Best Ring Package for N2O

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#1 Post by **John_Heard** » Tue Jan 20, 2009 6:57 am

Need to rering my engine this winter and I'm going to rethink the ring package. Currently using .043x.043x3/16 w/hellfires and low drag oil rings. I've got three holes that are down a bit, not real bad but problem is the engine has been getting oil up in the intake from somewhere. I'm suspect of the low drag oil rings I've got in it and I'm considering going back to a standard tension oil ring. The only time it appears to get oil up in the intake is during coast down after a pass, for example a few weeks ago I took it out for a drive. Went down the highway, got on it a bit, then did a nice high gear burnout. No oil in intake at all, so I'm pretty sure it's doing it when coasting down when intake manifold vacuum exceeds pan vacuum.

Anyway, looking for input from guys that might have ran into this before. If I go back with low drag oil rings I'm thinking that the trick might be to use a J hook/Napier 2nd ring. I'm wondering if that would solve the issue (if that's what's going on). The other thing might be an intake leak, I'll verify that very soon, engine is just about ready to get tore down.

Hitchcock · #2 Post by **Hitchcock** » Tue Jan 20, 2009 9:39 pm

Low tension rings...vacuum pump?

#3 Post by **John_Heard** » Tue Jan 20, 2009 10:09 pm

Yes its got a vacuum pump & 5 Stage dry sump, vacuum relief valve was set at 10 inchs.

sunsation540 · #4 Post by **sunsation540** » Tue Jan 20, 2009 11:20 pm

the std tension stuff works well for me are the pistons gas ported? hellfire for sure up top are your current 2nd rings molly or a cast?

#5 Post by **John_Heard** » Wed Jan 21, 2009 6:03 am

Yes they are ported (top) and cast 2nd. I really hate to have to put std tension oil rings back in it, I sure like how easy it spins over with the low tension stuff... I'm just wondering how much better the Napier 2nd's do on oil control and if that would be enough.

stroker1 · #6 Post by **stroker1** » Wed Jan 21, 2009 12:10 pm

Maybe I'm just stupid, but is there anyway to reduce windage in the crankcase or any trick way to reduce manifold vacuum when coasting down? Seems like you're saying it's mostly a problem when the motor is coasting down.

Like I said, it's a retarded idea, but just wondering could you maybe rig up an airbleed that would work only when coasting down? Probably wouldn't work too well unless you do WOT shutdowns.

ProCar · #7 Post by **ProCar** » Wed Jan 21, 2009 10:17 pm

John, the n20 will turn the crank just fine with coil springs in the third groove. I ran HIGH tension rings once and lost very little n/a on the pump. It was drier than an old nun. Std. stuff will clear things right up, and I never oiled with them. Don't worry about it, just do it. I promise it'll work. Remember, a dedicated nitrous engine is simply a case that holds shit together, containing the anger, like a nitro motor. It's no longer about finesse, it faster to get more spray (fuel) in there and seal it than all the trick bs we can think of.

This isn't a sexy answer, more like a sleazy one, but it ain't in the second ring unless they are flat. Still, I would never run anything less tight than a standard tension oil ring. Peace!

#8 Post by **John_Heard** » Thu Jan 22, 2009 7:27 am

stroker1 wrote:Maybe I'm just stupid, but is there anyway to reduce windage in the crankcase or any trick way to reduce manifold vacuum when coasting down? Seems like you're saying it's mostly a problem when the motor is coasting down.

Like I said, it's a retarded idea, but just wondering could you maybe rig up an airbleed that would work only when coasting down? Probably wouldn't work too well unless you do WOT shutdowns.

Might need to be a pretty big air bleed given the size of the engine, not sure how I would do that one. I know other guys running low drag rings and they haven't ran into the problem, but maybe I'm not getting good enough ring seal to make it work.

I hear ya Patrick, that's probably the route I'll go. I'm still curious if the J hook/Napier design 2nd would allow a person to get away with the low tension oil rings and not have the issue. I never had the problem before with regular tension rings on previous engines. I did get the intake off last night and found no evidence of leakage on the manifold gaskets. They show a nice 360* impression all around the ports, at this point I'm assuming this is a oil ring issue.

ProCar · #9 Post by **ProCar** » Thu Jan 22, 2009 7:38 am

John, with a dry sump engine, 20" isn't a problem. I know a Cup builder that says there is virtually no benefit until 9". Why only 10? I'm not trying to bash or be critical. I hope you know we're beyond that.

I've never used anything but a standard second, maybe something other will work. I have worn second rings flat because of all the fuel in there, so a really sharp edge seems fragile, esp. with the coarser wall finishes nitrous engines like (to hold more oil).

#10 Post by **John_Heard** » Thu Jan 22, 2009 7:56 am

Why only 10"? To be honest I just never got around to turning it up more. I was thinking more like 12 or so, I've heard of wrist pin issues above that? I haven't done anything to increase wrist pin oiling like squirters or whatever. Can you get away with 20" without doing something to oil them, or special coatings?

supernova · #11 Post by **supernova** » Thu Jan 22, 2009 9:15 am

Hey John,
I'm with pro car on this one. I run std. tension rings only and have never seen any problems.
Low tension rings are great for pro-stock but must of use in the real world don't live in that relm of racing. Perisidic drag doesn't hurt a n2o motor I promise.

And yes Helfire's only!

jmarkaudio · #12 Post by **jmarkaudio** » Thu Jan 22, 2009 10:20 am

Cup cars run a LOT of special coatings, like DLC on the pins. Anything over about 16 could be an issue.

ProCar · #13 Post by **ProCar** » Thu Jan 22, 2009 1:39 pm

20 inches is ok, the pump is outside the pan, and the average engine turns the crank only 600 times under power in a quarter mile run. Coatings are ok, used them, but in 700" nitrous engines that take a serious pounding there are no coatings that make much of a difference as all the tolerances are whacked out by the time the 11+ inches of aluminum deck gets warm. Setting the cam at .009 lash to see it open to .028 is a trip. They also detonate all the time, and no coating survives the constant abuse.

Cup engines are so sweet, so perfect, and run so long at a time... Coatings are a nice leg up.

ProCar · #14 Post by **ProCar** » Thu Jan 22, 2009 1:41 pm

John_Heard wrote:Why only 10"? To be honest I just never got around to turning it up more. I was thinking more like 12 or so, I've heard of wrist pin issues above that? I haven't done anything to increase wrist pin oiling like squirters or whatever. Can you get away with 20" without doing something to oil them, or special coatings?

Done it, seen it done, let it eat. You'll never see 20" anyway, right? Nitrous engines pass too much past the rings. I'd be real happy with 18.

#15 Post by **John_Heard** » Thu Jan 22, 2009 2:46 pm

ProCar wrote:Done it, seen it done, let it eat. You'll never see 20" anyway, right? Nitrous engines pass too much past the rings. I'd be real happy with 18.

Interesting... No, it probably won't be able to make 20. I'm not certain how much it can make unrestricted, might have to look into this a bit more.

Best Ring Package for N2O

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