Petersen Pub. Co. used to print a "Hot Rod Annual" which I tried to collect and somewhere around 1971 or so there was an extensive set of dyno runs by Iskederian Eng. on modifying the SBC 350. They got it up to over 480 H.P. without nitrous or any forced induction but in terms of (HP/$) the simple change of the stock cam for a mild Isky cam gave the most increase of about 63 HP for the price of a reground cam. For many years I was hooked on the idea that all you had to do was rebuild a 350 and change the cam. However, when you read the dyno charts carefully you can see that the low rpm torque drops off considerably when the cam is selected for more HP in the 4000 rpm range. That is why I now look at the low rpm torque since that will be the operating range when cruising in 4th gear OD. I just found the old article and the HP gain was 62.3 HP for the $55 Isky 280-H cam with a peak HP (I assume at the flywheel since their stock baseline was 293.7 HP at 4000 rpm.) With the only change being to the 280-H cam they got 356.0 HP at 5500 rpm. For comparison, the stock cam produced 170.8 HP at 2500 rpm but with the 280-H they got 158.7 HP at 2500 rpm. Using their old price that was (62.3 HP/$55)=1.13 HP/$. Probably a similar cam can be bought for even less today from Speedway, but of course that is the old way of measuring the HP at the flywheel and it is obvious that more HP at higher rpm degrades the low rpm HP. This is just playing with numbers but you said (HP/$). Overall I would agree with lt1s10 that adding a Roots-type blower would be the best way to add a lot of HP, but then what about overheating and crank bearings?
Don Shillady
Retired Scientist/teen rodder
