BMC A Series

1.5 : 1 ratio

When contemplating the fitting of these rocker assemblies a few things must be anticipated.

Special "ball-ball" pushrods are required (for BMC B Series engines).

Valve clearances must be appropriately wider, (to maintain desired cam clearance).

Due to extra valve lift- check valve to piston / block clearance. Allow .100 to cater for rod and piston stretch and/or momentary timing variation due to over revving.

Check for valve spring coil bind at full lift.

The higher ratio rocker can control the valve train better (with a given valve spring pressure). Therefore, valve bounce speed is increased, or a lighter valve spring can possibly be used.

BMC B Series

1.5 : 1 ratio

1.6 : 1 ratio to Special Order

BMC B Series Roller Rockers

Apart from the increased ratio, this new set-up is a major departure from the traditional BMC design.

The standard rocker posts, shaft and rocker assembly are replaced by a substantial ‘girdle’ incorporating a restricted oil feed to each rocker arm (refer Note 1).

This ‘girdle’ bolts onto the head with 4 new head bolts and 2 new inter. bolts (supplied) once the existing studs have been removed.

Onto this is bolted individual rocker arm assemblies. Each rocker arm is fully machined from heat treated certified aircraft alloy extrusions. Fitted with large needle roller bearings mated to precision ground trunnions to reduce friction and increase engine power. Roller tips minimise valve stem and guide wear and give smoother, quieter operation (and can’t all ‘B’ Series stand improvement in this area). Correct geometry improves efficiency by ensuring the intended camshaft lift is transferred.

A giant step towards achieving our aim of rigidity and a reduction of reciprocating mass in the valve gear.