It just took a bad turn when some people put THEIR OWN limitations on the build. You asked a blanket question - 900 NA H/P = how much. Others created the drama with all THEIR limitations, such as inline valves, new vs old parts, etc. Bottom line is - there is no simple answer. The guy that can shop wisely - including "seasoned" parts, use patience while buying parts, get his machine work done CORRECTLY at reasonable prices, and can do a lot of his own grunt work will pay dimes on the dollar to the guy that buys all new stuff and just writes a check when the pump shows 900 HP.

And here's the real rub. People that use MPH as a true gauge of H/P must be clueless to ALL of the things that affect trap speeds. Weight is obvious. Driveline loss is too, to a certain extent. Engine accessories - I've never seen anybody use a working alt on a dyno pull (at this level). The smarter ones will start to consider the aero package, and that resulting drag. But something NOBODY ever seems to grasp is that a dyno cell is not a real world scenario to the airflow introduced to the carb. While you can jet for max installed H/P - it does not mean you are making the H/P that it did on the dyno. You may gain H/P by having an efficient hood scoop/air pan setup that draws air from a cool high pressure area. But you can also lose it by drawing your air from a hot low pressure area. Look how much power Pro Stock cars lose at Denver - same thing - lower effective "air pressure". There can easily be a 50 H/P swing from the most honest dyno numbers to the H/P the engine actually makes in the car. And I'm sure there are other things that affect the H/P to MPH equation. Point is - there are too many variables to use the weight/MPH ratio as a way to accurately judge an engine in all cases.