How do you calculate valve lash?
To determine the valve lash, subtract the squish from the desired valve opening lift. The cam in the graph is for a flathead, using squish of 0.002″ the valve lash should be 0.0127″ or 0.013″. The exhaust could be set a couple thousandths larger to allow for thermal expansion.
What is the purpose of valve lash?
Valve lash is a small gap between the valvetrain components. It allows the metal parts to expand as they warm up without moving the valves. When the camshaft moves the lifter, it must take up the lash before the valve actually moves.
What’s the best way to set the valve lash?
Shafrioff told us to set the valve lash with a cold engine and check the valve lash weekly with the engine at ambient air temperature. This will give you the best indication of when the lash is changing in one of the cylinders. Ignore the “Chilton Manual” method of setting valve lash.
How often should you change the valve lash?
Scott Shafrioff reminded, “Cylinders heat up at different rates but cold is cold.” Shafrioff told us to set the valve lash with a cold engine and check the valve lash weekly with the engine at ambient air temperature. This will give you the best indication of when the lash is changing in one of the cylinders.
When to set the Lash on the intake valve?
The best sequence to use when setting valve lash is to go by the firing order. This requires less turning of the crankshaft and will help ensure that valve overlap is not an issue. EO/IC rule (Exhaust Opening and Intake Closing). Set the intake valve lash when the exhaust valve is beginning to open.
How does hot valve lash affect engine performance?
Using Valve Lash to “Tune” Engine Performance. For example, by reducing the amount of (hot) valve lash, the valve will open slightly sooner, provide slightly more lift (valve opening), and will close slightly later. This makes the camshaft look bigger to the engine, due to this slight increase of duration and lift.