best mods for the h22a is a tuned program for the engine (requires some dyno time), a light flywheel, and lsd. Those 3 things will do more to lower your ET at the track than anything else you could possibly want. After that, its time to start basic mods (although, i wouldnt, id start off a little differently if i could). Once you do the almost required intake/header/exhaust (all 3 are personal preference, they just help your engine breathe a little better), its time for the REAL engine stuff MWAHAHAHAHAHA!!!
Im about to start getting really in depth just in case someone else is reading that is curious about an NA build for a prelude.
A lot of the parts listed are gonna be OE honda parts and itd be easier to get a lot of these parts used. Only thing i can say is this is gonna take some work.
H23 Crank (95mm stroke)
Modified F23 (141mm) rods (modified for a larger wrist pin)
87.25mm Type S pistons
Adjustable Cam Gears
440cc injectors
H24x Rocket Cams Package (Includes Cams, Springs and Retainers)
Those things should be good for about 220-230whp depending on your tuner (because tuning WILL BE REQUIRED!). Basically whats going on is youre increasing your overall displacement, and your compression ratio while adding a fat cam. Couple all those things with a good tuner and you have potential for some really good power.
Pretty good package of stuff for an engine build, and dont be confused i left stuff like head gaskets, piston rings, bearings, blah blah, so while i only listed about $2500 bucks in parts, the build will probably cost about $4000, assuming you have someone else do it.
Once you get to this point its really more of a fine tuning process in getting everything out of your build.