piston oil ring gap

[cinquecento]

There is lots of advice on gapping compression rings.. but very little on ensuring oil ring gaps are sufficient.

The issue as I understand it is.... upper and lower oil ring gap is affected by the tension supplied by the oil expander ring..(and these need to be installed onto the piston and then the piston installed into the bore) before an accurate measurement can be taken..which is kind of hard as the rings is not really exposed to measure.

I understand piston drag with the oil rings installed can be measured with luggage scales (did this and I need 6kgs to move a piston). This is abt right for a 2.8mm ring set..but doesn't help with a gap measurement.

Manufacturer recommends 0.015"..however when I place a single ring in the bore and messure the gap (as per the top two compression rings), the ring is a loose fit with only 0.006" gap.

How can I measure the gap with the correct tension?

Thanks in advance..

[Boosted LS1]

Fit the ring into the bore and level it with a piston crown and measure the gap. If the gaps to small you can fille the ring ends which will increase the gap. After filing then debur any sharp corners.

[cinquecento]

Thanks Mike..

So it's just following the standard process for gapping piston rings.I had discounted this as the oil control rings are quite loose in the bore..yet seem to provide sufficient tension once installed on the expander.

I appreciate your help....Lindsay

[PaulKemp]

Oil rings do not usually need gapping as they have 3 separate pieces, and are not constrained by the piston ring lands.
The 2 compression rings do need gapping to manufacturers tolerance and are done before putting them on the pistons.
There are YouTube videos that will show you what to do.