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.
That kind of gain isn't happening just by bumping compression up a hair over a point.
I suspect your gain was more because everything you had was too “ big” for the compression you had( in other words an under performing combo) and the bump in compression helped make the combo “ fit” better. In other words run more like its supposed to.
The shop doing my new engine, was taking to them about gains. Going from10 to 1 to 12.5 compression. 360 to 418 cubic inches. Cleaned up heads to mildly ported heads, dual plane to single plane. Same cam( too big on 360) to “ about right” on 418.
We are hoping for about an 80 horse gain from all of that. Seems pretty reasonable.
When you see the kind of gains you saw with that compression bump, it's more fixing an issue you had, than it is a +-3% gain from a little more than a point in compression would net 4 tenths and 4 mph.
Otherwise everybody on here would be milling heads a little and or changing to thinner head gaskets tomorrow to reap such gains
