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Discussion Starter · #1 ·
ok so i decided to try gapless rings on my son's engine. any secret to install them? bbc 468
 

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is there a problem with running them?

GM thrashed some engines back in the late 80's to early 90's as emissisons stds were changing. One area of problem was top ring location. The area between the piston, the cylinder and the top ring would trap gases that would go unburnt. On the exhaust stroke this was expelled and more pollution was put into the air. If GM could reduce this area they could reduce the amount of unburnt carbon emmissons.

Ring packages were experiment with and ring sizes. If GM could use a thinner ring they could keep it higher on the piston and reduce the area of unburnt gases. The negative was the thinner ring would flutter in the bore loosing seal. The fix was to open the second ring gap up larger then the top ring. This allowed the trapped gas between the 1st and 2nd ring to exit without causing the pressure area between the 2 that caused the top to flutter.

Now once this was done new found HP was a side effect. This info was then given to the boys in Mooreville, NC who then for years opened 2 ring gaps up while the rest of us kept them smaller. In and around 2000 piston companies finally started to change instructions to inform engine builders to open the 2nd ring up as the norm.


The above is the abreviated version but to you Slot I would say if you have the gapless and you want to try them then by all means they do work and will run just fine. From a performance outlook and as someone who supplies engine builders and individuals with tech and parts. . .I don't recommend them.
 

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Sealpower did a test on leakdown VS Horsepower. Thats why they don't sell them. If you use the older 2nd ring type, they trap any top ring blowby between the top and 2 nd ring and that tends to unseat the top ring on the next upstroke. Current thinking is to open the 2nd ring gap up larger than the top ring to prevent this. kinda shoots the gapless 2nd ring idea to hell.... We have tried them thru the years and have found polished bands on the cylinder walls that show ring flutter. We don't use them. The newer design is a gapless top ring, heat and detonation are their enemy. The blown/alcohol guys use the gapless 2nd ring to keep the excess fuel out of the crankcase to help prevent fuel dilution in the oil. Alcohol makes a poor lubricant. If you are gonna use these things anyway, have the block honed with a torque plate, with a multi-step plateau finish and convince yourself that you made the right choice. Just don't admit the gapless use to the engine builders, its pretty easy to see their opinions. P.S. tried the Z-gap, gapless deal too, those just wear the overlapping ends of the rings off, and quickly. P.S. I have several friends that work there,(they are local to us), we just don't discuss rings. TIMINATOR
 

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Discussion Starter · #12 ·
wow, wish i knew this before i bought them. the machine shop that did the machine work say's he use's them all the time. i am going to call and see if i can return them.
 

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chris what i did not read is the ring set in question a second ring gapless or some of the newer top ring gapless ? I have heard top ring setup may be alot better.
also at what rpm would ring flutter set in?

I run a set of the childs/albert 2nd rings on a pair of 496's in a non race app. cant say there is or isn't any performance gain from the molys i ran before (seat of the pants) but there was a big difference in blowby out the valvecovers, zero gapped made the engines dry.motors only run 6000-6500 depending on the props so maybe i not turning them up anough to get into flutter. my valvecovers are just some m/t style with 3 inch stands filled with course brillo pads to stop raw oil from coming out.no puke tank
 

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wow, wish i knew this before i bought them. the machine shop that did the machine work say's he use's them all the time. i am going to call and see if i can return them.
I've got customers that use them and have good luck with them. . gapless stuff. It's just that GM spent millions and found the best way and now it is becoming the accepted norm.
 

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chris what i did not read is the ring set in question a second ring gapless or some of the newer top ring gapless ? I have heard top ring setup may be alot better.
also at what rpm would ring flutter set in?

I run a set of the childs/albert 2nd rings on a pair of 496's in a non race app. cant say there is or isn't any performance gain from the molys i ran before (seat of the pants) but there was a big difference in blowby out the valvecovers, zero gapped made the engines dry.motors only run 6000-6500 depending on the props so maybe i not turning them up anough to get into flutter. my valvecovers are just some m/t style with 3 inch stands filled with course brillo pads to stop raw oil from coming out.no puke tank
On the top gapless I have been told it depends on the piston mfg and how good the ring lands are when it comes to being machined. Warp may have some stuff he can share as I am willing to bet he has thrown these on an engine for testing.

Flutter rpm will vary depending on piston speed. . . ie the stroke in the engine. So it will vary.

You'll get good leak numbers and hell I sell leak down testers. My question is what is the leakdown of the engine when it is running in its powerband. I've never gotten an answer on that question.

I maybe mistaken but I think Mercury marine states on a BBC that 30% leak down is acceptable. Merc may know what the leak down is at 5000 rpm.
 

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Discussion Starter · #18 ·
back to the top. ok i am using total seal T20960 rings. gapless 2nd ring. ok do i file fit the other rings? this is a yes or no question only. i have never used these before and have no clue.:)sphss
 

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back to the top. ok i am using total seal T20960 rings. gapless 2nd ring. ok do i file fit the other rings? this is a yes or no question only. i have never used these before and have no clue.:)sphss
The end gaps need to be set, like any other ring. The main difference is you have to do both ends of the gapless ring.
 
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