After at least 200+ dyno runs over the past 30-something years, I've found that most header systems only increase an engine's power at RPM ranges that rarely, if ever get used on the street- - - - -unless you're in the habit of collecting speeding and/or reckless driving tickets. A good set of rams' horn cast iron exhaust manifolds will equal (or outperform) headers over at least 80% of the usable speeds most street engines see. However, headers do excel at two things- - - - -raising under hood temperatures and roasting spark plug wires. That's particularly true once the thin steel flanges most headers are made with warp a little and start to leak exhaust gas. If you build your own equal-length headers with flanges at least 1/2 inch thick, the leaks don't happen as often.
Jerry
