Why did GM build 3 engines so close in CI 302, 305, and the 307? Just curious.

I asked this question on the "Ask GM" but was told it wasn't warranty related and wasn't allowed. But in the sticky it also says tough Tec questions. Guess it wasn't tough enough.

I just wanted to know why 3 motors.

 

The three motors all had different design intent.
The 302 is a racing monster. It was the one of the first engines designed by factory engineers for racing. I am told that a race team could disassemble tweak Port polish, balance the motor and it would dyno at the fly wheel almost 500 HP. GM listed the HP at 290 so it did not over shadow the SS 350 but the realality was if its stock form it could turn 7000 RPM at like 380 HP. The reason the 302 is 302” is because that was the max size for the Trans- AM race in the mid 60’s GM,Ford and Mopar all had a 302.
307 was an engine designed for low cost of manufacture. The low torque allowed for cheap cast iron parts without the risk of failure
305 was GMs quick answer to the emission problem. Because of emission low HP motor were the norm and the existing SBC engines where all overkill in design. Since how fast a car is based on HP vs weight and they could not have HP then they reduced weight as much as possible. The 305 is the red headed step child of the small block world.

 

Thanks Gorn! That was the lesson I needed. I new a little about the 302 but wasn't sure of the why on the other two.