I was wondering what has to be done to the rings and gaps if you are going to use nitrous. I have heard different things and was wondering if you guys had any feed back. Also.. how much juice can a set of good forged pistons handle if used rarely and timing and gaps are set correct.

-Mark

well as far as i know most companies give advice where to set them for use with Nitrous, but of course the gaps need to be spread to deal with extra heat in the cylinder when the nitrous is on

As Gib suggested, call the piston manufacturers for specifics. 

Just know, that to operate nitrous properly you can't simply put the switch on "kill" and go.  Much comes into play for optimal use... nitrous jetting, fuel supply and pressure, ignition timing, valve timing, gearing, etc.  It's a long list.  If you understand nitrous and play with it properly - it can be a fabulous power adder.  Use it incorrectly, and you'll burn up and/or dump the engine's guts onto the pavement.

If i am not mistaken you must also use racing gas for applications over 150 hp correct...?  

Not necessarily, much depends on your dynamic compression ratio.  A 9.5cr motor with a 150hp shot would likely be fine on premium pump gas - provided you perform all the other requirements (fuel supply, timing, etc.).  

But let's just say this...  the more you squeeze the motor, along with greater compression, the higher the octane requirement.

if he had easy access to racing gas and was willing to put the money down for it though wouldnt the higher quality fuel pick him up power due to the extra RPM's associated with Nitrous operation?

Possibly.  Particularly, if the engine combo supports usage at such a higher rpm (e.g.; heads and cam are still flowing within their optimal range). 

Remember too, there can be a point where you're running too much octane.  Anything beyond that point is a waste.  Obviously, that octane level can/will vary by engine combo. 

* An interesting phenomenon:  Look at dyno sheets from nitrous engines.  Often, the more you spray a motor the lower its peak power rpm.  Nitrous doesn't necessarily = more rpm use. 

wow i had no idea of that, i guess i havent been around Nitrous engines, what is the technical reason for the drop in peak power RPM?

I'm not entirely sure as to why.  My speculation is that optimal volumetric efficiency (VE) is achieved earlier in the rpm range due to the increased combustion process of nitrous. 

I'd welcome other's points of view on the matter.

Do you necessarily have to run racing gas with higher shots of NOS or can you hit up the octane levels when you plan on using the juice? Could you possibly use some quality octane boost or fill up at the airstrip with some jet blue or higher grade fuel such as 104 or higher octanes?

Again, there's no definitive answer to your question.  Much depends on what compression you're running and how much you're spraying the motor.  However, it's better to err on the higher side of the octane demands (and carb jetting) when nitrous is used.  

* What's your engine combo or set-up? 

Engine Combo:

SBC 406ci, 4340 crank, 4340 H-Beams, Forged Speed Pro Pistons, File fit plasma moly rings, Dart Iron Eagle heads fully ported, Comp Cams .502/.510 224/230 duration @ .050 (with 1.5 rockers, may go with 1.6 to hit up the lift) Pro Magnum Roller Rockers, Edelbrock RPM Air Gap, Carb undecided, (Barry Grant or Holley Street Avenger) Complete Milodon Oil System, 1 5/8 or 1 3/4 headers (Undecided, not sure which would be best for engine output) Mallory or MSD ignition, Compression ratio is 9.8:1 ( Any guesses on power output?) Engine would most likely never see more than 250 shot.

I had read in CHP about the street gas drags that they did and were limited to 93 octane gas but a few were still able to get away with up to 300 hp shots. Are you able to handle more nitrous if you run a controller to gradually ease the NOS in?

A 250hp shot is quite a bit.  I'm guessing your combo is in the 425hp range.  With a 250 pill, you just added +50% output, and tremendously magnified the stress on the bottom end and chambers.  Your forged pistons, rods and crank could likely hold up to the shot (provided you have ample fuel and pressure, and the timing is adjusted properly). 

It's other things I'd be thinking about.  I would only hit it that hard if I had 4-bolt mains, rings gapped for nitrous use and a cam with much more exhaust duration.  You need to keep that exhaust valve hanging open much longer to get all that stuff out of the chamber.  Also, with a healthy amount of juice, consider a cam with a wide LSA (+110).  You'd be smart to install a cam designed for the level of nitrous you plan on using (call the cam grinders - I think they'll agree).  Even with 9.8cr, I'd use at least 100/105 octane fuel with a 250 shot.  I'd opt for 1 3/4" pipes with a 406.

The controller - or staging unit -  will minimize the sudden jolt from a healthy shot of juice, yet, when you're full-tilt into the bottle... a 250hp shot is a 250hp shot.

* There's several articles in various publications about spraying the snot out of motors to see what they can handle.  Don't fall prey to the intrigue.  It's one thing for a publication to walk the ragged edge, it's another when it's your coin.  If my opinion seems conservative, it's because I've seen plenty of grenaded motors from improper use of nitrous.

I was wondering what has to be done to the rings and gaps if you are going to use nitrous.

 From: http://www.speedomotive.com/Building%20Tips.htm