do u need to mod engine if u go 9 psi or will the stock pistons handle the boost. i have 4.6l 2v 5 sp mustang and going to add k-b s/c please help if u can thanks

 

9lbs will be fine as long as you have a good tune. Most supercharger companies don't recommend over 8lbs of boost, but 10lbs is pretty much the safest "understood" boost pressure for a stock bottom end. I've seen alot of people running 12+ lbs without any problems, really it has more to do with your tune and how high you wind up. T&J recommends not exceeding 6k rpm if your running 10+ on a stock engine, so I don't see where 9 would be a problem.

 

Boost has very little to do with how the engine will stay in tact. I don't like seeing a lot of people say "Will 10 lbs. kill my motor? If I run X amount of boost, will it blow?" It's not about the boost at all, really. It's the power you're making at X amount of boost. If your rods, pistons, crank, whatever it may be.. can't hold the power, then it's over for the motor.. or it just won't last a very long time. There's also other things that play factors in a good "reliable stock block big horsepower" motor too. Like, tuning, etc. Think about it.

 

Boost directly corresponds to HP, but I see your point.

 

obviously, hp is a result of boost, but there is no set equation for boost to hp.