I hate to start this thread up again, after it had pretty much run its course...but I have an oportunity to get what could be interesting information. A good friend of mine had Norm Grimes build him an all aluminum, blown-injected gas, small block chevy for his sand car. When Norm dynoed it it had exsessive blowby, which Norm attributed to the aluminum block flexing. My buddy is now buying a cast steel block from Dart and they are going to transfer all of the components from the aluminum block to the steel block, then they will dyno it again. This should give a good comparison between the aluminum and steel blocks. What do you think, interested in the results? Unfortunately, it will probably be a month, or more before we hear anything.