Reinforced cylinder head gasket TVR Cerbera AJP8

The TVR engines covered

The TVR AJP8 (4.2 litre) and AJP8-4.5 (4.5 litre) eight-cylinder engines power the Cerbera. Each engine takes two cylinder head gaskets, one per bank of cylinders.

The manufacturer publishes nothing about the original gasket of these engines: not its part number, bore, construction or thickness. Designed for standard combustion pressure, it no longer suffices once that rises: the clamping force drops, the head lifts and coolant reaches a cylinder.

Reinforced cylinder head gaskets

Sealing a cylinder head does not depend on the gasket alone: the studs and nuts that clamp each head to the block contribute just as much. Check their condition and observe the specified tightening torque.

This page offers two part numbers from the American maker Cometic, a specialist in racing gaskets: H2790SP1043F for the left bank and H2789SP1043F for the right bank. Their bore is 91 mm and their thickness 1.09 mm. The construction is not stated in the data consulted. Each engine needs both part numbers, sold individually.

Technical specifications

A gasket's volume is the free space it leaves above each cylinder. It adds to the combustion chamber and lowers the compression ratio; only gaskets of the same bore can be compared.

Preparation and fitting

Before fitting, lay a straight edge across both heads and the block to check flatness, and have any warped surface machined.

Technical guide

The construction offered

Choosing bore and thickness

Gasket bore. The Cometic gaskets H2790SP1043F and H2789SP1043F are offered in 91 mm, with no other bore.

Thickness. The manufacturer gives no thickness for the original gasket of these engines: the removed gasket is the reference. The thicker the gasket, the larger the chamber and the lower the compression ratio; the thinner it is, the more the ratio rises.

As no original thickness is published, check with a dial gauge how far the pistons stand above the block face before fitting the 1.09 mm gasket: the measured gap gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc., founded in 1989 in Concord, Ohio, is an American company that designs gaskets and sealing solutions for engines. It made its name with the made-to-order gasket, cut to the bore and thickness required, built 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 91 mm bore of the gaskets 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: not published by the manufacturer.

Important: the part numbers on this page suit the TVR AJP8 and AJP8-4.5 engines of the Cerbera: each engine needs both, H2790SP1043F on the left and H2789SP1043F on the right.

Why switch to a reinforced gasket?

When the original gasket is no longer enough, the reinforced gasket takes over: the seal between head and block must hold under a higher combustion pressure.

On an engine whose power goes up, with a supercharger or turbo added or a higher compression ratio, the head gasket gives way first. A reinforced gasket avoids the leak, whereas removing both heads of an eight-cylinder is long and costs far more than the gasket.