iim not suprised the compression reading was down,he claimed he put a new,unseated ring in a cylinder that has who knows how much run time it has,of course the already seated ring will show better numbers.it is a proven fact that total seal 0 gap top ring seals way better than a standard ring,but to each there own.

Looks like he actually was talking about running a gapless second ring. So kind of moot of me even posting it.

While a gapless ring will give very good leakdown numbers, and if I saw 15% leakdown using gapless, then Id be alarmed. 15% on a convential ring with a few hundred hours, Id think that's normal.

As we know theres more to how the ring actually seals when running then when doing a leakdown test. Just because one engine leaks down at 3% with gapless, and the other at 13% using convential rings, I'd be owing someone some cash if that identical engine made 10% more HP on a dyno. Heck, why would anyone, even the automakers run anything other than gapless when in the quest for MPG, power, and meeting EPA regulations. The cost isn't that drastic between them.

Ive seen several buddies running gapless rings. And after several miles of wot running, still have a little bit of oil mist from the breathers, just like the conventional rings.

I think we need to call robby. Id be in for some total seals if I can pick up 80HP.

i think it was patrick swazey in road house when he said OPINIONS vary,interesting reading..

joe,as far as the big 3 not useing gapless top rings,i think from a cost standpoint,at app 125 bucks a car,and millions of cars produced,well,you do the math,with the materials and coatings on todays rings,a production engine just does not need them,imo.i put them in my 588s in the fountain,and in joes engines,i think it is money well spent in a supercharged,or high compression engine.dont get me wrong,im not saying conventional rings are bad,just not as good as the gapless top ring sets.

maybe eddie young will chime in,id love to get his take on this.

Im not disagreeing with ya. My response was more towards strippoker's. He mentioned his leakdown numbers, and how little blowby he had, and he had conventional rings with whipples, which served him well. He mentioned how the leakdown results using gapless rings can be misleading.

I think what he was getting at, is gapless will always show better leakdown numbers. But, doesn't necessarily mean the cylinder is sealing 10% better when running than a non gapless setup. Leakdown % is simply a measure of what air is lost when doing a static diagnostic test. It doesn't tell the entire story of whats going on inside the engine at 6000RPM with say a 300 shot of nitrous , or 10-15lbs of boost. Theres way more to a good cylinder seal than what a leakdown tester will tell you, on a cold cylinder, with no combustion pressure, etc. Now, a blowby tester/meter, will give a better idea of how things are sealing up when the engine is in real world operating conditions.

Gas porting designs, ring flutter, standard tension, low tension, vaccum pumps, pressure differentials above and below the ring, thermal expansion, and so on come into play. A standard ring needs combustion pressure on the top side of the ring to aid in sealing. We have a set ring gap to follow, to allow for thermal expansion when running when using a conventional ring. It does not have any of this going on during a leakdown test.

But, with that being said, I would absolutely agree to have used the gapless top ring in your build, joes build, and even in my engines. I am fine with the old fashioned speed pro plasma moly rings, mainly because they just work for your typical low boost low hp marine engine like I have. Been around for ever. But, to the original poster who has a 454 420HP, its not needed, and if he sees 12-15% leakage, or even a little more, leaking past his rings with a few hundred hours, and the valves are sealing well, I would tell him to run it. Just my opinion.


Would also love to hear some insight from Eddie or one of the other pro's. I think we'll find that it boils down to personal preference. While gapless rings are great, theres still a million builders using non gapless with good results. Whether it be a 500HP engine or 2000HP engine. A 400 dollar set of rings with a improper honing/finishing process is no better than a 80 dollar set of rings.

I agree with Onoxus. For the average hobbyist a leakdown test should be used like a compression test, to check for consistency, and listen to where the air is getting out. There are many variables as Mild mentioned above. Another huge variable is the test equipment, and how the test is performed. A leak down tester is a differential gauge. There is a specific control orifice in the middle that I believe is supposed to be .040". If you change the "set" pressure by a few pounds, or the cheap, mass produced orifice is actually .038", or .042", it will change the leak percentage readings. So it's hard to compare numbers from one engine to another. If you know what your gauge reads on your engine and test regularly using the same procedure every time, you'll be able to easily spot any decline in sealing.

As far as the ring debate... As I have posted in the past, I strongly believe running a gapless second ring, especially in a blown marine app, is a bad idea. Gapless top rings work great in certain applications, and a properly gapped conventional ring works great also. There are many variables here as well.
* This is not a bash: Eddie is the only builder I know that uses gapless second rings, and seems to have excellent results. Maybe he can chime in on why, and how he makes these work.

is i have a guy doing my motor work seance i am new to the bigger motors and just got the new to me boat this year. now he called me today to let me know about the the leak down and compreshion tests. port leak down where at mostly at 10% with a few around 20% and the compreshion test where all in good range. now on the starboard motor is where it gets weird. when i would start it there was alway a strong smell of raw full, then a few months in of me running the boat i started to notes that after going out the starboard motor oil presher would be down around 20psi from the port. now he sad that the leak down was the same as the port with most in the 10% range with a few around the 20 mark. now with the compreshion test all where good but one. one was at 5.....yes 5 psi now i heard some stuff he sad it might be but he sed he need to get the valve cover off and do some more tests. just wondering what u all would be thinking about my big OH NO

i cant see how 1 cylinder could have 5 lbs on compression test but a max of 20% leakage on that cylinder,it does not add up,that cylinder should be near 100% cyl leakage.

Listen to where its coming from like I was saying earlier,,,,,intake ,,,,exhaust,,,,will indicate one valve or the other,,,,, 5 PSI is a big problem and should be easy to find. Years ago I had a keeper pop off and held a valve open and the motor still made 50 psi !!!

know anyone with a scope you can stick in the spark plug hole ???