Hi snowy15,
In 1968 auto manufactures quoted Gross HP ratings for their engines. These numbers were obtained on an engine dyno with the engine stripped of accessories and running open headers. Not real world.
In 1972 the industry went to a Net HP system wereby HP was quoted with the engine equiped as installed in the standard car (no air, power steering, etc). This system was adopted as a result of false advertising complaints by many consumer advocate groups.
To answer your question, in 1968 HP (gross) was quoted as 115 @ 3800rpm. In 1972 HP (net) was quoted as 91 @ 4000. Since net HP is what is quoted today, the 91HP rating is the number to use as a baseline.
Here are a couple of interesting comps (Gross / Net)
65 HIPO 289 - 271 / 176
70 Boss 302 - 290 / 209
Rear wheel HP is a more meaninful value in my mind. This number can be obtained for any car, at any time, by taking it to your local dyno shop and putting it on the machine. This is not cheap. But it is the way to verify the value of your mods. A 200 I6 in good tune will deliver approx 65 - 67 HP at he rear wheels. The reduction from net HP represents the power absorbed by the drive train (trans, drive line and rear end). In this regard a stick is more efficient than the automatic and the condition of the rear is meaningful. The rear end gear ratio is not a factor in the number.
B4 you start modifying your car get a copy of the Ford 6 Performance Handbook (falconperformance.sundog.net). This is a must read.
Enjoy the trip - Steve
