FAQ Regarding Cobra Drivetrain Setups

[blykins]

I get asked a lot about the best method of setting valve lash/preload.

The jist of it is you want to set the lash when you're on the heel of the cam lobe. On a cam with a lot of duration/overlap, you stand more of a chance of catching a valve still slightly open if you use the other methods (such as setting the valves with the piston at TDC of the compression stroke and then going every 90°, following the firing order).

With the EVO/IVC method, you're basically insuring that the lifter is on the lobe heel.

For instance, if you're setting the intake valve lash, bump it over until the exhaust valve is starting to open. You know that the intake valve is going to be totally shut because you're on the exhaust stroke and the exhaust valve is starting to open. You would have to go through the motion of fully opening the exhaust valve and starting to shut the exhaust valve before the intake valve would start to open again.

Conversely, on the exhaust valve lash, you bump it over until the intake valve on that cylinder is starting to close. You know that the exhaust valve is going to be fully shut because the intake valve is closing and you're getting ready to light a fire in the thing.

When I have an engine on the stand, getting ready to go on the pump or in the car, I run the valves this way, on both a solid and hydraulic cam. For cold aluminum headed iron block engines, I aim about .006" low on the lash and then let her have it.