I would not be too concerned about the HP numbers, that engine will make torque.
The cylinder heads do not flow that well.
There are aftermarket cyl heads & Arias blocks & others w/4 bolt mains. IIRC
My friends customer had one at there shop in a Jenson Healey, IIRC if was 200 CI, turbo, blowing through DCOEs
MBHD
