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Discussion Starter #1
All right N2o guys need a little help. piston ring gap for a 250 shot on top off a 700 HP BBF running on E85? I lifted the top ring land off of two of my pistons last trip out with only a 125 shot second pass boom. My ring gap on tear down was set to .028 too small this was the top ring. I was thinking .008 X the bore size to play it safe when i put it back together and about .002 larger on the second ring? What do you pro N2o guys think. I i'm sprying with E85 not race fuel.

Thanks in advance
 

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All right N2o guys need a little help. piston ring gap for a 250 shot on top off a 700 HP BBF running on E85? I lifted the top ring land off of two of my pistons last trip out with only a 125 shot second pass boom. My ring gap on tear down was set to .028 too small this was the top ring. I was thinking .008 X the bore size to play it safe when i put it back together and about .002 larger on the second ring? What do you pro N2o guys think. I i'm sprying with E85 not race fuel.

Thanks in advance
If you lifted the top land at .028, you may have other issues. You are aware you can left a top land from running over rich. Even more so with E85.



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steelcomp was here
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If you lifted the top land at .028, you may have other issues. You are aware you can left a top land from running over rich. Even more so with E85.
X2... .028 should hve been plenty.
 

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Discussion Starter #4
If you lifted the top land at .028, you may have other issues. You are aware you can left a top land from running over rich. Even more so with E85.
Thanks! Learn something new every day! E85 tune is new to me. But i can tell you this. Started out way lean just tuning the carb not N20. engine was pulling up to 5600 and then doing the lean popping. as i jetted up rpm increased. Final result was a .156 orifice jet in secondaries and 97 with power valve primary. and RPM was 6200 RPM WOT no popping. Now with N2o engine was surging a little from 6300 to 6400 had 5 degrees of ign. timing pulled out with my nitrous controller. The fuel pressure was et to 6 psi. Very poss able to rich on n20??? i thought it was a lean surge on the second pass. Just because of the carb tunning.

thanks
 

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Thanks! Learn something new every day! E85 tune is new to me. But i can tell you this. Started out way lean just tuning the carb not N20. engine was pulling up to 5600 and then doing the lean popping. as i jetted up rpm increased. Final result was a .156 orifice jet in secondaries and 97 with power valve primary. and RPM was 6200 RPM WOT no popping. Now with N2o engine was surging a little from 6300 to 6400 had 5 degrees of ign. timing pulled out with my nitrous controller. The fuel pressure was et to 6 psi. Very poss able to rich on n20??? i thought it was a lean surge on the second pass. Just because of the carb tunning.

thanks
Not saying it couldn't be lean either. Just saying unless that ring is sitting right at the top of the piston, .028 is plenty for that shot.



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If you lifted the top land at .028, you may have other issues. You are aware you can left a top land from running over rich. Even more so with E85.
Hmmm.... maybe I should check your IP to make sure this is not a Hat Alias. :D
 

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First of all if you feel surging, it's from being lean... too rich and it will just "lay down" and quit pulling. Second, Nitrous creates oxygen, so if you suspect a lean condition it's because you're not adding enough fuel for the added oxygen the NOS is providing. Third, you should be reading your spark plugs after a steady cruise, then trying your changes (the steady cruise cleans up the plugs) and reading the plugs IMMEDIATELY after your run. E85 is a whole different deal, so I may be comparing apples with pistons... (no pun intended) And I completely agree with steelcomp, .028 is plenty ring gap and I would go no more than that. I also agree with gn7 on other issues causing the top land to come off, and that could be from compression ratio, to piston design/correct application, and the host of other mechanical issues that are possible, although I can't help on the rich E85 issue and don't understand why it would cause that but anything is possible... did it melt or just plain break off? Also piston to cyl wall clearance is critical on the squeeze, a tapered wall would be trouble, but this is based on how much you trust your machinist. Also what ign system are you using and what kind of plugs/gap are you running. I might also suggest calling your Nitrous kit manufacturer to ask for some advise tuning your combo without eating hard parts... Anything you decide to do, verify it with multiple sources before jumping in i.e. engine builder/machine shop, NOS company and someone who you can also verify has had experience tuning NOS setups. Every combination is unique when tuning so be careful & keep us posted.
 

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My je catalog shows .007 x bore size on top ring and .0075 x bore size on second ring in a race app
in moderate turbo/n02 .005 x bore and .0055x bore on second.

I run the .007 x bore for a little safety margin in mine (565) gas ported .043 rings j/e pistons

what kind of fuel system are you running and what octane fuel??

I would also check bottle pressure and that the tank is full on every 3-4 pass.some guys are heating there bottles to get the pressure up.

You may want to send your solenoids in for a rebuild also before you spray it again,cant be to safe

Thats just me n02 failures can cost$$ big money

mine only activates during the last 1/4 inch of wot with the button pressed at the same time,also i run a msd timing computer

best of luck.
 

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Discussion Starter #9
Thanks every body!

Here is a little more info on my build.

BBF 466
Compression ratio 12.8-1 Pistons where KB-401 domed Hypers going to forged
Cam Custom solid roller 665 lift 278 duration at 50
Heads TFS CNC'd 325 80cc combustion chambers
Carb 1050 quick fuel E85 conversion
Spark plugs NGK-8 gaped to .032
Ignition system is summit capacitive system like the MSD 6AL with Jacobs nitrous master mnd controler that will shut of N20 if fuel pressure drops.

Fuel system -10 from tanks pulled by a Mallory 250 alky pump to BG 4 port regulator -8 to carb She is getting plenty of fuel Solid 6 psi with N2o flowing and feeding carb. one port go's to fuel solenoid.


Pistons did just plan break off no melting i will post some pics when i can!
 

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Hmmm.... maybe I should check your IP to make sure this is not a Hat Alias. :D

hil:)hil:)hil:):))eek:))Reality NO no no! Hats arguement was fuel was the fix all. Fuel took care of all pistons failures.
Although everything the OP says sounds like a lean condition, the cap was plenty. So there is something else that took down that piston.
I would like to know if this land failure was a lift, or busted off that apears as a lift.

These are Jeff Procks words, not mine:
Failure Modes
The two most common nitrous-motor catastrophic failures are blown head gaskets or burnt pistons. A blown gasket can be hard to run down because it can be caused by either the wrong air/fuel ratio or detonation (or both, since the two can be related). If you just treat the symptom with improved gasket sealing, there's a good chance the next failure will be with the pistons.

Piston failures are easier to diagnose. You'd think going too rich is safer than too lean, but if liquid fuel trickles down past the rings, the resulting distress can lift the rings upward. As Nitrous Express puts it, "Many nitrous failures are caused by running the engine excessively rich. Contrary to popular belief, richer is not necessarily safer."

On the other hand, burning a trough down through the rings into the skirt usually means you are both too rich and have too much timing in that cylinder. "But if you burn a hole through the top of the piston, you are running too lean. If you start the burn and there's nothing left to burn, everything's gone--you'll just burn the aluminum," adds Musi.



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hil:)hil:)hil:):))eek:))Reality NO no no! Hats arguement was fuel was the fix all. Fuel took care of all pistons failures.
Although everything the OP says sounds like a lean condition, the cap was plenty. So there is something else that took down that piston.
I would like to know if this land failure was a lift, or busted off that apears as a lift.

These are Jeff Procks words, not mine:
Failure Modes
The two most common nitrous-motor catastrophic failures are blown head gaskets or burnt pistons. A blown gasket can be hard to run down because it can be caused by either the wrong air/fuel ratio or detonation (or both, since the two can be related). If you just treat the symptom with improved gasket sealing, there's a good chance the next failure will be with the pistons.

Piston failures are easier to diagnose. You'd think going too rich is safer than too lean, but if liquid fuel trickles down past the rings, the resulting distress can lift the rings upward. As Nitrous Express puts it, "Many nitrous failures are caused by running the engine excessively rich. Contrary to popular belief, richer is not necessarily safer."

On the other hand, burning a trough down through the rings into the skirt usually means you are both too rich and have too much timing in that cylinder. "But if you burn a hole through the top of the piston, you are running too lean. If you start the burn and there's nothing left to burn, everything's gone--you'll just burn the aluminum," adds Musi.
Exactly Bob!!!! I've done some reading over on yellowbullet and it seems like you can hurt a motor quicker running to rich vs running to lean.. Obviously if you just take the NOS jets out and whack the throttle then it will kill a motor faster.. I run .026" on my top ring with a 125-150HP with the top ring way up the piston 1.125 CH and we haven't experienced any problems (knock on wood)..

Amango, what type of NOS system do you have and what's the tune up? 6 psi seems a little high to me.. Did you actually flow the NOS system? We run ours @ 5.5PSI.. I would think you would have to have the NOS system way out of whack to lift a ring gland on a 125 shot.. Post this over on www.yellowbullet.com.. They have a Nitrous forum, great info over there!!!!!!!
 

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Thanks every body!

Here is a little more info on my build.

BBF 466
Compression ratio 12.8-1 Pistons where KB-401 domed Hypers going to forged
Cam Custom solid roller 665 lift 278 duration at 50
Heads TFS CNC'd 325 80cc combustion chambers
Carb 1050 quick fuel E85 conversion
Spark plugs NGK-8 gaped to .032
Ignition system is summit capacitive system like the MSD 6AL with Jacobs nitrous master mnd controler that will shut of N20 if fuel pressure drops.

!

How bout the reason be they are a HYPERUTETIC piston????????
 

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.....Amango, what type of NOS system do you have and what's the tune up? 6 psi seems a little high to me.. Did you actually flow the NOS system? We run ours @ 5.5PSI.. I would think you would have to have the NOS system way out of whack to lift a ring gland on a 125 shot.. Post this over on www.yellowbullet.com.. They have a Nitrous forum, great info over there!!!!!!!
+1 what Vince said and Yellow Bullet...
 

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iv seen several sets of kb self destruct from lack of enough end gap, even N/A, if theres enough left to tell Id bet the broken area is at the end gap.
 
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