Learning how to gap and stagger piston rings is an essential part of engine building that ensures your motor runs efficiently. If you fail to do this correctly, you will experience blowby, which occurs when combustion forces gases into the crank case and causes oil to blow out the valve covers. By carefully measuring the gap and positioning the rings properly, you can prevent this issue entirely. This process requires patience, but will result in a pretty nice little motor.
Measuring The Initial Gap
To begin, you must determine the initial size of your ring gap before making any adjustments. Install the ring in the bore with the dot up. Once the ring is in place, square it up inside the cylinder. You can then use a feeler gauge to find the exact initial measurement of this gap.
Filing And Calculating Piston Ring Gaps
Now put the ring into the ring filer to make your adjustments. You must make sure that the filing direction is toward the inside of the ring. Take a little material off the ring, reinstall it in the cylinder, and check the gap. Continue this repetitive process until you get it right.
But what is right for your engine? If you are building a street motor, you just multiply the bore size by 0.0045 for the top ring. In this specific case, that calculation came up to 18,000. Next, you multiply the bore size by 0.35 for the second ring, which equals 14,000 in this case. Finally, the oil ring should have a gap that is a minimum of 15,000.
For the final step of gapping, take an oil-soaked stone and just knock the edges off the ring opening. Doing this prevents any scarring of the cylinder during engine operation. If you are building a nitrous or blower motor, you should consult a ring gap chart. These charts cover just about every combination imaginable.
Staggering The Ring Gaps
Next, put some oil in the grooves. You can then install the rings and stagger them to prevent blowby. Place the oil ring spacer gap between the 90-degree arc labeled A. Then, position the oil ring rail gaps at the spots marked B.
After placing those gaps, turn your attention to the compression rings. Address the remaining compression rings one by one. You must rotate the lower compression ring gap to the C position. Place the top compression ring gap at the D position to complete the staggering process.
Following these simple steps for gapping and ring staggering will prevent future blowby. It keeps oil where it belongs. Once your rings are properly filed and positioned, you can proceed with confidence knowing you are going to have a pretty nice little motor.
