I'm often asked why we clay... what is clay you ask? Clay is exacty what you are thinking it is. We use crayola modeling clay. The kind you played with in Kindergarten.
Claying a motor is when you assemble it, typically with no gaskets (unless they are critical to dimensions) to make sure all of your clearances are correct. We have many "known" combinations of parts that we can trust, but anytime a new part is introduced we take the time to "clay". Basically, we build the engine twice!
In this case, we are going with a new configuration of piston with a known cam. Since it is a new piston, I wanted to ensure the high lift cam would clear the piston valve reliefs. Well in this particular case, the valves cleared with no problem! But... the pistons didn't clear the heads. We were "told" that the pistons would work with an unmodified 3.0L head. No dice. Looking at the clearance on the very outer edge of the piston, you can clearly see that this would have made for a very bad day if we had started this motor up. Fortunately (or unfortunately) the clay did its job. These pistons still require the "98mm chamfer" in the combustion chamber area of the head. While this certainly impacts the schedule, at least we didn't ruin a lot of new, very expensive parts in the process. I'm glad we found it sooner, rather than later. It's an easy fix and next time we will make sure to have the heads clearanced for this since I believe this is going to be a kick ass combo for Porsche 911SC upgrades!