I was told to figure in a 30 HP loss, from the flywheel to the rear wheels.
When I had mine Dyno'd for the Forza Motorsport 2 Game on XBOX 360, my stock 2.4 liter block, E88 head w/ stage 2 cam (477/280) 6-into-1 header, dual SU's (untuned) ZX dizzy, 5-speed tranny and 2.5" exhaust had a total of 135 RWHP and 133 Ft lbs torque.
So I basically had about 165 HP at the flywheel with a few mods. But now that I have Triple Webers, Mallory Unilite Dizzy, MSD 6AL, Promaster 65kv coil and an R200 diff, that has been increased to almost 180 at the flywheel.
I have an F54 turbo block being built in Oregon that has been promised to put out over 210 HP. It'll have a 40 over bore, stage 2 cam in the N42 head that'll be ported and polished with bigger valves, rebuilt SU's with better needles and valves, 6-into-1 ceramic coated header and 2.5" exhaust. Same unilite, MSD and promaster coil. The crank and flywheel will be ballanced and the Flywheel will be lightened to about 16 lbs.
Hope that gives you a little better insite.
Dave