crossbredfoxbody

What is proper piston ring gap with n20 I gapped mine at .030 and .060 on my 5.3 ls build any input would be appreciated

Jontall

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

KCS

iTrader: (20)

.030" and .060" for ring gap? How'd that run?

Brandon35thSS

not sure about an ls1 but old shcool sbc standard ring end gap is .004 per inch of bore.

ViaBellator

iTrader: (2)

The "minimum" ring gap is exactly that, but there are "optimum" gaps for different applications. Big boost and Big nitrous require the largest.

I went with .019-.020 on my 4.030 bore 408. N/A with the possibility of moderate boost later on.

That Wiseco link above is what I used when I built mine.

tom falco

DUDE those gaps are WAY OUT. Basically you should have .004 for every inch of bore. This is the old rule of thumb. The first ring should be around .016-.018 and the second should be .014-.016. This also depends on application. But why would you have a .030 on #1 and .060 on #2 ?????????? The top ring always has more gap than the second. Top ring runs HOTTER. Remember the gaps open up on the break in period and also 2k down the road. I have installed rings and ran gaps of 14 top 12 second. Then after a 2k tear down found the rings at 16 Top and 14 second. This is normal and is because of seat in. Those gaps you are running are beyond acceptable. That motor is going to leak down hard. With that said i have done experments with wide gaps as high as .030 with little effect. But .060 thats way to much. Good luck TOM

helicoil

iTrader: (104)

For about the last 15 years, at least, OE manufacturers have run a 'wider' second ring gap in comparison to the top. This is also common place in a race/performance based engine. For example. 4.00" bore = .018" Top and .022" Second (no power adder).

Speed Pro/Sealed Power tested this years ago and realized there was power to be gained in the higher RPM's with a wider ring gap on the Second ring which allowed pressure to escape that was trapped in the second ring land area that would otherwise cause the top ring to flutter and 'unseat' and leak even worse, costing HP.

So a wider gap on the Second actually allows the Top ring to stay seated throughout the entire power stroke because it allows a leak path to the crankcase, yep, the crankcase. Wouldn't that be blow-by you might be thinking, well sort of, but it really is a very small amount, but just enough to be effective. Bottom line it works! Good engine builders do it, the OE's do it, and the ring manufacturers recommend it, just read the instructions.

I should add that .030" gap on the Top and .060" on the Second is ludicrous!

tom falco

That is why you use thinner rings on performance engines. Honda is experimenting with closer second rings and finds that it works better than wider gaps with their thinner metric rings. There is a load of different thoughts on this subject. Basically the gap is important because most of the ring is inside the land. But with the high preasures inside the cylinder a bigger gap leaks like crazy. I did several dyno tests on ring gaps years ago and found that gaps did make a big difference at high RPM'S. Ring flutter is best controlled with ring thickness. I do GT3 porsches and follow the factory gap procedures and the second ring is always gapped the same. I have read what you are saying and it does make sense on a performance driven engine. On a high spinning engine thinner is better and that is why HP pistons run thinner rings. When we do strokers with one ring the motors really dont last and have a tendency to smoke a bit. (the second ring also controls oil burning)So does the second ring gap need to be wider???? It depends who you talk to and how the top ring seals. Years ago we used to drill the upper ring land with tiny holes to preasurize the top ring into the walls. This is an old trick . Now a days that is really not necessary. I have never seen a difference on dyno humbers between lets say a Top gap of 12-14 and a Second gap of 12-14 Once again the preasure between the top and second ring is determined by the gas preasure behind the ring. Porsche claims that the top ring presurizes the second and with to much gap it does not seal properly. As far as .060 what is that all about. A top at .030 is wide but not as outrageyous if the motor is preasurized .. There is a big difference in gaps and HP on the top ring. We tested different gaps and the dyno numbers made quiet a difference in HP with gaps over 16 top. Believe it or not total seal gapless makes the most HP and does not seem to have flutter because of the second ring gap being close. Also the second ring is normally a softer ring and has a tendency to open up wider than the top after break in. Ring gaps are like sox everyone weare them but they come in all different COLORS Peace TOM

PS very good point and well taken. WE have been discussing this theory in the shop for some time now and it does make sense on a racing engine. The oem guys are also widening gaps as you so rightly point out. We cant figure that out because of the PFPM lower ratios of moders trannys and final drive ratios. Good post heli coil.