From most of the engine buildup articles I've read in recent years it seems most people are using a larger second ring gap than the top. GM has also went to this with the newer motors like the LS6 from what I hear. And I seen some test data from I believe Speed Pro? that showed more power was gained going with a larger second ring gap mostly above 7000 rpm. One magazine story tested ring gaps and also total seal type rings and found more power as the gap decreased untill the ring ends butted. The theory behind the larger second ring gap is that if the pressure between the two rings exceeds the pressure above and behind the top ring then the top ring will unseat itself and lose ringseal. The large second ring gap vents the pressure between the two rings to keep the top ring sealed and the venting of the pressure between the two rings also helps to keep the amount of oil down on the oil control rings. All of this makes sense and I've assembled two smallblocks this way, one using .016 top and .018 second ring gap, and the other with .018 top and .020 second ring gap. Both engines run excellent but do seem to contaminate/darken the motor oil faster than normal. Neither engine has any noticeable blowby and show excellent cranking compression. Today I read an article in October Hot Rod magazine about an engine combo that Dick Landy builds, it's a 500hp mopar 360 with a 4.030 bore and 7400rpm redline. He sets his gaps at .014 top and .008 second and says; it's something we've done for awhile now that works for this bore size. In my Smokey Yunick book, Smokey recomends .003 per inch of bore, that's only .012.
The last engine I assembled was my Son's 331 and we set the gaps at .014 top and .012 second, one of my old GM service manuals recomended .012-.013 for the top ring. The engine has been fired on a test stand but hasn't been put in his car yet.
So what's the deal here? Run a wider second ring gap if it's going to be spun over 7000 and you don't mind changing oil more often? Is there more power with more or less gap? If both gaps were set the same I would think the top gap would close more due to more heat exposure thereby making the second ring gap larger to vent off the unwanted pressure between the two.
????????????????? :confused: Bob

might just be a typo?

when i bought the speedpro rings
they said they found more performance running a larger 2nd ring gap
searching this forum says that a larger 2nd ring help the top ring seal... or something like that
also explains why the totalseal dont work well in a real situation except cranking pressure.... or something like that
the topring floats or something like that...

Motor Martyr might just be a typo? No, I'm sure it wasn't a typo. Page 118 in October issue of Hot Rod. It looks like they've done a lot of research on rings for the Landy engine. They also do a trick backcut on the top ring groove to apply more pressure against the back of the top ring. The article also quotes Landy with saying: Tight Ring Gaps work good for no blow-by.

So, are the oldschool thoughts of tightening the gaps as much as possible right?

The best top ring gap setting for power is to have the ring gaps as small as possible, without letting the ends butt together. This gives the best combustion seal, which is one of the most important elements in producing horsepower. The actual ring end-gap is influenced by many variables, such as: Basic ring material - ductile iron will expand at different rates than grey iron and steel. Piston material - some alloys will absorb heat rather than transferring it. (One of the functions of rings is to transfer combustion heat to the cylinder walls, and thus to the cooling system). Location of the top ring in relation to the piston crown. Top groove rings located closer to the piston crown will be subject to greater temperature than a ring that is further down. And the list goes on, type of fuel used, fuel mixture, cooling system efficiency, etc., etc.
Now, since the best combustion seal is the ultimate goal, it was the theory in years past that the second ring gap should be tight to help trap the combustion gasses that have gotten past the top ring. In many cases the second ring gap was significanty tighter than the top ring gap and this was easily accomplished because there is much less heat encountered by the second ring, therefore it will not expand as much as the top ring. This was (is?) the theory behind gapless rings.
But. . . it has been found that the combustion force that gets past the top ring was being trapped between top and second ring, thus lifting the top ring off of the piston's side groove and allowing even more combustion pressure to be lost. The thing to note here is the ring seal to the piston groove, not to the cylinder wall. The ability of the ring to seal on the ring grooves is just as important as the seal between ring face and cylinder wall. We can influence the ring face seal with such tricks as gas ports, etc., but if groove seal is lost then the ring will not seal effectively. Therefore, modern engine building theory says to open up the gap on the second ring, slightly more than the top ring.
Remember too, that the second ring serves two functions: 80% compression seal and 20% oil control.

It sure would be nice to see some more detailed conclusive testing on this. If the top ring is set say at .012 and is very close to perfect (almost butting at running temperature) and the second gap is set at .014 and is subjected to at most 50% of the heat compared to the top ring then the difference in gaps at running temp could be around .008? I wonder what the ideal difference in ring gaps between the top and second should actually be?

There again, the "ideal" difference in ring gaps is very dependant upon the ring design and materials. Most purpose-built, naturally aspirated drag race engines use some sort of premium-material top ring, such as steel or high density ductile iron like F-M's Hellfire or Clevite's FirePower rings. A back-cut (reduced radial wall) .043" ring will act much differently than a 1/16" D-wall design, as far as heat expansion is concerned.
Most high performance second rings are cast grey iron, which is considerably less dense than steel or ductile iron. For this reason, back-cutting the second rings will cause even greater expansion range, even though the ring is subject to less combustion heat and is closer to the oil film on the cylinder wall.
You will find that most professional engine builders will close up the gaps to a point that they feel is too close, run the engine on the dyno and check for end-butting. Then build a same combination engine with very slightly larger gap, until the butting goes away. This consumes a lot of time, money and resources but is necessary to build drag engines capable of running on the ragged edge.