This piston assembly set of 4 is engineered to the Austin Healey 100M high-compression standard. Supplied in +030 oversize, they maintain an approximate 8.6:1 compression ratio and suit engines rebored by 0.030 inch.
Correct for all 100/4 engines rebored by 0.030 inch.
Professional installation is strongly recommended. Confirm the final bore, set ring end gaps, and check piston-to-bore clearance. A piston ring compressor tool (TOL111) helps prevent ring damage and speeds assembly.
Designed expressly for 100M engines, these +030 pistons provide the correct compression and crown geometry after machining, helping ensure lasting sealing and dependable performance.
Yes. These are for engines rebored by 0.030 inch. If your wear measures less, consider +020; if still standard, use the standard size set.
The piston diameter is 0.030 inch larger than stock to match a cylinder bored by the same amount.
Yes, each piston includes its ring set, plus gudgeon pin and circlips.
8.6:1 HIGH COMPRESSION
