The nitrous, if being added with the appropriate amount of fuel and with the ignition timing being correctly retarded, is not detrimental to an engine but the additional horsepower that's produced as a result can be. If the pistons are cast, piston wall clearances are too tight, ring end gaps are not appropriately opened up, connecting rods are marginal and/or fatigued, and a myriad of other things are not up to par to handle an obscene increase in power, then engine parts will suffer in short order due to the increase in cylinder pressure and heat that comes into play when nitrous is used. Nitrous is an inexpensive power adder if the engine is built to handle the anticipated horsepower being produced. And even if everything is right, a gasoline solenoid can fail thus bringing the engine into detonation or a lean condition and thus destroying it anyhow. On a stock Y, a 150 hp shot would be an invite for a quick death. Might get away with it for a handful of hits if you're close with the fuel mixture and ignition timing, but pistons and/or rings would suffer reasonably quickly.If the engine wasn't initially built with nitrous in mind, then it's a good idea not to use it as clearances for a nitrous engine are considerably more with the additional heat in mind. Camming also varies with nitrous in that it likes an increased lobe centerline to reduce blowthru at the exhaust during overlap.