Cast Crank Strength

I wouldnt use them over 150hp. It's more than detonation when you start going with a hevier shot. The piston itself is under much more stress. Think of it like this. Detonation is a hammer blow. Hard, and very abrupt. It creates a lot of stress over a very short amount of time. But the forces from pressure from the burn and from the directional changes all try to deform and break the piston too. The materials in a forged piston are very strong, and can take the stress by deforming slightly or "flexing". Cast pistons can also do this, but to a lessor extent. Hypereutectics cant, because the material is like tool steel. It's strong and light, but brittle. So instead of flexing, they fracture. There are limits on what the cheaper stuff can do. In addition, you are talking about adding stress to the block, the main caps, and the crank itself. Cast Mopar cranks are good, but the reason the 4" ones can take so much is they were designed from the get go to be very strong. They have large radii and are thick where they need to be. A factory 318 crank is light, strong, and will far exceed the stock hp levels. But to ask it to go to 500+hp under nitrous IMO is a recipe for a short service life. They will crack. You may not notice until the whole thing comes apart. Also, being that nitrous is a sudden power increase (and decrease) the block and mains are under a lot of stress. The mains at minimum should be studded, and the weights of rods and pistons should be kept as light as possible. Now, all that being said, you have got a nice foundation for a safe car with the right stuff to support bigger NOS use. So if you have 4 of them, and can sacrifice one, perhaps doing a ring and bearing job on one and them gassing it until it expires would be fun AND educational..lol. The Neon 2.0SOHC took over 250hpo of gas before it lost a head gasket with a hasty tossed on Cheater setup. So why not? I would either decide to "do it right" or dont spend more than a minimum and go have some fun with it.