Nitrous on a 318.....how much will it take

72 Satellite eh? Make sure it's pointed straight down the track, and has lots of shut-down area. Easy 350/400/450 HP, enough to break everything factory behind it when it hits, and to get you more speed than the factory suspension,steering,tires or brakes, can handle .
On the flipside, this is a great way to get a well-sorted 318 streeter into the low 13s.
What's that B weigh? maybe 3800 race weight? well just 380 would get you a P/W of 10/1 and that goes 107/108 which is 12.4 in a SuperStock chassis. Add about .5 for a street chassis and another .5 for a lousy 60ft, so that totals 13.4.
But that's with a NA engine for starters. The boosted engine is gonna make a lot more average power, so if you can get the power on early, you might be tickling 12s. Make sure the rest of the car is up to it.