Reinforced cylinder head gasket Ford V6 2.8 PR5 PR6 PR7

The Ford engines covered

The Ford Cologne V6 of 2.8 litres, identified by the codes PR5, PR6, PR7, PR8, PRB, PRC, PRD, PRG, PRN, PRT, PYA, PYN and PYU, powers the Capri III, Granada II, Sierra I and Sierra II listed below.

The original gasket of these engines carries the part number 6 140 740. Ford publishes neither its bore, nor its thickness, nor its construction. It is sized for the original combustion pressure: if it rises, the clamping load eases, the head lifts and coolant passes into a cylinder.

Reinforced cylinder head gaskets

Sealing does not rest on the gasket alone: the fasteners that clamp the head to the block count just as much. The CFM-20 combines a galvanized steel core with an asbestos-free compound applied to both faces.

This page describes the part numbers from the American maker Cometic, a specialist in racing gaskets, in a single construction: CFM-20. The bores are 92 and 95 mm and the thicknesses 1.09 and 1.5 mm. Each part number comes in a left-hand and a right-hand version, one per cylinder bank. By convention, the gasket bore is at least 0.5 mm larger than that of the cylinders. They are sold individually: one gasket per cylinder bank.

Technical specifications

The volume of a gasket corresponds to the hollow it leaves above each cylinder. That hollow adds to the combustion chamber: the wider it is, the lower the compression ratio falls. Compare only gaskets of the same bore, otherwise the comparison means nothing.

Preparation and fitting

Before fitting the gasket, run a straightedge across the head and block faces to check they are flat, and have them resurfaced if needed. An uneven face lets coolant or pressure escape, even with a reinforced gasket.

Technical guide

The construction offered

Choosing bore and thickness

Gasket bore. The Cometic CFM-20 comes in 92 and 95 mm, each in a left-hand and a right-hand version.

Thickness. Ford gives no thickness for the original gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

With no published original thickness, use a dial gauge to measure how far the pistons stand proud of the block deck, especially if the removed gasket is thinner than 1.09 mm: it shows the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American maker of engine gaskets and sealing solutions, set up in 1989 in Concord, Ohio. Its speciality is the made-to-measure gasket, cut to the bore and thickness requested. All manufacturing stays in the United States, from American raw materials.

Advantages over the original gasket

When a reinforced gasket becomes necessary

• Adding forced induction, or raising boost on an already turbocharged engine
• Cylinder rebored beyond what the 92 or 95 mm bore of the gasket offered covers
• Looking for a compression ratio different from standard, higher or lower
• Engine that has already lost its gasket, or is consuming coolant
• Competition use, where the gasket goes through repeated temperature rises

Vehicle compatibility

OEM part number: 6 140 740.

Important: the gaskets on this page are listed for the Ford V6 engines of 2.8 litres in the table (1977 to 1993). For any other vehicle, note the engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limits, this CFM-20 gasket takes over: its galvanized steel core holds its shape, while the asbestos-free compound seals the joint between head and block.

Adding a turbo or a supercharger, or raising the compression ratio, puts the head gasket under heavy strain: it is the weak link of the top end. A reinforced gasket rules out the leak and the head removal it forces, an operation far dearer than the part.