Join Date: May 2004
Location: Ontario, Canada
6psi with a decent tune will last as long as your car will. The stock internals are certainly not ideal for boost, but not that weak. Detonation is the enemy, so as long as you stay a little on the safe side with the timing, you're good to go.
Sure, I've heard of/seen a handful of stock engines going out here and there with higher boost levels, but I'll guarantee you in all cases, it was due to the way it was tuned or previous condition of the engine that pushed it out the door.
Hell.....I know of several 4.6L Mustang guys running around with 9-11psi and 400+hp on the stock short block for years now without even the slightest hiccup. Again, keep the heat under control (conservative fuel and timing curve), maintain your engine and always run good quality fuel and you'll do alright.
*1990 Mustang Coupe, 5.4L*
Black on Black & Stroked 'n' Polked!!!