[ByronRACE]

Strength limit of the engine is based largely on the tune.

If AFR and Timing aren't correct for nitrous use, everything is at risk.

I strongly recommend buying a wideband AFR system first. This will let you tune the air/fuel ratio so you don't end up running nitrous on a lean mixture. Do that one time at full throttle, and you'll have junk for an engine. It's not worth the risk when a wideband AFR meter is now in the $300 range.

Next, assuming this is a wet system that has both fuel jets and nitrous jets, start with the recommended jet sizes for both and go for something sane like a 100-shot.

Then, set the timing for about 4deg below the edge of detonation. If your engine begins to ping NA at 34deg total, set the timing to 30 total. That should be more than enough retard to keep the engine happy when on the bottle. Creep back up on the advance slowly and carefully, and only if you know what detonation sounds like and can hear it over the engine. Otherwise, leave it alone. The power difference isn't worth the damage.

Drop your plug gap down to .032-.034. If you experience any misfire, drop it more. Or, buy an ignition amp.

To test, disconnect the nitrous solenoid...go drive it...and make sure the mixture goes PIG RICH when you activate the system. That tells you the fuel control is present, and the engine should be safe for N2O. Then, reactivate the nitrous solenoid and try it again. If the recommended jets are correct, the WOT AFR should be somewhere between 10:1 and 11:1. I don't recommend you run the mixture any leaner than 11.5:1; the power gains aren't worth the potential damage.

How much power can your stock block take? Probably close to 500rwhp before it splits down the valley or rips the webs out by the mains (seen both). Rods are pretty strong. Usually the block goes first. I wouldn't recommend more than 450rwhp if you want it to live a long happy life. That means you can probably run a 150-shot on it if you so desire. Keep an eye on AFR, don't ever skimp on fuel octane, and it should live a long time.

And as suggested, if you want to "have your cake and eat it too", get a retard box that drops 4deg of spark when you arm the nitrous system...that will give you max performance in both modes without sacrificing NA performance.