Modern Vespa

I have one ring with a 0.25 gap, and the other with a 0.28 gap. Both are a little over the recommended 0.23 for my 177. Is there a recommendation to put the tighter gap as the top or bottom ring, or does it not really matter?

Thought 1: Well, the smaller gap on the top will hold the pressure better.

Thought 2: but the top ring will see more expansion due to heat, so better to put the larger gap on top.

In the end, as long as there is enough clearance the difference is likely negligible.

top ring gets more heat and expands more. so common sense says put the larger gap on top. but people dont have common sense when it comes to ring seal. most assume ring seal is worse with big gaps and they would be wrong. ring gap is very important. ring seal comes from cylinder compression. ~1200psi. the gap provide path for that pressure to get behind ring and push out toward wall. so small ring gaps are potentially bad. when ring expands and the ends touch you score the cylinder instantly. in addition very small gaps (that dont touch) dont allow enough path for pressure to get behind ring. the second ring has longer path so its okay to make second ring gap bigger than top. I used to build my 4g63 motors with 24 top and 28 second when most built them at problematic 16-18 top and second range. the wrong assumption is thinking small gaps allow less pressure to escape past rings through the gaps. poor ring seal comes from not enough pressure around the entire circumference of the ring. of course good ring seal starts with round cylinders and no scoring. whole different conversation.

very high performance engines often drill top of pistons with holes that lead directly to back of top ring. for sealing very high cylinder pressures.

4 stroke engines have a third oil scraper ring. they do not rely on cylinder compression for seal. ring tension alone does the job to limit oil on wall.

Thanks for the answers guys. I'll put the larger gap on top.