turned down to allow the fitting of a Sierra Cosworth-type auxiliary drive sprocket. While the standard Cosworth drive belt is almost always adequate, stronger belts are available. Burton Power, for example, offers a high strength belt which has carbon-fibre in it. These belts are slightly wider than the standard ones but still fit the standard drive sprockets. CYLINDER HEAD PORTING Caution! - The porting work (to the dimensions which follow) must by carried out by an experienced professional as, in some areas, wall thickness gets thin and a mistake could cause breakthrough. The inlet valve guides do not need to be removed Auxiliary driveshaft (left) nose has been turned down to take a genuine Sierra Cosworth during porting work but there's no sprocket (right). piston pin retention method can be used. The crown of the piston will, of course, be 1.5mm down the bore more than usual, since the Cosworth connecting rods are 1.5mm longer. The block can be planed to increase the compression (1.5mm/0.060in with complete safety). If 11.8 to 1 or 12 to 1 pistons are fitted into a standard Pinto short assembly, the fact that the piston crowns are down the bore means that a sometimes useful reduc- tion in compression is the result. The Inlet port with right-hand tract opened out. planing of the block by 1.0mm/ 0.040inch might well prove to be a more appropriate amount. COSWORTH HEAD/PINTO BLOCK CAMSHAFT DRIVE MODIFICATIONS If a Sierra Cosworth cylinder head is fitted to a Pinto block the crankshaft sprocket has to be changed to a Sierra Cosworth-type to suit the Cosworth drivebelt (which must be used) and the Pinto auxiliary shaft will have to be Completed inlet port viewed from manifold end..