The valve seats are excellent, not machined or lapped in far for excellent compression, valves are original 46mm intakes and sodium filled 40mm exhaust valves, same as the 73 Porsche 911 Carrera RS had, ports are large 38/38mm beautifully ported and polished, valve springs are new Aase Brothers /Aasco Motorsports with light weight titanium retainers, spark plugs are both 14mm for an easy selection of plugs, the heads have been chamfered/beveled for 86.7mm cylinders - these heads are perfect for your screaming 2.5 liter 911 engine. They were built for a 914-6GT 2.5 liter spare engine and plans changed. Freshly plated studs are included - not shown in the photos.…