Reinforced cylinder head gasket Jaguar V12 7P 7P1 7S1 8B 8C 8E 8S XJ E-Type

The Jaguar engines covered

The Jaguar V12 of 5.3 litres, identified by the codes 7P, 7P1, 7S1, 8B, 8C, 8E and 8S, powers the Jaguar XJ, XJ Coupé, XJSC Convertible and E-Type Series 3 detailed below; the 8C also exists in 6.0 litres.

The original gasket of the Jaguar V12 carries the part numbers C33135 (right) and C33136 (left); the manufacturer publishes neither its bore nor its thickness. It is metal, fibre, metal, two sheets around a fibre core, and sized for standard combustion pressure: when that pressure rises, the head loses clamping force, lifts and lets coolant reach a cylinder.

Reinforced cylinder head gaskets

The gasket does not guarantee the seal on its own: the fasteners that clamp the head onto the block weigh just as much. CFM-20 combines a galvanized steel core with a soft asbestos-free compound that makes up for small irregularities in the gasket faces. On this V12, torquing in several passes keeps the pressure even.

This page offers the part numbers from the American maker Cometic, a specialist in racing gaskets, in a single construction: CFM-20. Their bore is 93 mm or 97 mm and their thickness 1.09 mm or 1.50 mm, for the left bank and for the right bank. Each part number is sold individually.

Technical specifications

A gasket's volume is the space it leaves free above each cylinder. That space adds to the combustion chamber and lowers the compression ratio; only gaskets of the same bore are comparable. Here, the gaskets come in two bores, 93 mm and 97 mm.

Preparation and fitting

Before fitting, run a straight edge over the head and the block to check their flatness, and have either one resurfaced if necessary. Cometic checks the flatness of each of its CFM-20 gaskets. This check holds for the Jaguar V12 as for any other engine.

Technical guide

The construction offered

Choosing bore and thickness

Gasket bore. The Cometic CFM-20 gasket is offered in 93 mm (C4330 on the left, C4331 on the right) and in 97 mm (C4221 on the left, C4222 on the right), each in 043 (1.09 mm) and in 059 (1.50 mm).

Thickness. For the original gasket, the manufacturer gives no thickness. 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, read with a dial gauge how far the pistons stand above the block's gasket face, bank by bank, above all if the removed gasket is thinner than 1.09 mm: this value gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American manufacturer of gaskets and sealing solutions for engines, founded in 1989 in Concord, Ohio. Its reputation rests on the made-to-measure gasket, cut to the bore and thickness requested; all production takes place in the United States, from American raw materials. The part numbers C4330, C4331, C4221 and C4222 are its own.

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 93 mm or 97 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: C33135 (right) and C33136 (left).

Important: the part numbers on this page suit the Jaguar V12 7P, 7P1, 7S1, 8B, 8C, 8E and 8S: a V12 has two banks and each takes its own gasket, so order one left and one right part number, and check your engine's bore, 93 mm or 97 mm.

Why switch to a reinforced gasket?

When the original gasket reaches its limits, this CFM-20 gasket takes over: the steel core keeps its shape under combustion pressure, while the soft compound on both faces follows the small flaws of the head and block. The Jaguar V12 finds here eight part numbers, in two bores and two thicknesses, for each bank.

On an engine driven to its limit, the head gasket is the first part to fail, the weak point of the top end. A reinforced gasket prevents the leak, whereas the head removal that follows, a long and delicate job, costs much more than the gasket. This holds for the Jaguar V12 as for any hard-driven engine.