Our engine came with one of Richard Longman’s highly regarded cast-iron heads. They’re known for their excellent flow characteristics. The task of adapting the Honda-based valvetrain components to the Longman head was handled by Mark De Groff, a longtime secret weapon for many successful vintage racers. De Groff made special guides to accommodate the 5.5mm valves and topped them with Viton seals. He also set the springs to the proper installed height, providing the required tension per the camshaft manufacturer’s specs

Containing the Combustion

Sealing the combustion chamber is, of course, critical for any high-performance engine. The A-series is notorious for blowing head gaskets, so we needed to optimally distribute the clamping load. We’d make arrangements while the head was off.

The 1275cc block originally came with nine head studs, but later versions had 11. Since the head was designed to accommodate those 11 studs, it’s a fairly easy task to machine the block to accept the additional two studs. ARP sells a head stud kit for this application.

ARP’s head studs are made of a heat-treated chrome moly–200,000 psi tensile strength–and have a significantly higher safety margin than the original hardware. Even so, cranking up the preload too much can be detrimental to the gasket.

While the cylinder head was off, we didn’t machine its face any further. Upping an engine’s compression by shaving down the cylinder head’s mounting surface is certainly a path to increased power, but it comes with added cylinder pressure and potential head gasket issues. Our engine already had a 12.22:1 compression ratio, so we decided to keep things status quo.

Procuring New Pistons

The engine carnage that put us out of the race resulted in two damaged pistons, so we decided to replace them with exactly what we already had: JE forged-aluminum flat-top pistons. Ours have a 1mm top ring, 1.22mm second ring and 2.82mm oil ring.