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Why the difference in power?
ring seal due to the differences in the expansion rate between the aluminum block and steel sleeves is what I have been told. I heard this from a relaible source that has used both types of block that the aluminum block would only hold minimum (less than 5 inches)vacume on start up cold and end up with positive crankcase pressue at the end of the run, 45 seconds to a minute and fifteen seconds later  The iron block holds 17 inches on start up and crooses the finish line at 15 inches or more depending on how many runs are on the rings and pistons. This is on a boosted 2000+ HP motor  IHTHs
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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