Triple-Digit Displacement | Kuryakyn 103ci Hop-up, Part 2

Get Squished:

08. With the upper rocker box housings in place and torqued and the pushrods properly adjusted, the engine build portion was complete.

08. With the upper rocker box housings in place and torqued and the pushrods properly adj

Setting Squish

To get optimal performance out of an engine build, it’s important to set the proper squish band. The squish band is the area between the top of the piston and bottom of the cylinder head when the piston is at top dead (TDC) center on its compression stroke. As the piston reaches TDC, the air fuel mixture is compressed creating turbulence in the combustion chamber. More turbulence is preferred as it helps achieve better atomization of the fuel for better combustion, less detonation, and results in a more efficient/powerful burn, more power, and better fuel efficiency. Too tight of squish band can result in the piston hitting the head, while a loose squish band can result in less than optimal turbulence and atomization, resulting in detonation/pinging and less power. As they say there’s more than one way to skin a cat and many engine builders have their own way of setting squish. Here’s Mike Roland’s method:

09. Kazoo then turned his attention to installing the Hi-Five Mach 2 intake kit. The kit comes with everything needed for installation: outer cover, high-flow filter, backing plate, hardware, breather hoses, breather bolts, air lock ring, dual velocity ring, and support bracket (not shown).

09. Kazoo then turned his attention to installing the Hi-Five Mach 2 intake kit. The kit

I set the squish at 0.030 to 0.035 inch. I use 0.060-inch solder, or close to it, on the top of the piston to measure. I cut six pieces about 1/2 inch long for each piston. I then place a piece over the wrist pin on the top of the piston on each side and then the other pieces just ahead and behind this point. I use a small piece of modeling clay to keep the pieces in place. The six pieces of solder are now arranged to contact the quench area of the head when it is mounted in place. I then mount the head on the cylinder with a head gasket in place, I start with a 0.045-inch gasket. I then torque the head bolts to spec and manually turn the engine over a couple of times. The first revolution will turn a little hard when the solder contacts the head. After a couple revolutions I remove the head and use a micrometer or a caliper to measure the thickness of the solder. I measure all six pieces, add the measurements together, and divide the answer by six, and that number is the squish. I then adjust the head gasket thickness to get the squish to the desired 0.030- to 0.035-inch measurement.