The Original Austin Healey Parts Specialist
OFF
VAT
>
>

Piston Assembly Set (4) Standard Size Austin Healey 100M

Performance
Part no:
ENG412
Product name:
Piston Assembly Set (4) Standard Size Austin Healey 100M
Additional information:
Description:

Restore Correct Compression for Your 100M

This piston assembly set of 4 is built to the high-compression specification of the Austin Healey 100M. Supplied in standard bore size, they deliver an approximate 8.6:1 compression ratio with the correct dished crown design used in factory 100M and Le Mans upgrades.

Key Benefits at a Glance

  • Restores factory-spec 100M compression ratio (8.6:1)
  • Direct replacement for standard bore engines
  • Complete with piston rings, gudgeon pins, and circlips
  • Correct crown profile for authenticity in Le Mans upgrades
  • Durable cast aluminium alloy for long-term reliability

Which Austin Healey Models Will These Fit?

These pistons are correct for the following engines:

  • 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
  • 4 × Complete piston ring sets
  • 4 × Gudgeon pins
  • 4 × Circlips

Technical Details

  • Compression ratio: approx. 8.6:1
  • Size: Standard bore
  • Material: Cast aluminium alloy
  • Supplied as: Set of 4 pistons, rings, pins, and clips

Installation Guidance

Professional installation is strongly recommended. Ensure correct piston ring gapping, cylinder clearance checks, and careful fitting. To make the job easier and avoid ring damage, we recommend using a piston ring compressor tool (TOL111) during assembly.

Why Choose This Piston Set?

Unlike generic alternatives, this piston set is engineered specifically for the Austin Healey 100M. It ensures the correct compression ratio, crown shape, and durability, making it the right choice for restorers and rebuilders.

FAQs

Do these pistons include rings?

Yes, each piston comes with a complete ring set, gudgeon pin, and circlips.

What compression ratio do they provide?

They deliver approximately 8.6:1 compression ratio, as used in the original 100M specification.

Do I need a rebore for these pistons?

No. These are standard size pistons for blocks still within original bore tolerance. Oversize versions are available for rebored engines (+020, +030, +040, +060).

Which engines are excluded?

They do not fit early BN1 3-bearing engines before chassis 221536 or standard low-compression 100/4 engines unless converted to 100M specification.

8.6:1 HIGH COMPRESSION

Application:
100M
Quantity per vehicle:
1
Items Per Pack:
???
5b40aec9-3465-40f0-b271-ff08d0b36ef8
0
Add to wishlist
WL
+
Your Price:
£321.27 Exc VAT
£385.52 Inc VAT
Quantity:
Cart
+

Related Products

Big Healey
Part No: ENG401C
1A
Application: BN1 - BN2
Competition Steel Gasket - cylinder head
Buy Competition Steel Gasket - cylinder head Online
£192.96
View
Big Healey
Part No: ENG404
2
Application: BN1 - BN2
Bolt - con rod - PAIR
Buy Bolt - con rod - PAIR Online
£30.59
View
Big Healey
Part No: ENG406
4
Application: BN1 - BN2
Bolt - small end
Buy Bolt - small end Online
£1.38
View
Big Healey
Part No: ENG417
7
Application: BN1 - BN2
Cylinder Liner
Buy Cylinder Liner Online
£30.87
View

Welcome!

It appears you are visiting us from
United States
Would you like to shop and see all prices specific to your Country?
YES PLEASE
NO THANKS
Top