Determining Ring Gap
To determine the ring end gap look for your application in the proceeding table.
ALL BORES MUST BE CONVERTED TO INCHES.
Example: Bore size is 81 mm — to find top ring end gap for a street application:
81 mm/25.4= 3.189 inches
(3.189" x .005)= .016"
0.016" is the minimum allowable clearance.
NOTE
If the ring gap is less than the minimum specified for your bore size, it will be necessary to file fit the rings to achieve proper end gap.
Ring Filing Procedures
1. Ring gap should be filed using a ring filing tool.
2. Ring gap should be filed in an inward direction and square to the sides.
Important: Ring sets are manufactured to fit specific bores.
For every 0.001" over the intended bore size, ring gap will increase by 0.003142"
Failure to check ring gap can result in severe engine failure.
The following end gap recommendations are general guidelines.
The best ring gap for any particular engine and application varies.
Increased clearance is generally needed for forced induction, nitrous, filled blocks, endurance racing and other extreme applications.
The final end gap suitable for the engine is the full responsibility of the engine builder.
If you have any questions, please call 949-567-9000 for technical support.
Ring End Gap Chart
Ring gap measuring procedures
1) A torque plate should be installed on the engine cylinder block (if applicable) and torqued to the same specifications as machine shop.
2) Piston ring should be below and square to the deck
3) Measure ring gap with feeler gauge
A torque plate must be utilized for boring and honing*
GAS NITRIDED, CPN, CPN2 AND R8GNHD PISTON RINGS
To identify a gas nitrified top ring the entire ring will be a light gray.
These instructions must be followed for maximum ring seal.
A torque plate must be used unless the bolt holes are not part of the cylinder.
The first stone is a 525 (220 grit) stone, done until there is .001 " left from final bore.
The bore must be round to .0002", checked 360 degrees from the bottom to the top of the bore.
Then switch to a 625 (280 grit) stone, 50% load until .0002" is left from final bore.
Then use the 625 stone at 20% load to final bore size.
DUCTILE MOLY RINGS
To identify a moly top ring look for a silver-grey plated finish with black phosphated top and bottom surfaces.
If there is a dot on the flat side of the ring, make sure it faces up.
Rough hone cylinders to within .003", intermediate hone to within .0005" with 220 grit and final hone with a 400 grit and a 10 to 12 RA finish with a 20° to 22° crosshatch.
CHROME RINGS
To identify a chrome top ring the face will have chrome plating, the top and bottom of the ring will be a reddish-brown.
Chrome on any of the rings is not advisable with nikasil bores.
These instructions must be followed for maximum ring seal.
A torque plate must be used unless the bolt holes are not part of the cylinder.
The first stone is a 525 (220 grit) stone, honed until there is .001" left from final bore.
The bore must be round to .0002", checked 360 degrees from the bottom to the top of the bore.
Continue with a 525 (220 grit) stone, 50% load until .0002" is left from final bore.
Then use the 525 stone at 20% load to final bore size.
ALL RINGS
The honing must be done slow to minimize heat build-up. No hand honing.
Final bore needs to be less than plus or minus .0002" out of round, checked 360 degrees around the bore from the bottom to the top of the cylinder.
This should be checked with a dial bore gauge.
The expertise of your machine shop is critical to the proper finish on your block bore.
When you receive the block back from the machine shop it will appear clean, the block still needs to be cleaned.
There could be material trapped in the honing grooves of the block that are not visible.
Failure to clean the block could lead to premature ring wear and blow-by.
To determine the ring end gap look for your application in the proceeding table.
ALL BORES MUST BE CONVERTED TO INCHES.
Example: Bore size is 81 mm — to find top ring end gap for a street application:
81 mm/25.4= 3.189 inches
(3.189" x .005)= .016"
0.016" is the minimum allowable clearance.
NOTE
If the ring gap is less than the minimum specified for your bore size, it will be necessary to file fit the rings to achieve proper end gap.
Ring Filing Procedures
1. Ring gap should be filed using a ring filing tool.
2. Ring gap should be filed in an inward direction and square to the sides.
Important: Ring sets are manufactured to fit specific bores.
For every 0.001" over the intended bore size, ring gap will increase by 0.003142"
Failure to check ring gap can result in severe engine failure.
The following end gap recommendations are general guidelines.
The best ring gap for any particular engine and application varies.
Increased clearance is generally needed for forced induction, nitrous, filled blocks, endurance racing and other extreme applications.
The final end gap suitable for the engine is the full responsibility of the engine builder.
If you have any questions, please call 949-567-9000 for technical support.
Ring End Gap Chart
| APPLICATION | TOP RING | SECOND RING | OIL RING |
| Street/Hi performance | Bore x 0.0045" | 0.004" - 0.008" bigger than top ring | Min 0.015" Do not file |
| Drag racing Street racing |
Bore x 0.005" | 0.004" - 0.008" bigger than top ring | Min 0.015" Do not file |
| Nitrous/Turbo Supercharged |
Bore x 0.0055" | 0.004" - 0.008" bigger than top ring | Min 0.015" Do not file |
Ring gap measuring procedures
1) A torque plate should be installed on the engine cylinder block (if applicable) and torqued to the same specifications as machine shop.
2) Piston ring should be below and square to the deck
3) Measure ring gap with feeler gauge
A torque plate must be utilized for boring and honing*
GAS NITRIDED, CPN, CPN2 AND R8GNHD PISTON RINGS
To identify a gas nitrified top ring the entire ring will be a light gray.
These instructions must be followed for maximum ring seal.
A torque plate must be used unless the bolt holes are not part of the cylinder.
The first stone is a 525 (220 grit) stone, done until there is .001 " left from final bore.
The bore must be round to .0002", checked 360 degrees from the bottom to the top of the bore.
Then switch to a 625 (280 grit) stone, 50% load until .0002" is left from final bore.
Then use the 625 stone at 20% load to final bore size.
DUCTILE MOLY RINGS
To identify a moly top ring look for a silver-grey plated finish with black phosphated top and bottom surfaces.
If there is a dot on the flat side of the ring, make sure it faces up.
Rough hone cylinders to within .003", intermediate hone to within .0005" with 220 grit and final hone with a 400 grit and a 10 to 12 RA finish with a 20° to 22° crosshatch.
CHROME RINGS
To identify a chrome top ring the face will have chrome plating, the top and bottom of the ring will be a reddish-brown.
Chrome on any of the rings is not advisable with nikasil bores.
These instructions must be followed for maximum ring seal.
A torque plate must be used unless the bolt holes are not part of the cylinder.
The first stone is a 525 (220 grit) stone, honed until there is .001" left from final bore.
The bore must be round to .0002", checked 360 degrees from the bottom to the top of the bore.
Continue with a 525 (220 grit) stone, 50% load until .0002" is left from final bore.
Then use the 525 stone at 20% load to final bore size.
ALL RINGS
The honing must be done slow to minimize heat build-up. No hand honing.
Final bore needs to be less than plus or minus .0002" out of round, checked 360 degrees around the bore from the bottom to the top of the cylinder.
This should be checked with a dial bore gauge.
The expertise of your machine shop is critical to the proper finish on your block bore.
When you receive the block back from the machine shop it will appear clean, the block still needs to be cleaned.
There could be material trapped in the honing grooves of the block that are not visible.
Failure to clean the block could lead to premature ring wear and blow-by.