$3000 is not really a lot of money in the realm of engine building. It would cost you about $1500 - $1700 to completely rebuild a 1.9 Opel to stock specs (replacing everything that normally wears). And this does not include upgraded components such as larger carburetors, intakes, labor to port the head, exhaust systems, ignition system upgrades, cooling systems upgrades, etc.
Now, if you are a "do it yourself" type of person, you can build a fairly healthy engine for $2500-$3500, plus accessories (as mentioned above), and make a streetable 140-160 hp at the flywheel. This will be enough power to easily let you lose your license for many years. The factory speedometer will no longer seem optimistic.....
The factors that will ultimately make up that last 20 or so hp are the carburetor(s), exhaust system, cam choice, and head work. I would place the emphasis of power-making ability on the cam and headwork, as the intake and exhaust can always be changed out easily later as the budget allows. Head work does not usually affect driveability, but it is the most expensive item on an Opel to make power. The cam choice will affect durability and driveability for a street-driven car, and it must be chosen in conjunction with the head work. I suggest moderate valve lift for use with stock rocker arms, in conjunction with substantially increased duration. I've successfully used a profile patterned after the old Chevy 409 engine (.435" lift, 242 duration @ .050" compared to .385" lift for a stock Opel solid cam and 202/205 duration @ .050"), and it worked well for me for over 50k in a street driven and track-raced Opel. No broken rockers, no hard starting, no extreme wear on the valvetrain.
Bob
