Valve Adjustment
There is more than one way to properly adjust valves. Different people set
valves in different ways. The two methods list here are what I use on a
regular basis (depending on whether I'm running all the valves or just one or two).
Both methods are to be used with the engine not running.
Method #1:
For a small block Chevy (or any engine with a firing order of 18436572)
you can set the valves by turning the engine over just two times. Bring the
engine up to #1 firing (both #1 valves closed and the timing mark aligned
with zero on the timing tab) and adjust as follows:
exhaust valves 1,3,4,8 and
intake valves 1,2,5,7
bring engine up to #6 firing(rotate engine one complete revolution) and
adjust as follows:
exhaust valves 2,5,6,7 and
intake valves 3,4,6,8.
Method #2:
This is the one I use and it goes like this: when the intake valve on a
cylinder has opened fully and is almost closed, adjust the exhaust valve
of that same cylinder. When the exhaust valve starts to open, adjust
the intake valve of that same cylinder. This method takes a little longer
but it works very well.
Adjustment Procedure:
The above two methods are just for getting the cam rotated properly
so that the lifters are on the base circle for valves you are wanting to
adjust. The actual adjustment for hydraulic cams goes like this:
While spinning the pushrods with the thumb and index finger, tighten the
rocker arm until the you feel slight resistance to turning the pushrod. This
is zero lash. Then go an extra 1/4 turn (that's my preference). Some people
recommend going with as much as 1 full turn past zero lash, but I've had
the best results with 1/4 to 1/2 turn.
If you are starting from scratch and none of the valves are adjusted, you
won't be able to watch the valves and get an accurate picture of
what's going on. You'll have to watch either the lifters (if the intake isn't
installed) or the pushrods.
If you get the valves too tight, the motor will idle very roughly (if it idles
at all). If this happens, back off on the rocker nuts a 1/4 turn at a time
until it idles well and all the rockers are quiet.
If you set the valves too loose, the rockers will tick (due to the clearance
between the rockers and the valve).
Take note that most cheaper rockers with roller tips will click no matter
how many times you adjust them.
For solid-lifter cams, the method for getting the lifters on the base circle
of the cam (also called the heel of the lobe) is the same; the adjustment
portion is the only difference. Instead of finding zero lash, you adjust the
rockers until you have about .018" gap between the tip of the rockers and
the top of the valves. This is done with feeler gauges. Tighten the rockers
down until you feel a very slight drag on the feeler gauge as you move it
between the rocker and the valves. .018" is a common lash setting, but
always go with what you cam manufacturer recommends for you particular
grind. Solid lifter cams will tick no matter what, so don't be concerned with it.
If you have any questions or comments please click the "Contact Craig" link and let him know.
Copyright © 2009 Bruce Johnson and Craig Watson
