Piston Rings and Sizes
Engine and Bore Size Ring including oil ring
and ring size 		Ring Hepolite part number. Rings Rover part number STD/20 only Piston Part Number Piston shape Remarks
850cc
62.916mm 2.477” STD 20/ 30/ 40/ 60		 4.
3 x 0.0700”
1.778mm
1 x 0.1250”
3.175mm 		RA8576
BHM1161
12A120
 
 Use 15037
5.
3 x 0.0700”
1.778mm
1 x 0.1248”
3.170mm
1 x 0.1250”
3.175mm		 RA8577

 

 15037

  

  
Cooper - 997cc
2.458” - 62.43mm
STD 20/ 30/ 40/ 60		 4.
3 x 0.0625”
1.588mm
1 x 0.1250”
3.175mm
  		2C6724
Hastings ring
  

 12A212
15799
18515 		 

  
Cooper
998cc
2.542”-64.567mm
STD 20/ 30/ 40/ 60		 3.
2 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm		 R39400
can use R33636 		 
 20950
was 18516 		Flat top 20950
9.7 CR		 Powermax
Rings also fit 18516
4.
3 x 0.0625”
1.588mm
1 x 0.1250”
3.175mm 		R32026
or C-STN99 		BHM1162
 12A674
 Flat top with
raised ‘D’ 		 
998cc
64.567mm
2.542”
STD 20/ 30/ 40/ 60		 4.
3 x 0.0625”
1.588mm
1 x 0.1250”
3.175mm		 R32026
or C-STN99 		BHM1162
12A673 / 16309
 Dished piston 8.3
To 1979
4.
3 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R33636
BHM1281
ADU3920
20754 		Flat top 10.3 to 1 CR
 1980 on, until changed
to 3 ring piston
4.
3 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R33636
BHM1281
ADU3922
20773 		Dished 8.3 to 1 CR
3.
2 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R39400
can use R33636 		BHM1415
ADU3490
Flat top 10.3 to 1 CR
3 ring pistons up to
introduction of press
fit gudgeon pin, 1988
3.
2 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R39400
can use R33636 		BHM1415
 ADU4203
20536 		Dished 8.3 to 1 CR
3.
2 x 0.0590”
1.499mm
1 x 0.1181”
3.000mm 		  BHM1629
 TAM2052 (Rover)
P22463 (AE) 		Flat top stamped 21964
 Press fit gudgeon pin
only 1989 on
3.
2 x 0.0590”
1.499mm
1 x 0.1181”
3.000mm 		R43240
   TAM2054 (Rover)
22464 (AE) 		Dished stamped 21965
1100cc
64.567mm
2.542”
STD 20/ 30/ 40/ 60
 
  		4.
3 x 0.625”
1.588mm
1 x 0.1249”
3.172mm		 R32026
or C-STN99 		BHM1162
 12G758
use 20397 		 
 Morris Minor/ Mini/ MG 1100/ Sprite
Clubman 1975-1980
5.
3 x 0.0625”
1.588mm
2 x 0.1250”
3.175mm 		R17927
  
 Not Mini
16179 		 
 Morris Minor/MG 1100/Sprite
5 ring 1975-1976
4.
3 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R33636
20397 		BHM4418
  
Dished
20397 		Morris Minor
MG 1100/Sprite
1275cc
70.625mm
2.780”
STD 20/ 30/ 40/ 60		 4.
3 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R21576
 BHM1164
 17271 (AE)
   1275GT and
1275cc non ‘S’
4.
3 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R21576
 BHM1284
 20394 (AE)
 Dished 8.8 CR
1275GT and
1275cc non ‘S’
3.
2 x 0.0591”
1.501mm
1 x 0.1575”
4.000mm 		R35960
  
   Dished 8.8 CR
 Latest metric sized piston
1275 GT 1970-1975
4.
3 x 0.0469”
1.191mm
1 x 0.1575”
4.000mm 		R19520
 BHM1165
STD/20 oversize 		AEG143
 Dished 9.7 CR Original ‘S’ and
1300GT. Use 21253
3.
2 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		R26686
use R21576 		BHM1166
 19320
 Dished 9.7 CR
 Later ‘S’ and
1300GT / 1275GT
3.
2 x 0.0591”
1.501mm
1 x 0.1181”
3.000mm 		R41570
C1818 (Steel ring upgrade) 		BHM1628
 21253 (AE)
TAM2050 (Rover) 		Dished 9.7 CR
 
Stamped 21962 		Metric sized pistons
Dished 10.1 CR
3.
2 x 0.0591”
1.501mm
1 x 0.1575”
4.000mm 		R35960
  
 21250 (AE)
TAM2048 (Rover) 		Dished 9.4 to 1 CR
Stamped 21963 		Metric sized pistons
3.
2 x 0.0625”
1.588mm
1 x 0.1575”
4.000mm 		Use R21576
 BHM1260
 ADU5704
was P22357 		Turbo Dished 9.4 to 1 CR
Known as 21254 		Use P223575 + 40 only available
2 x 0.0470”
1.194mm
1 x 0.1575”
4.000mm 		C-AJJ3379
  
 ADU5704
was P22357 		Turbo Dished 9.4 to 1 CR P223575 + 40 only
AE MEGA type
2.780”
70.625mm
Powermax
STD
+20/40/60 		3.
2 x 0.0469”
1.191mm
1 x 0.1575”
4.000mm 		R39380 C.W.E
Can use R19520 		 
 18517
18518 		Dished 9.7 CR
Flat top 		Forged, use 20747
Use 21882
3.
2 x 0.0469”
1.191mm
1 x 0.1575”
4.000mm 		R39380 C.W.E
Can use R19520 		 
 20747
 6.6cc Dish
9.7 to 1 CR 		AE413
Squeeze cast - 16906
3.
2 x 0.0469”
1.191mm
1 x 0.1575”
4.000mm 		R39380 C.W.E
Can use R19520 		 
 20739
 Flat top
 Squeeze cast,
use 21882
3.
1 x 0.0394”
1.000mm
1 x 0.0469”
1.191mm
1 x 0.1181”
3.000mm 		R41720

  

 21882

 Flat top

 Squeeze Cast
AE-MEGA / OMEGA
2.780mm 		2 x 0.0470”
1.194mm
1 x 0.1575”
4.000mm 		C-AJJ3379
  
 C-AJJ3378 AE/MEGA
C-AJJ3382 AE/MEGA 		Dished
Flat top 		OMEGA are Hi-grade cast light alloy.
AE MEGA were squeeze cast - now
new technology castings, FM-B2
material double heat treated
AE-MEGA / OMEGA
73.5mm 		2 x 0.0470”
1.194mm
1 x 0.1575”
4.000mm 		OMEGA
R73.5 		 
 See special tuning
 7cc dish - C-STR310
11cc dish - C-STR312
Powermax 73.5mm
1275 to 1380cc 		2 x 0.0591”
1.501mm
1 x 0.1575”
4.000mm 		R39390
  
 P20659 (AE)
C-STR311 (Minispares) 		Dished 9.6 CR
9cc Dish