How? Look at the specs: its the same stroke but bored 15% bigger. 10.5:1 compared to 8:1 brought the HP up but look at the torque of a 318 compared to a 273 of any flavor sans D code. Im telling you, that "S" was a different car with that 318 block. I even used the 273/4 cam that was mismatched to the compression of the teen. Your results may vary..
