P I STON R I NG END GAP GU I DEL I NES W I F. 0000 1 -A 06 - 04-202 1
NOTE: Piston ring end gap guidelines are for general information only. Always refer to the OEM service manual for critical engine data. When installation is not clear, contact your Wossner dealer or professional engine builder before proceeding.
Wossner performance piston rings are generally supplied as a “drop-in” to the recommended bore diameter, unless noted for file fit applications. Ring end gap is the result of the ring manufactured tolerances, as well as the final bore diameter and geometry of the cylinder. It is possible that the final ring end gap has variation due to all of these influences. It is important to inspect the piston ring end gap during installation, and make adjustment to the end gap if required.
Too little ring end gap can result in catastrophic engine damage! Always inspect ring end gap during the assembly process and correct this before final assembly.
As a general guideline, ring end gap that is larger than expected is less of an operational concern than too little end gap. Compression ring end gap that measures over spec by more than 30% over max, will have minimal impact on the operation and sealing of the compression ring. The condition of the cylinder, cylinder wall finish, piston ring groove, and ring interface are critical relationships to the function and sealing of the piston ring. Inspect the piston ring end gap in your cylinder, approximately 13mm (.500”) down from the top of the cylinder. Install one piston ring at a time, use the piston to assure the ring is flat and square to the cylinder bore. Ring gap can be measured using a feeler gage. The charts below illustrate some typical ring end gap dimensions, based on general guidelines. To calculate the ring end gap, multiply the cylinder bore diameter in inches X the end gap mentioned on the chart:
4 CYCLE PISTON RINGS
2 CYCLE PISTON RINGS
APPLICATION
TOP RING
2ND RING
OIL RAILS
APPLICATION
TOP RING
2ND RING
NATURAL ASPERATED
.0040
.0050
.015 MIN
NATURAL ASPERATED
.0040
.0040
NA RACING
.0045
.0055
.015 MIN
NA RACING
.0045
.0045
FORCED INDUCTION
.0055
.0065
.015 MIN
SNOW / MARINE
.0050
.0050
HEAVY LOAD / HIGH HEAT
.0060
.0070
.015 MIN
HEAVY LOAD / HIGH HEAT
.0055
.0055
The filed ring end gap must be properly aligned to the cylinder bore, and the ring ends remain parallel and even. All burrs or sharp edges must be removed to prevent damage to the ring groove and cylinder wall. Extreme care should be taken for all assembly steps, always work in a clean environment and use proper PPE when performing all operations. TERMS AND CONDITIONS: Due to the nature of high performance and racing applications, Wossner components are sold without express warranty or any implied warranty of merchantability or fitness for a specific purpose. Wossner shall not, under any circumstances, be liable for any specific, incidental or consequential damages, including, but not limited to, damage, or loss of property or equipment, loss of profits or revenue(s), cost of purchased or replacement goods, or claims of customers of the purpose, which may arise and/or shall result from sale, installation or use of these parts. Installation of these parts may void vehicle manufacturers warranty coverage and/or may cause the vehicle to be illegal in some countries. Please check with local laws on the road use of your vehicle. Wossner reserves the right to make product improvements and changes without incurring liability with respect to similar products previously manufactured. By using these parts you are accepting these terms and conditions.as it reaches operating temperature.
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