Well, i can't say what it's worth in HP, but my increase from 11.25 to 12.50 was worth 4 tenths and 4 mph. I will be honest and say i also ported the intake plenum and added an electric water pump as well, so not apples to apples, but the hp gain is much more than some may think. I try not to leave anything on the table anymore with my street/strip set up.
I agree, at least with the not being apples to apples part. Four MPH from a single point of compression is more that a little hard to believe.
Wallace Calculators gives a 600HP engine less than 5 additional horsepower when going from 11.25 to 12.5. Just one example, and not for a Hemi. But probably much closer to reality than the horsepower it takes to get another 4MPH. Which Wallace says would take about 17 more horsepower for each MPH.
http://www.wallaceracing.com/hp-cr-chg.phphttp://www.wallaceracing.com/hp-mph-increase.php
