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Engine – 94mm CP Pistons

CP Pistons Cylinder Honing Recommendations For CPN & CPN2 For use with our CPN and CPN2. piston rings, we recommend plateau honing with a cylinder bore cross hatch angle of 35-40 degrees.

To reach this roughness, the manufacturers of honing machines and accessories recommend using for a gray cast iron engine block and Nikasil cylinders.

  • Conventional stones #220 - #280 grit
  • Diamond stones #325 - #550 grit

After honing with either the conventional or diamond stone, the same manufacturers suggest to finish your honing by smoothing the surface with a fine grit conventional abrasive (#400 - #600 grit) or to sweep the bores with a flexible brush or a nylon bristle plateau honing tool. This is necessary to get rid of jagged peaks and folded or torn material.

NOTE: Be sure to confirm with your honing equipment manufacturer that the recommended stone grit will produce the following Rz and Ra roughness recommendations.

Rz = 59 - 138 μ in [=1.5 – 3.5 μm]
Ra=15- 35μin [=0.4–0.9μm]

CP Piston Ring Recommendations:

Failure to check ring gap can result in severe engine failure. The following end gap recommendations are general guide- lines. 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.

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 81mm – to find top ring end gap for a street application.
(3.189 x .005)= .016”

Ring Specifications:

The following are guidelines for ring installation. Certain applications may require different clearances. Consult the enclosed charts and diagrams before installing rings.

Ring Gap Measuring Procedures

  1. A torque plate should be installed on engine (if applicable) and torqued to specifications.
  2. Piston ring should be below and square to the deck. (Figure 1)
  3. Measure ring gap with a feeler gauge or equivalent PISTONS Ring Gap Measuring Procedures measuring device. (Figure 2)

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 gap filing tool.
  2. Ring gap should be file in an inward direction and 1. If the ring has a dot or writing on it, install with this side up. 2. If the ring is a taper hook groove style, the groove square to the sides.

Ring sets are manufactured to fit specific bores. For every .001” over the intended bore size, ring gap will increase by .00314”.

Top Ring:

  1. If the ring has a dot or writing on it, install with this side up.
  2. Unmarked rings with inner bevel are installed bevel side up.
  3. Rings without dot, writing or bevel install either side up.

Second Ring:

  1. If the ring has a dot or writing on it, install with this side up.
  2. If the ring is a taper hook groove style, the groove always goes down. (Figure 4).
  3. Unmarked rings with an inner bevel install bevel side down. (Figure 5).
  4. Rings without a dot or inner bevel install either side up.

Oil Ring:

  1. Most CP oil rings are three piece – two rails and an expander.
  2. End gaps on rails should not be less than .015” and should not overlap.
  3. Do not modify expander in any way.


Due to the nature of high performance applications, CP Pistons/Pankl products are sold without any warranty of merchantability or fitness or purpose, express or implied. It is expressly understood and agreed between CP Pistons/Pankl and purchasers that as part of the bargain between CP Pistons/Pankl and purchasers, consideration of doing business with each other, all purchasers take, select, and purchase said products and services from CP Pistons/Pankl “as is” and “with all faults” and CP Pistons/Pankl shall provide purchaser with a full and complete opportunity to examine parts, inventory or services when purchasing from CP Pistons/Pankl. CP Pistons/Pankl shall not under any circum- stances, be liable for any special, incidental, or consequential damages, including, but not limited to, damages or loss of other property of equipment, loss of profits or revenue, cost of purchased or replacement goods, or claims of cus- tomers of the purchaser which may arise and/or result from the sales, installation or use of these parts.