awhile during the early years of the BB, simon anthony and big thanks to peter for setting up the magnaflow alfa dyno days at his facility.Good points, although I won't rule out the street-cred derived from a cool looking engine. In terms of effectiveness headers can offer incremental horsepower advantages. You may see some small benefit on a stock engine but where these kinds of incremental contributing factors come into play is when you are building a fully-built motor. With the right combinations of head-work, cams, high-comp pistons, ignition, carb mods, lightweight flywheel, balanced bottom end, etc., etc. you can build a very decent 160-170hp 2 liter Alfa Nord engine that will be a real blast to drive. It won't be a state-of-the-art race engine but you'll nonetheless have a very satisfying increase in hp that will nonetheless run quite happily on pump gas and return 21-22mpg.
Several years ago I think George Willet commented that slightly modified stock, cast-iron headers were entirely good---up to about 140-150hp when, along with other required mods, proper headers came into play. This seems about right to me.
Well, we're all lookin' for that secret sauce ingredient!
somebody that was keeping track said it was the highest powered nord of the day. spica on stock manifold, 133whp depending on how you want to calculated the losses 155 to 165hp at the crank. note the car car was not dialed in yet as you can see by the A/F readings. Ive later added the SS exhaust since the vid.
you can hear how much smoother the cast irons sound over the tubular headers of the others
dyno graph, off the shelf specs and my own secret sauce porting. here: