i have no persoanl experience with the oddfire buick 225 nor the oddfire 231(3.8) just the laster buick 231 and 4.1 engines but mainly buick 300/340/350
but it all shall apply as they were all dirived from the buick 215 :-)
the 3.8 wasnt tuned/built for performance, but rather economy...so they stuck a :pokinit:ty cam in it, tuned the distro for ecomonly and pair it with a car that had 2.41s in the axle!
but yea...it's just like building any other engine
pair of headers and 2.25 duals, 4v intake(aftermarket is easier then finding one off a 4.1 engine) 390 holly or 400cfm carter/edelborck on a stock engine 500cfm edelbrock on a stout one.
chevy 250 distributor cap with evenely spaced terminals and a hi-volt coil kit.
can tune the distro with more advance all in before 2500 rpms with probly no more then 34 total timming something like 16 inital 12 advance and about 5 or 6 vacumme
2600-2800 stall
a nice midrange cam will wake the engine up too(poston buick and ta performance are the best) something with .420 lift anything more you'll need the guides cut.
i beleive you can put oversized valves in
good mild street port will do wonders also( can do for free if you have a dremel)
4.56 gearing wiud do nicely
doesnt take much work to get 1 hp per cu with these engines
type of cam really determins the total balance of the peak hp and tq..