Head Gaskets

Has your engine been bored out, had the cylinder head skimmed or been given more boost, so the original gasket no longer suits the project? Here you will find head gaskets in several bore sizes and thicknesses for e.g. Honda and BMW engines as well as Ford and GM V8s – for you who are building or rebuilding your engine.

How to choose the right head gasket

The head gasket seals between the engine block and the cylinder head and must keep combustion pressure, coolant and oil separated. Tuned engines typically use MLS gaskets – gaskets made of multiple layers of steel – such as Cometic's MLX and MLS gaskets for engines like the Honda F20C, BMW B58 and M50/M52 and Ford 289/302/351. The category also includes brands such as Fel-Pro, Wiseco, JE Pistons and Supertech.

• Engine code and bore: The gasket must match the engine code and the cylinder diameter, including after any reboring. The bore size is stated in the product name, e.g. 81, 83.5 or 85 mm.
• Thickness: Thickness affects the compression ratio and the clearance between piston and cylinder head. A thicker gasket can lower compression, e.g. for higher boost, but the right choice depends on the pistons, cylinder head and the engine's other dimensions.
• Surfaces: MLS gaskets typically require flat and smooth surfaces, so checking or skimming the block and cylinder head may be necessary.

Follow the manufacturer's torque specifications and tightening sequence during installation. With the cylinder head off anyway, it can make sense to replace the valve cover gaskets and intake manifold gaskets at the same time – or choose a complete engine gasket set.

Frequently asked questions

How thick should the head gasket be?

It depends on the engine's compression ratio, piston height, whether the block or cylinder head has been skimmed, and how much boost you run. Measure or calculate compression and piston-to-head clearance before choosing a thickness.

Should the gasket bore match the cylinder diameter exactly?

The gasket bore is typically chosen equal to or slightly larger than the cylinder diameter, so the edge does not protrude into the combustion chamber. If the engine has oversize pistons, the gasket must match the new bore.

Can I reuse the head bolts when replacing the gasket?

Many original head bolts are torque-to-yield bolts that must not be reused. Follow the engine manufacturer's instructions, and consider new bolts or studs if the engine will run higher cylinder pressures.