OK, not trying to get a debate started on whether you should use a smaller or larger second ring end gap compared to the top ring. Some feedback on end gaps toward the large end of the spectrum and possible changes to oil control are the question.

The insert that came with my Mahle Powerpack forged pistons has end gap specs that are .024" top and .028" second ring end gap for nitrous applications. For forced induction it goes up to something like .028" top and .032" second ring end gap. I think it was .018" and .022" for normally aspirated engines without power adders.

For reference, the specs in my GM service manual are .010"-.020" top ring gap and .018-.026" lower ring end gap with a service limit ( means worn out I suppose) of .035" for both.

You never know what you might want to do later. Wondering if opening up the ring gaps into these larger gap ranges to "future proof" them for later mods is likely to affect your oil control negatively, especially as you rack up some miles on the engine. The Mahle spec for second ring end gap for a blower motor is right there at the GM service limit. We all know the GM service limit isn't setup for high output engines but seems like it would mean something?

Later, Michael

 

Found this:

http://kb-silvolite.com/article.php?action=read&A_id=

 

How much control do the top rings have over oil anyway?

 

none,top rings r to prevent blowby

 

I have Mahle pistons and used 22 top and 26 second and have no blowby and no detectable oil consumption. I was at first thinking about going with intermediate gaps cause I have about 10# boost and only get into boost once in a while, but I went with their blower gap recommendation and it seems fine. Looks like it was the right call. I also used the Quickseat and did a hard breakin.

 

If ya don't open um up with that blower will butt them and there go your pistons.It will tear the top land off of the piston.
DO NOT look at the GM manual. Its for stockers-- don't think yours will qualify.
Larger ring gaps will not kill ya when/if ya go N/A.
Now ya have to decide how much boost ya gonna run to get the gap on the low side of the limit.

 

I believe all that head porting got to his OWN head!