Some good points here. I'd agree with madkaw though, you can do enough to this car with head work and carbs. I don't know the 260Z as much, but a few posters on various Z boards have taken a modded E88 (shaved, larger valves, notched piston bores) or N42 (already larger valves, but shaved and notched) on a stock bore L24. You'd want a hotter cam and minimally a refreshed (if not bored) set of SUs. Slap in a better rear end (3.90 or 4.11) and you'll have a nice speedster. Now, depending on how "hot" you make the head / cam, I've seen "claims" ofanywhere from 14.5 to 15.5 seconds in the 1/4 mile. I put claim in quotes as I've not seen hard proof of the times, but 160 rwhp in a 2,300 lb. car is going to be zippy. Check out Classic Motorsports 240Z - essentially a stock L24 with a Sunbelt Performance head that generated 200HP at the crank (roughly 170 at the wheels) - certainly that car boogies, likely more than enough to satisfy most tastes. Otherwise, I'd go with Carl - buy a modern used car like a Honda S2000. You can get one for $15K or less and it will perform better than most anything you could do to a 260Z (short of a L28ET, but still requires some mods IMHO). I fret over this quite a bit as I have thought about bumping the power in my Z for years. Yet, I own a 2000 Lexus GS400 (300HP V8) that would smoke anything I could do to it on my budget - so why bother? These cars are wonderful time capsules that are meant to be enjoyed as they once were. If you have the scratch, anything can be done. Head over to Youtube and check out "Turbo240Z" (heavily modded L28ET) or "ZRedBaron" (3.1L stroker) and you'll get an idea. Bring your wallet.