Well, let's see... as I see it it's kind of an apples and oranges thing. Speed Pro workes with the racing community to develop and engineer piston rings that meet certain requirements. Where the OEM is looking to maximize fuel economy, minimize hydrocarbon emissions etc.. Those aren't necessarily the primary goal of a high performance racing engine. Don't hear many race engine builders gabbing about the reduction of hydrocarbon emissions... at least not the ones I've met.

The funny thing is, I have a new SDPC 2002 catalog and on page 44 there's a Speed Pro "Tech-tip" which lists the recommended ring end gap. Here's the list:

Top Ring
Moderate Performance......................... (.004 x bore)
Drag race/oval track............................. (.0045 x bore)
Nitrous (street)..................................... (.006 x bore)
Nitrous (drag)........................................ (.008 x bore)
Supercharged...................................... .. (.006 x bore)

2nd Ring
Moderate P............................................. (.003 x bore)
Drag and oval......................................... (.0035 x bore)
Nitrous (street)....................................... (.005 x bore)
Nitrous (drag).......................................... (.0065 x bore)
Supercharged...................................... .... (.005 x bore)

So, maybe there's some miscommunication somewhere along the line. SDPC is not totally ignorant when it comes to engines, those guys build quite a few themselves and it seems that the "new spec" would be something they'd feel most confident in putting to print in their new catalog but they don't. I don't really know what that says and I'm not trying to insinuate anything but I just find it strange. I've also found some info across the net on the new recommendation with regards to the 2nd ring gap. Most of the stuff is about 2 years old so who knows.

Back to the oem and the "cutting edge".... I am not aware of anything like the new Speed Pro Hellfire ring used in any oem applications and from a racer's standpoint... that ring looks to be pretty cutting edge. So what does that say? Again we're talking apples and oranges... maybe it's not a good oem design but the ring was developed by Speed Pro with the help of Mike Moran and on a smaller part, Warren Johnson. It looks to be an excellent ring design for those guys running insane amounts of boost and/or extraordinary cylinder pressures. Lots of guys are swearing by the Hellfire rings right now. Then again... the oems don't use gas ports and hard titanium nitrate coated rings either so what does that say? Well, they build engines for different reasons. Go figure but I'd be willing to say that any resources at FM's disposal is also at the disposal of Speed Pro. Sorry, not buying that one.

-Mindgame

 

Well, to throw my 2 cents in here. I know many comp, ex-PS Truck, and PS engine builders who use larger 2nd gaps than top gaps. In fact, so many high rpm people are doing it these days, I thought it was pretty much understood. I guess I was wrong. Many NMCA and PRO category racers have been doing this also. I can't speak for the nitrous or supercharged group, but the N/A guys have been using larger 2nd ring gaps for more than 3 years.

I only heard of this about 2 years ago, actually from the current champion in PRO's Pro Stock class (head's up street racing). Anyway, my engine is set at 0.020" top and 0.026 2nd.

From what I can tell, larger 2nd ring gaps are most beneficial in high rpm applications using vacuum pumps, with crankcase vacuums over 10" Hg. In this type of application, I have seen actual dyno results of power increases with larger 2nd ring gaps.

Shane

 

Well, as you say, the OEs don't have a "hellfire" ring because they have no applications that need it. However, you're mistaken if you think that "any resources at FM's disposal" are also at the disposal of Speed Pro. The aftermarket side of most OE suppliers is a VERY small part of the profit those companies make. Resources are devoted in proportion to the profit a division makes. Guess what that means for aftermarket divisions? I'm not asking you to "buy" it, but it's very true. Again, I wouldn't be in Detroit if it wasn't. Because of this lack of resources in aftermarket engineering they do use racers as guinea pigs and "partners in development". The racers know this and welcome it most of the time, so it's not a disadvantage to either party. The OEs try not to use their customers as guinea pigs so by necessity their resources must be more extensive and their lead times longer. The design criteria for an OE is also more demanding than for a race engine, thus again dictating that more resources are needed. It's really that simple.

I'm not trying to insult aftermarket engineers here. Heck, I used to be one, and I know what they're up against. They are 2 totally different markets and thus demand different strategies to sell to them.

 

Interesting debate.... found another article where the head engineer at Wiseco doesn't agree with the bigger 2nd ring gap theory either. So much for the "everyone's doing it mantra".
I'm not disagreeing with the advice given here... it seems that there probably isn't any harm in running a larger gap. Been mentioned here more than a couple of times and when I asked a good local race engine builder about this today he said about the same thing.... "No harm but can't really justify any real gains unless you're turning the revs..... then the thing most likely needs gas ports anyways....".
I just think it's funny that what works and has worked for so many people for such a long time is now "wrong". Maybe it is... I'm not necessarily saying it isn't. The theory sounds good to me... then again I've always been more of a run-it-and-show-me kind of guy. Seen alot of theory, and it doesn't always win races.
As a matter of fact, I'm going to be following the bigger 2nd ring gap thing on my LT1 engine build just to show that an old fart like me can learn a new trick too.
As for this "everyone in the big leagues is doing it thing"... well I use to play in the big leagues and up until here a few years ago I had one of the quickest cars in my state (class-wise). So what the hell... the way we settle debates around here is simple... when you guys wanna line em up?

Chuck, what kinds of gaps are you guys running on your engines. I'd be curious to see what the more endurance oriented engine build guys are doing. No wishy washy, just the facts bro.

-Mindgame

 

I'm most interested in finding out how some of the racers out there determine what gap to use in their engines. There's not really a generic recommendation anyone can make for most engines. We end up having to refine them through testing and simulation to see what's going on in there. Almost no racers have access to simulation programs sophisticated enough and I bet that none of them instrument pistons to read land pressures during a combustion cycle. I assume a racer calls up a company like Speed Pro and asks them what they should run. The guy at Speed Pro gives it an educated guess, and that's the end of that. I'd love to see what testing data is behind Speed Pro's recommendations. Optimum ring gaps just can't be guessed at, but then again it's just like cam profiles, etc. The fastest racers may start with a recommendation from the aftermarket manufacturer, but then they test themselves to find out what REALLY works.

 

I am an old fart, I guess! This discussion has been interesting. I have followed the old fashioned .004-.006''/1" of bore "rule" for years. Guess there's more to it!

Rich Krause