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Piston Assembly Set (4) Oversize +030 Austin Healey 100M

Performance
Part no:
ENG412B
Product name:
Piston Assembly Set (4) Oversize +030 Austin Healey 100M
Additional information:
Description:

Restore Compression After a +030 Rebore

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.

Key Benefits at a Glance

  • Maintains 100M compression (8.6:1) following a +030 rebore
  • Complete set: pistons, piston rings, gudgeon pins, circlips
  • Authentic dished crown for Le Mans-style builds
  • Precision cast aluminium for strength and reliability
  • Supports stable sealing and performance in rebuilt engines

Which Austin Healey Models Will These Fit?

Correct for engines rebored by 0.030 inch:

  • BN1 from chassis 221536 (100M high-compression specification)
  • BN2 100M high-compression engines

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.

What’s Included in the Set

  • 4 × High-compression pistons (+030 oversize)
  • 4 × Complete piston ring sets
  • 4 × Gudgeon pins
  • 4 × Circlips

Technical Details

  • Compression ratio: approx. 8.6:1
  • Size: +030 oversize (for 0.030 inch rebore)
  • Material: Cast aluminium alloy
  • Supplied as: Set of 4 pistons, rings, pins, and clips

Installation Guidance

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.

Why Choose This Piston Set?

Designed expressly for 100M engines, these +030 pistons provide the correct compression and crown geometry after machining, helping ensure lasting sealing and dependable performance.

FAQs

Do I need a rebore for these +030 pistons?

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.

What does “+030 oversize” mean?

The piston diameter is 0.030 inch larger than stock to match a cylinder bored by the same amount.

Are rings included?

Yes, each piston includes its ring set, plus gudgeon pin and circlips.

8.6:1 HIGH COMPRESSION

Application:
100M
Quantity per vehicle:
1
Items Per Pack:
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Your Price:
£321.27 Exc VAT
£385.52 Inc VAT
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