To drill a square or rectangular hole, score the material with a scribing iron or a sharp pencil, then punch one or more drill holes right next to each other depending on the required size and drill them out.
You are best using our step drill, which is specially designed for the combitech® dimensions, and afterwards file off the corners with a rectangular file.
More information: https://products.alfer.com
K20Z3, Cosworth Headgasket, A1 Technologies Head Studs, Dual Valve Springs & Ti Retainers, Skunk2 Header, 2.5″ Exhaust, Grams 550cc Injectors.
Tuned at Go Power Motorsports on 91 Octane – 2300ft. Elevation