Adjustable Valve Lash – Roller Rockers
How to dial in pre-load on hydraulic lifters with the Yella Terra adjustable Street Terra roller rockers.
One of the advantages of the Yella Terra roller rockers is the adjuster placed on the tail of the rocker arm where the push rod seats. As you turn the adjuster it moves up or down when you tighten and loosen it. This places preload on the lifter to take up the valve lash.
With the engine not running, turn the engine over by hand using a socket wrench until the rocker arm’s corresponding cam follower is in the base circle of the cam shaft. Make sure the lock nut is loose enough for you to adjust the adjuster. You need to tighten the adjuster down until the valve lash is taken up. The valve lash is the distance between the top of the valve and the roller tip. The easiest way to know when you have taken it up is to twist and rattle the push rod as you tighten the adjuster down.
You will feel the push rod get clamped at the moment you have taken up the valve lash fully. You can back it off and nip it up again to be sure you are spot on. Once at this zero valve lash you can now place some pre-load on the lifter so that the lifter’s internals is not hitting its upper end limit and the push rod is nicely cushioned by the lifter during operation.
Typically the recommended lifter pre-load is ½ to ¾ of a turn of the adjuster. Personally I do not like too much lifter pre-load and I tend to work on ¼ to ½ turn. It is important to realise too much lifter preload will hold the valves of the seats and can lead to burnt valves and not to mention the poor power because of loss of compression, so do not put more on it than you need.
Once you have it set then hold the adjuster in position with the Allen key while you tighten the lock nut up. Now do the same for all the others and you are done. |
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