Additional NotesThese aluminium cylinder heads have had many years of designing, testing and researching go into them. The quality of the machining is second to none and they are all polished, ported and ready to fit with the valves installed. These heads will make a big difference to the performance of your car. They have been fitted and tested on all manor of engines from fast road to full race and the results have been in line with the high quality of the product.