Define "expensive".....
Unfortunately, there are not a lot of good "bolt on" mods for a 250. The engine lacks breathing abilities and will need to come apart to get any significant gains in power. This can be remedied though: cylinder head porting, camshaft upgrade, intake manifold modifications for a larger carburetor, etc.
You could pull the head, port the valve pockets, have larger valves installed with a 3 angle valve job and a mill, slide in a performance camshaft, do a 2bbl upgrade, upgrade the ignition, and finish with some headers for under $1,000 (on paper) if you could do all the work yourself and find the parts cheap. In reality, costs are often double or tripple your initial, naturally conservative, estimate.
Or you could just put a $500 nitrous system on it as is and see what happens :roll:
What year is your Maverick? 2dr or 4dr (just curious)?
