Roush 427r only made 400whp :(

[DAVID GAGNARD]

[quoteCrank hp is 550hp (546 exactly), but after break in miles, I strapped it to a dyno and it put down a measly 401whp. That is a HUGE drivetrain loss. I was expecting 15% loss, but this is near 27% unless Roush is over rating their motors.
][/quote]

There has been documented cases here (not going to look for them,would take me all day and half the night) of 100hp loss just thru the side pipes alone,not counting restrictive air filter or "normal" driveline loss.......

not knowing what size/type/kind of side pipes/headers/air filter you are running, I could easily believe a 27% hp loss.......

easy way to tell,go back to the chasis dyno, and take off the air filter and disconnect the side pipes from the collectors and run "open" headers and then compare the numbers.......you will likely be surprised......

David