the retainers to ensure is greater than the lift of the valve. If the distance is not greater the guide will need to be machined to prevent camshaft failure.
- Be sure to carefully check for coil bind after the valve springs are installed. You must have a minimum of .060” clearance between the coils of the inner and outer valve springs or you will need to change the retainer or valve to create more installed height, or possibly use an alternate valve spring that is suitable for the camshaft lift. You can also machine the spring seat for extra depth.
- Since rocker arms are designed to clear specific spring diameters, you must be sure that you have made the appropriate selection of rocker arms and retainers to ensure proper clearance. Rocker arm clearance issues can be a result of improper rocker geometry, and many times can easily be corrected different length pushrods or valves.
- Be sure to spray the valve springs, rocker arms and pushrods with a high quality valve train lubricant to assist in the proper lubrication during initial start up and break-in of your engine.
How to Break-In a Racing Valve Spring
- New racing valve springs need to take an initial heat-set to ensure against permature failure. During the first start-up be sure to limit the engines rpm to between 1500 and 2000. Once the engine temperature has reached operating levels you can then shut off the engine. Never rev the engine to high rpm when the springs are newly installed. Allow the valve springs to cool to room temperature and this will typically prolong spring life and eliminate premature spring failure. Once the valve springs have been broken-in, it is not at all uncommon for them to lose a small amount of pressure. After that the valve spring pressure should remain consistent unless the engine is overrevved or abused causing the valve spring to be overstressed. If this occurs, after careful inspection for damage the valve springs must be shimmed to the correct pressure or replaced.