Aren't you limited to the limits of stock internals. After years of research I read 400 is the safe limit even tho blowers can push that.
Back when this forum was very active people constantly argued what the upper limit was. Some said 400 rwhp other more. ProCharger defined the upper limit in terms of boost. Their online table said 12 psi for Windsors motors. 8 psi for Romeos. The Windsor motor (99-early 01) is slightly different than its Romeo counterpart (late 01-04). It was designed to be a truck engine. If I remember correctly its piston has an 18cc dish instead of a 12cc dish. Its compression ratio is 9.0:1 instead of 9.4:1. It was designed as a truck more and even has slightly different connecting rods. The same ones used in the 99, 01 four valve Cobra. All of those little things made the Windsor motor respond a little better to boost than the Romeo. But not very much.
Tuners at the time usually said that 380 rwhp was safe on an otherwise completely stock motor. But people pushed that up with other mods so the general rule of thumb was that 400 rwhp is generally safe. Motors with a bad tune or having undetected internal problems have blown up at 380-400 rwhp. Its not completely safe but it is generally safe.
When people throw out numbers they generally don't list all the mods. A lot of people pushed even higher saying 450 was safe. A couple of people said 500 because a dedicated race car was running that. What they did not say was the high horsepower motors had cams and were running E85 fuel. They also didn't talk about how long they would last at that level. Because of this there were a few that tried to get to 450 on boost alone. I remember a couple. One person was running 13 psi (around 425 rwhp). His motor last about nine months. Another pushed it up to 14 psi (around 435 rwhp). His motor didn't last that long.
What is known is that cams add horsepower without adding a lot of additional stress on the rods so theory and street tests seem to agree that the general safe horsepower rule is 10 psi, 400 rwhp without cams and near 450 rwhp with cams (probably closer to 440 but everyone uses 450) using 93 octane street gas.
P.S. Dynos have to be calibrated for barometric pressure, humidity and temperature. I have seen some very optimistic dynographs posted listing very high correction factors for the recorded barometric pressure, humidity and temperature. I'm not sure that some installers didn't tweak the system to make their customers happy. Also there are two different correction methodologies that use entirely different baselines. STD usually reports a higher horsepower than SAE. I remember one member used raw numbers instead of corrected. It was a particularly cool day and both correction factors calculated a lower number.
