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 Post subject: ring end gap
 Post Posted: Thu Feb 17, 2011 12:55 pm 
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i am just about to gap rings for a sbc 408,, bore size is 4,165,, this is mainly a street car but bit has nitrous on it, nitrous would be maximum 300-350hp,, was going to gap them at 22 top,,25 middle,, but started researching it and now am confused.. what would be a safe ring gap for a mainly streetdriven sbc


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 Post subject: Re: ring end gap
 Post Posted: Thu Feb 17, 2011 6:34 pm 
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zephyrc wrote:
i am just about to gap rings for a sbc 408,, bore size is 4,165,, this is mainly a street car but bit has nitrous on it, nitrous would be maximum 300-350hp,, was going to gap them at 22 top,,25 middle,, but started researching it and now am confused.. what would be a safe ring gap for a mainly streetdriven sbc


For N/A only I'd set the top a little tighter than that at .018 and the 2nd at .026. When you start spraying then it needs a little more on the top. I would think the .022 should be enough for that app since I've sprayed 200 on an engine that was gapped at .016 (smaller bore - 4.030).

I think your .022 and .025 would be fine and safe. The 2nd gap is "safe" to much tighter than the 1st , but you don't want it tighter.

Curious what your research found?

Rick


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 Post subject: Re: ring end gap
 Post Posted: Thu Feb 17, 2011 7:36 pm 
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I agree with Rick, the .022 and .025 would be safe...I am looking at the paperwork with my new hellfire rings and they recommend for "street moderate turbo/nitrous" the top be bore x .005 and the second be bore x .0055


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 Post subject: Re: ring end gap
 Post Posted: Sun Feb 20, 2011 4:27 pm 
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i got various reccomendations from27 thou to 30 thou for the top ring...i have gone with 26 thou top and 28 thou second ring.. what is moderate nitrous use ,, is it 150hp or 250hp or 350hp.. i figured moderate meant up to 200hp and 350hp would be described as heavy nitrous use.. so i gapped the rings for heavy nitrous use.. thanks for the help


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 Post subject: Re: ring end gap
 Post Posted: Sun Feb 20, 2011 5:27 pm 
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You need to pay close attention to the SECOND ring end gap!!!! Too little there can cause the top ring to unload, or "flutter" as it was referred to years ago. That second rings' main function is oil control so anything that comes by the top rings has to go into the pan, not get caught up in the second ring and cause top ring problems!! .002 probably ISN'T enough, IMHO!

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 Post subject: Re: ring end gap
 Post Posted: Mon Feb 28, 2011 9:55 am 
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i called JE about my ring gaps(they sold me the rings) and they told me to go with .029 top and second ???

In the paperwork with the rings it says for "nitrous race only", top is bore x .007 and the second is bore x .0065 but they are telling me to do both rings to the bore x .007

We are planning to use 200 hp at the hit and add 200-400 hp more to get the numbers we are looking for


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 Post subject: Re: ring end gap
 Post Posted: Mon Feb 28, 2011 12:21 pm 
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Ken, what's a "flutte"? =;


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 Post subject: Re: ring end gap
 Post Posted: Mon Feb 28, 2011 2:18 pm 
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On the 383's it says on the paper that comes with the rings to make the top bigger cause the top ring goes above the water jacket so it will expand more. It also says to leave the bottom the normal size.

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 Post subject: Re: ring end gap
 Post Posted: Mon Feb 28, 2011 8:44 pm 
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WR169 wrote:
On the 383's it says on the paper that comes with the rings to make the top bigger cause the top ring goes above the water jacket so it will expand more. It also says to leave the bottom the normal size.


Well,...I've held my tongue as long as I can.

I do not prescribe to the second ring gap being larger then the top ring. I'll do the math for the top ring gap and subtract .004" from that and that is what I run. Not had any problems with it at all, and I have built more then a few engines over the years. :-$

It's my opinion that if you have a problem with getting too much pressure between the rings then you need to look for a problem. #-o

Don [-o<

jmo of course.

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 Post subject: Re: ring end gap
 Post Posted: Mon Feb 28, 2011 11:23 pm 
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want-a-be wrote:
It's my opinion that if you have a problem with getting too much pressure between the rings then you need to look for a problem. #-o

Don [-o<

jmo of course.


OK so if that's the case, then what is the down side of a wider second ring gap then? :-k Chuck doesn't even run a second ring and says that oil control isn't usually a problem with that engine?? :-k

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 Post subject: Re: ring end gap
 Post Posted: Tue Mar 01, 2011 6:16 am 
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I think there are a lot of guys out there doing it both ways with very good success. Heck, the stock stuff has a ton of gap on both rings and look at how long they are running now-a-days. Do what you think best Ken and don't think back about it. Main thing is to not but the ends together, then you will mess a few things up.

Don

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 Post subject: Re: ring end gap
 Post Posted: Tue Mar 01, 2011 6:31 am 
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I was told that if your running a vacuum pump you need to adjust the ring gaps a little different also...
Have to take a look and see where mine were set...

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 Post subject: Re: ring end gap
 Post Posted: Tue Mar 01, 2011 8:07 am 
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I dont understand the" do the math and subtract .004",is that just on the top ring or both?

The way i understand rings,if the pressure between the rings equalizes due to the seconds gap not allowing gasses to escape faster than they enter the top ring loses its seal....i found this from federal mogul
"The federal mogul engineers assert you do not want the pressure to equalize before and after the top ring.
If that happens there is no pressure to force it against the cylinder wall and seal the bore.If pressure is equal here then all thats sealing the cylinder is the ring tension,which isnt nearly enough.You have to have a pressure difference above and below the ring for it to work properly "

One other thing that has not been discussed is that the piston rings are also the part that removes the heat from the piston so if you only have one ring you have given up the cooling that accompanies having the second ring,from my understanding,the only reason for one ring is that the piston is so short above the pin the second ring wont fit.

So with all that being said how do zero gap seconds work correctly? I think the second in that case is all that is sealing the bore....any thoughts?


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 Post subject: Re: ring end gap
 Post Posted: Tue Mar 01, 2011 8:46 am 
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inVEGArating wrote:
from my understanding,the only reason for one ring is that the piston is so short above the pin the second ring wont fit.

That is the case with mine. The intake valve relief is so deep that there wasn't enough piston left between the top ring and pin for a second compression ring.

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 Post subject: Re: ring end gap
 Post Posted: Tue Mar 01, 2011 9:56 am 
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inVEGArating wrote:
I dont understand the" do the math and subtract .004",is that just on the top ring or both?


So with all that being said how do zero gap seconds work correctly? I think the second in that case is all that is sealing the bore....any thoughts?


4.155 bore x .0045 = .0186975 ring end clearance.

RE: Z gap second ring? Ran a set of those from Total Seal years ago before I learned that they were junk. Just another gimmick to sell parts, IMHO. Looked into the Z gap TOP ring they now offer and Rick got info from then concerning that ring and they state that there's a 10HP pickup using it but I'm more than a little apprehensive about this new "gimmick"! When or if (well known engine builder name inserted here) endorses and runs them then I might think about them differently. They are quite pricey also and since I'm "cheap" I just opted for the standard top ring with a napier second.

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