Recently when I set out to determine the gap for my new shortblock ***'y, I came up with some differences in the second ring gap between the piston mfg. (JE/SRP) and the ring mfg. (Total Seal) Now I know the default position is to always go w/ the piston maker's recommendation but I was curious as to why they were recommending .020" for the 2nd ring whereas Total Seal recommends .014" which is about what I'd have expected. These are forged pistons BTW in +.030" size. Anyhow, I just had to know so I called JE's tech line. The gentleman I talked to was very informative and I did not feel rushed. Some tech depts. are better than others as anyone who's called a few knows. He explained that the wider gap that's now recommended on the second ring is for two reasons. The first is to reduce pressure between the top and middle rings and the second (and I guess this is related to the first) is to reduce the resulting ring 'flutter'. The 'exact' recommendations he gave me were .0185" top and .0205" second ring as minimums. This is what I went with. I thought I'd pass this along for thought and/or discussion.

 

.014 is the min for most any ring gap
if you go closer than that the ring expands when hot and the two ends will but against each other when the gap becomes .000 That forces the ring to become bigger than the bore and will make the weaker aluminum ring land crack. So they must of had a problems with the smaller gap and are reccomending a wider gap. Not sure what makes their pistons different than others.

Are there and gas ports in them?

Ussually the second ring can be tighter because it is further away from the heat source so it expands the least.

Sounds like they also want more oil on the bottom of the top ring for lube. Maybe the silicone content is lower or something like that.

You can tell when you get to close upon dissasembly. The ring ends you ground for the qap will become shiny like they were polished from being so close. The file marks will be gone. Thats if they didn't break. We got down to .010 in some of the circle track motors. But they were rubbing and probably slowing it down.

I use .014 top with my Manley forged flat top pistons and never had a problem. Remember the wider the gap the more blow by and less compression o.18 is getting pretty wide. You may have to change them sooner. They will wear around .002 in the first 500 miles. After .024 they will show signs of smoke from the oil getting by.

One trick you can use is to replace the second ring with Total Seal rings. They have absolutely no blow by as there is virtually no gap at all because it overlaps itself. They also have less friction to. But if that piston needs the oil it may not be reccomended.

http://www.totalseal.com/

These rings will ensure the oil won't get past the second ring into the combustion chamber.

They worked for me on the street in every day driving.
The motor has a great compression pressure and the combustion is amazing. It allows me to run a 528 lift roller cam on the street.

leak down is near zero.
Still after all those miles.

Not sure if they still use them on the second ring or not.
at one time they put them on the top ring land but I think there was problems with carbon build up making the two piece design stick.

The best part is i get up to 30 mpg on the highway. Around town it gets only 14 and 10 if i drive it hard.

 

Geeze, this sounds like one of my old posts now in the archives which you actually took part in. I think it best to follow the piston manufactures specifications for the type of piston used. Then as you'll see I erred on the big side a bit.

http://forums.corvetteforum.com/show....php?t=1086186

 

I remembered it well once I read through it, good thread. And w/o a compelling reason to do otherwise, I also go w/ the piston maker's spec. But that's why I was so surprised. .018" top and .014" 2nd (or thereabouts) is pretty standard in street/strip applications so I wondered why they were recommending otherwise. He stated that the closer 2nd ring gap was now "old school" in his words, and then explained why, per the reasons I stated above.

 

I'm actually very glad to tead this I have 12.8 forged SRPs & new sealed power moly rings to install this weekend thanks, saved me a tech call & feel better about the rings

 

I'm glad to hear it benefitted someone else.