a bit thin. BLOCK PLANING might well hit the cylinder head! If 2.5mm/0.100in is removed If a Felpro gasket is going to be from the cylinder head of a standard Major gains are made if the block is fitted the block can be planed to a 2000 engine, the compression is planed. The reason for this is that the maximum of 0.75mm/0.030in which increased to, approximately, 12:1. The whole cross-sectional area of the bore will see the tops of the pistons protrud- main advantage of planing the cylinder is removed for every increment of ing 0.010in/0.25mm above the top of head by this amount is the fact that a planing, but when the cylinder head is the block deck. Removal of this high CR is possible while still using planed by the same amount, only the amount of material from a 2000 flat-topped pistons. smaller cross-sectional area of the engine block's deck will reduce the combustion chamber shape is combustion chamber volume by, removed. Block planing is almost approximately, 5cc. THINNER HEAD GASKET always carried out on a bare block Planing a 2000 block 0.75mm/ The standard head gasket is when the engine is being rebuilt. 0.030in, with no other changes, approximately 1.63mm/0.065in thick Note that the top of the piston on increases CR from 9.2:1 to 9.9:1. If a when compressed. The thickness of any standard engine is characteristi- Felpro cylinder head gasket is fitted to various aftermarket gaskets varies, but cally 0.5mm/0.020in down from the this engine too, the CR will be in- the thinnest compressed cylinder head top of the block. The minimum creased from 9.2:1 to 10.5:1, which is gasket is the Felpro blue head gasket clearance allowable between the top generally ideal for use with 97 octane which is 1.0mm/0.040in in thickness: a of the piston and the head surface of fuel. reduction of 0.6mm/0.025in. The the combustion chamber is 0.9mm/ If a head gasket thicker than the increase in compression is significant, 0.035in. Felpro item is going to be used, the particularly in combination with other Caution! - There is a proviso on amount of material that can come off methods. To ascertain the overall this size which is that this amount of the block can be increased proportion- thickness of the compressed head piston crown to cylinder head clear- ately. Caution! - This means that any gasket measure the uncompressed ance at top dead centre (TDC) is subsequent head gasket that is fitted gasket with a vernier caliper and designed for an engine turning a will have to be at least the same deduct 0.1 mm/0.004in from this maximum of 7500rpm. Another part thickness, otherwise the top of the thickness. of this proviso is that the engine must piston will come too close to the flat Reducing the thickness of the not have excessive piston to bore surface of the cylinder head. cylinder head gasket on a 2000 engine clearance. The higher the rpm the Consider having the tops of the by 0.125mm/0.010in reduces the engine is turned, and the greater the pistons 0.25mm/0.010in above the amount of combustion space by piston to bore clearance, the more block as a maximum so that any head 1.63cc. So using a Felpro gasket piston crown to cylinder head clear- gasket can be fitted in the future. reduces the combustion chamber's ance is required. This is because the You can assume that for every volume by 4cc, increasing the CR of a higher the rpm the more the connect- 0.25mm/0.010in removed from a 2000 engine from 9.2:1 to, approxi- ing rods stretch via the forces acting on 2000 engine block, the combustion mately, 9.7:1. Note that the Felpro them. The greater the piston to bore area volume is reduced by 1.63cc. gasket is made for the 2000 engine clearance, the more the piston 'rocks' The bore tops must be cham- and has an appropriate cylinder bore in the bore and the piston crown is fered after block planing so that aperture of 93mm: the gasket can be effectively higher in this 'rocking' pistons and rings are easy to fit with- used on the smaller Pinto engines, but situation (canted over at TDC). Allow out damage, and all holes, especially the potential compression gains will be a further 0.125mm/0.005in on the head bolt holes, must be deburred offset by the slight compression loss 0.005in to 0.006in piston to bore by countersinking after grinding. caused by the gaskets 'oversized' clearance engines, and a further cylinder aperture. 0.125mm/0.005in on engines turning up to 8000rpm. This means that the RAISED TOP PISTONS A considerable amount of mate- pistons can only be brought up flush rial can be removed from the Pinto There are plenty of raised top forged with the top of the block on some cylinder head gasket face without and cast raised top pistons available engines, otherwise the piston crowns detriment. which will allow very high CRs. Raised