11. The twin-cam four-valve head was replaced by the single-cam three-valve head, possibly from the Arab. 12. The exhibited bike has an experimental larger valve head and a large aluminium crank pin. 13. The basic design is a revised 3VZ-E iron-block engine, mated with aluminum DOHC 24 valve heads . 14. The Sextet used a Continental side-valve six-cylinder, modified by National engineers with an overhead valve head . 15. The 2.4 litre engine gave rise to some massive power outputs using the 16 valve head . 16. Cosworth also produced a 16-valve head ( Cosworth Project DBA, 1987 ) for the Iron Duke. 17. Most often used is the valve head diameter. 18. It has aluminum four-valve heads , forged crankshaft, H-beam forged rods and aluminum pistons fed by a supercharger. 19. Various aftermarket manufacturers have also produced four-valve heads for the 302, notably Arao Engineering and Dominion Performance. 20. Later versions received a twelve-valve head , as installed in the JT150 Gemini it offered at 6, 000 rpm.
