Novaboy,
It takes a LOT] more than just headers and a 4 barrel to make an old inline 6 go fast. Especially a 230 CI.
To achieve a truly proportional increase in power you have to increase your compression and raise the HP RPM range. And these changes will be largely wasted if there isn't significant headwork along with the other changes. Because the stock 230/250/292 straight six head design sucks from a performance point of view, with the large boss in the center of the head.
To give you a point of reference regarding power, I went from a bone stock 230 to a 292 with some hop up goodies (larger cam, 4 barrel, long tube headers, .060 overbore, etc.). And there isn't a much improvement at all over the 230 through the first 2500 rpm. All in all I probably added 40 horsepower (maybe) over a stock 292.
-magic mike-
