This piston assembly set of 4 follows the Austin Healey 100M high-compression specification. Supplied in +060 oversize, they maintain an approximate 8.6:1 compression ratio and suit engines rebored by 0.060 inch.
Correct for engines rebored by 0.060 inch:
Exclusions: Not suitable for early BN1 3-bearing engines prior to chassis 221536, or for standard low-compression 100/4 engines unless converted to 100M specification.
Professional installation is recommended. Verify wall thickness and clearance when machining to +060. Set ring gaps accurately and use a piston ring compressor tool (TOL111) to aid assembly and protect rings.
Developed specifically for 100M engines, these +060 pistons provide the correct compression and crown geometry at the largest common oversize, helping ensure sealing and durability where blocks allow.
Yes. These are for engines rebored by 0.060 inch. Check cylinder wall thickness and integrity before machining to this size.
The piston diameter is 0.060 inch larger than stock to suit cylinders bored by the same amount.
Yes, each piston includes its ring set, plus gudgeon pin and circlips.
8.6:1 HIGH COMPRESSION
