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BY REFERENCE COMETIC - Reinforced cylinder head gaskets
Manufacturers
BY REFERENCE COMETIC - Reinforced cylinder head gaskets
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Reinforced Cometic head gasket. Sold individually, one gasket per engine.
The Coventry Climax FPF Mark 2 (code FPF) is a 1.5 litre four-cylinder (1,500 cc, 82 mm bore, 71 mm stroke) with twin overhead camshafts, developed in 1961 for the 1.5 litre Formula One, where it produced 151 hp.
The manufacturer publishes nothing on the original gasket of this racing engine: neither its part number, nor its bore, nor its construction, nor its thickness. It was sized for the combustion pressure of the day; if that rises, the clamping load fades, the head lifts and coolant seeps into a cylinder.
The gasket does not seal alone: the fasteners that clamp the head onto the block count just as much. CFM-20 pairs a galvanized steel core with a soft asbestos-free compound that makes up for small irregularities in the gasket faces.
This page presents the part number from the American maker Cometic, a specialist in racing gaskets, in a single construction: CFM-20. Its bore is 82 mm, the same as the cylinders of the FPF Mark 2, and its thickness 1.50 mm. It is sold individually: one gasket per engine.
| Gasket bore | Thickness | Gasket volume | Gasket type OEM not specified | Brand | Part number |
| 82 mm | 1.50 mm | 7.92 | CFM-20 | Cometic | C4267-059 |
A gasket's volume is the space it keeps free above each cylinder. It adds to the combustion chamber and reduces the compression ratio; only gaskets of the same bore can be compared.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts | FPF | not published by the manufacturer |
Before fitting, check the flatness of the head and block with a straight edge, and have either one resurfaced if needed. Cometic checks the flatness of each of its CFM-20 gaskets.
| CFM-20 Cometic A galvanized steel core, covered on both faces with a soft asbestos-free compound of aramid fibres, mineral fillers and elastomer binders. This layered construction, halfway between metal and fibre, joins the strength of steel to the suppleness of the compound. It is offered here as a single gasket, with an 82 mm bore and a thickness of 1.50 mm. |
Gasket bore. The Cometic CFM-20 gasket is offered in 82 mm (C4267-059), with no other bore.
Thickness. For the original gasket of this engine, no thickness is published. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.
| Your goal | Thickness to choose |
| Keep the original compression ratio | Original thickness not published: read that of the removed gasket and set it against the only gasket offered, 1.50 mm |
| Skimmed cylinder head, make up the lost height | Only one thickness exists, 1.50 mm: compare it with that of the removed gasket, plus the material taken off at resurfacing |
| Forced induction build, lower the ratio | 1.50 mm, if the thickness read on the original gasket at removal is lower |
| Naturally aspirated build, raise the ratio | 1.50 mm, if the thickness read on the original gasket at removal is higher |
With no published original thickness, use a dial gauge to measure how far the pistons stand above the block's gasket face, especially if the removed gasket is thinner than 1.50 mm: this gives the clearance left between piston and head.
 | Cometic Gasket, Inc. is an American maker of gaskets and sealing solutions for engines, founded in 1989 in Concord, Ohio. It made its name with the made-to-measure gasket, cut to the bore and thickness requested, and makes everything in the United States from American raw materials. |
| Criterion | Original gasket, part number not published | Reinforced gaskets |
| Construction | Construction not stated by the manufacturer | Galvanized steel core and asbestos-free compound (CFM-20) |
| Gasket bore | not published by the manufacturer | 82 mm |
| Thicknesses available | thickness not published by the manufacturer | 1.50 mm |
| Compression ratio adjustment | None | Through the thickness chosen |
| Resistance to overpressure | Limited to standard output | Designed for forced induction |
| Model | Engine code | Power | Years |
| Coventry Climax FPF Mark 2 1.5 (Formule 1, 1961) | FPF | 151 hp | 1961 |
OEM part number: not published by the manufacturer.
Important: the part number on this page suits the 1.5 litre Coventry Climax FPF Mark 2 engine: check that your engine is an FPF Mark 2 before ordering.
When the original gasket reaches its limit, this CFM-20 gasket takes over: the steel core holds its shape under combustion pressure, and the soft compound on both faces follows the small flaws of the head and block.
On a hard-driven competition engine, the head gasket is the first part to give way, the weak point of the top end. A reinforced gasket rules out the leak, whereas the head removal that follows costs far more than the gasket.
