I was sending desktop dyno to a member on ***boat.... so I desided to for a gigle to see what kind of power my motor would not make.... not sureprising a 421 was not on there so I used its sister 389( basicly .030 smaller in bore, pontiac just over bored the 389 to get a 421 it was a cost saving thing they used the same casting.).... well the funny thing is with my set up it says I will only make 231 hp so I deside to run the factory specs and see what I get.... I got a whapping 239hp now the funny thing is that from the factory they came with 390 for a 2 barrel and 410 for a 4... now I know pontiac probly bsin those #s but off by more then 100 hp I think not.....I wonder if it has to do with the fact that desktop dyno does not compute D port heads any ways just something I thought was funny. Only with the hotz-totz heads could I get it to break into the 300 mark. Just something funny I found.