[Healeys] Adjusting Valve Rocker Clearance

[Bob Spidell]

AKA 'The Rule of 13' for a 6-cyl car (or 'The Rule of 9' for a 4-cyl). 

For a 6-cyl car: subtract the number of the valve at rock from 13, then adjust the lash on that valve; e.g. if the number# 12 valve is at rock (spring compressed) adjust the lash on valve# 1, and so forth. 

Bob 


-------------------------------- 
Bob Spidell - San Jose, CA 

----- Original Message -----


Folks 
Valve adjustment, while very important, is not that complicated. We are trying 
to get the valve lash set at factory or aftermarket cam specs while the lifter 
is setting on the base circle of the cam lobe. Looking at a AH six cylinder 
cam you will see that the base circle is slightly more than 50 % of the cam 
lobe profile. The lifter contact area with the cam lobe is minimal even with a 
badly worn lifter. 

Another interesting factoid is that the first lobe on the cam shaft from the 
front, cylinder #1 exhaust is exactly 180 degrees off from the last cam lobe, 
cylinder #6 exhaust. This fact will make the valve adjustment process much 
less time consuming yet be as accurate. 

By bumping the starter with valve cover removed it is very easy to get the 
last valve spring from the back to completely compress, just watch it as your 
pushing the button on the starter solenoid, and then you set the lash on the 
first rocker arm from the front. Spin the starter to depress the second spring 
from the rear and adjust the rocker on cylinder #1 intake. Happens to be the 
second rocker from the front! You continue the process front to back to until 
all the valves have been adjusted. By the way don't get confused when you 
finish the third cylinder. I don't do the valves in that order but it makes it 
easier to keep track. This way you don't have to find top dead center on the 
pistons or concern yourself if you are off the timing mark by a few degrees. 
You can be off a lot and still be on the cam lobe base circle but using this 
method will produce very good results and it is a lot faster. Works on the 100 
four cylinder cars too. 

Aloha 
Perry