These Porsche 912 cylinder heads were modified by Xtreme Cylinder Heads of Palm City, Florida, in 2012 for a twin-plug configuration with an emphasis on increased performance. They are offered at no reserve with distributors in Flagstaff, Arizona.
The above invoice details more than $5,000 in work completed on the heads.
Machine work involved welding aluminum plugs into the heads and repairing one combustion chamber. The combustion chambers were measured and equalized to a volume of 61 cc each. The heads were deburred, washed, and assembled with stainless-steel 38 mm intake valves, 35 mm exhaust valves, bronze valve guides, and competition-style valve seats. The valvetrain comprises PAC dual valve springs, PAC titanium retainers, and Ferrea K10114 valve locks. Counterbores were machined for use with 86 mm pistons.
Two prototype distributors are included, and the seller notes that only one is required to set up the system. A programmable CDI unit will also be required. A six-pin engine wiring harness, a cap, and a rotor are included.