How do I measure cylinder to see how much has been milled off???

This is a small block J head.

What's the casting number on the runner. I'll check mine and measure them.

Do you have a set of calipers?


What you're going to need to do is find someone with the same casting as yours that has not been milled. Measure with dial calipers from the valve cover rail to the head deck

Spark plug side I'm assuming?