Det45

I recently came across an old 2003 Hot Rod article claiming that they were able to get 400HP out of a stock 1991 5.0 HO roller short block using the stock cam, 165cc AFR heads, headers, and a set of 1.7 roller rockers. Is this article bull $h!t or can this be done? How were they able to increased peak RPM without changing the cam? Can anyone chime in on this one?








http://www.hotrod.com/articles/ford-...ngine-buildup/

Rather B.Blown

Well the engine they started with that was supposedly stock made 278 hp @ 5200 rpm, which is a huge anomaly right off the bat.

SilrBult

My take on dynos and dyno numbers goes like this: it is a very useful tool for comparing engine modifications, ie. how does one cam or intake manifold compare to another or what is the optimal ignition timing curve and or air fuel mixture for a particular engine combination. What it's not good for is comparing absolute numbers from one dyno or dyno operator to another. First off there is more than one type of dyno design and the different types can produce different readings. Not all operators are equally experienced and or skilled. There are different correction factors that can be used. Correction factors are necessary because test conditions can vary and a correction factor will equalize the results, or at least it should. Before the early '70's the auto manufactures used a correction factor that provided gross horsepower ratings. This made for impressive but unrealistic numbers. Starting around '72 the government mandated a change in the way engines were rated and used what is generally referred to as a net rating which isn't as impressive but is a much more accurate reflection of what the engine actually produces as installed in a car. It's true that EPA regulations in the '70's did result in some power losses, but a good deal of those losses had to do with the way the engines were rated. In any case the hot rod or performance industry still likes to use the older gross correction factors since it makes them look better. Most of the magazine articles you read use these gross ratings when they do a dyno test of an engine they've built or some part they wish to write about. These numbers aren't fake, but they don't necessarily reflect the level of performance you might expect if you were to actually put the engine in a car or the performance improvement you might be hoping for if you install certain parts on your car. I am not saying that performance parts don't work, generally they do, just don't take the horsepower numbers too seriously. When it's all said and done the only numbers that truly matter are time slips. Drag strip trap speeds [ not the ET, since chassis has a big effect on ET ] combined with vehicle weight are a much better reality check than somebody's dyno number claim. Lap times from oval tracks or road courses are less useful because of the huge number of variables eg. chassis setup and driver skill and consistency.