Is your crank pulley keyed onto the crankshaft, or just held on with a single bolt like my Subaru?
If it's not keyed, adding torque this way will unscrew the pulley. It's meant to drive things that put drag on the crank, not receive power from things that speed it up.
I'd be tempted to use this motor for electric-only city driving, moving in and out of parking lots, etc etc. But of course you have to spin the engine internals, which will sap some power...
__________________
|