By Jim Tapp
Originally published in Talkin' Tech October 2008
One of the things that I stressed to my students when I taught at Austin Technical College was the importance of measuring BEFORE starting to machine. Many of my students didn't get why they should go through all of that trouble. After all, measuring isn't fun. Machining is. My answer to them was (and still is) how are you going to know what you have if you don't measure up front?
You can't always take your customer's word for it that a head hasn't been machined. He may have bought it used from someone who didn't bother to tell him that the head had been resurfaced, the guides replaced or oversize valve stems installed. By just taking his word for it, instead of measuring, you won't know until you're done machining that things just don't add up.
You've probably heard the saying in carpentry, "Measure twice, cut once." Well it's just as (or maybe more) important in engine machining. After all, if you cut a stud a little short, you can always run to the nearest home center to get another one for a few dollars. Cylinder heads aren't as readily available or as inexpensive.
Take my advice, I've been doing this for a long time (nearly 50 years). Measure BEFORE you machine then measure while you machine and measure when you reassemble.