Both the seven and eight port heads are suitable for any capacity "A" series engine from 850 cc and upwards.

The heads are cast from a virgin aluminium AA601.

Before machining the  alloy is heat treated to a T6 specification. This alloy exhibits good anti corrosion properties and has good welding characteristics (repairs easily in case of damage).

The heads are CNC machined and high chromium  valve seats inserts are shrunk in.

The combustion chamber volume can be reduced  by machining the head face by  up to 4mm.

The valve sizes are 36mm inlet and 30mm exhaust. The valves are custom-made from a 214N material and machined for maximum gas flow. They are longer than the standard valve, but still use the factory stem size of 9/32". A slightly modified factory valve guide is used for ease of replacement.

The 7 & 8 port heads will accept all after-market or factory parts including rockers, thermostat, thermostat housing, valve spring retainers, collets (keepers), temperature sender unit, and rocker cover.

The 7 port head uses standard exhaust manifold gaskets and will accept any Long Centre Branch or purpose built extractor designed to fit a cast iron 5 port head.

The eight port head requires a custom-made exhaust system and a separate flange plate is an available option.

The inlet ports are angled significantly and the shape modified to enhance the gas flow and increase air speed.

Options include:

• A cast aluminium inlet manifold suitable for both the 7 & 8 port cylinder heads for fitting twin Weber DCOE carburetors.
• A cast alloy rocker cover.
• A manifold plate is available for making the seven or eight  port exhaust extractor/header.