shim confusion

to preface this, i am TERRIBLE at math. it just does not make sense in my brain.

ok, all my valves are tight. checked all the shims and using the formula in my clymer manual for which size shim to change to isnt making sense. ive got negative numbers and its not working.

for example: Exhaust valve on cylinder 1 measuered .102 or .10.
spec is .16-.2. so subtract .16 from .10 and i have Negative .06. the shim that was in there was a 250.

should i go down to a 245 shim?

also, did anyone else have to customize the shim tool? i had to bore out the one side so it would sit properly. i couldnt get it lined up with the holes on the head for two of the exhaust valves, cylinder 3 and 4. made the hole a bit bigger so i could bolt it down and it worked.

 

Here is the way to do it:

0.16 - 0.102 = 0.058 (this is how much too tight you are).

Subtracting from the 250 shim gives you the thickness you need to be at the tight end of the tolerance:

2.50 - 0.058 = 2.442

There is no 2.442 shim so you go to the next size down, 2.40 or 240.

 

Fonz in the forum xj faq suggestion big fitz has a complete break down of the valve adjustment inculding charts for exhaust and intake shims just find your measurement and current shim and it will tell you what you need (no math involved!!) just keep in mind that it is metric!!
Shaun

 

Carl, your way of doing the math made sense. thanks. and xj650ss, you just made me realize i was reading the chart wrong. i printed fitz's walkthrough and used it as a guide while i was checking the valves and until now, i was reading the chart wrong. i knew that if i took a step back and asked for help, things would pan out. thanks again.