As far as cylinder head work goes, a little mild porting was done. Aside from blending the valve seats, a little massage work was done on the short turn radii on the intake side, and the exhaust ports (aside from the seats) are mostly left alone. Once again, we’re looking for mid-range torque, and the valve seat blending helps boost the low-lift flow so critical to building power in the desired rpm range. We’re sticking with stock valves at this point, along with a fresh three-angle valve job on the seats – paying close attention to the width of the seat cut. Keeping the ports small and efficient maintains the velocity of flow, and we’re going to start with a stock intake manifold as well so that we have long narrow intake runners. In order to gain more compression we shaved the head – keeping in mind that we wanted to optimize squish clearance, which plays a huge factor in promoting a thorough combustion cycle while reducing the risk of detonation.
Once the head was assembled, we needed to check for sufficient piston to valve clearance. Lots of people use clay – but clay is tricky to work with, and it’s hard to be consistent, especially when you’re trying to measure things to thousandths of an inch. I do use a little clay – but not to measure clearance. I use it to hold pieces of soft electrical solder in place. Solder is soft enough that it will deform when you rotate the engine by hand, and it holds its shape exactly after deformed. It’s a great way to accurately measure squish clearance too. A word of caution – when rotating the engine through TDC with the solder in place, I like to do it in steps – apply a little pressure after you feel interference, back up a little, then bring it up again and apply a little more pressure. Usually, it only takes two or three steps. This gradually flattens the solder without undue force, especially if the solder is a lot thicker than needed. With the solder “tacked” in place with bits of clay, we installed the cylinder head with a used gasket and torqued it in place.