Originally Posted by Ed ke6bnl
My 72 el Camino is using oil like the Valdez in Alaska. It was a no history 350 motor from someones 67 nova was good for several years, I still have the maybe original 307 that was
in the truck when I got it
and I have the chance to get another 76 el Camino 305 for the motor,to swap into my 72. Is one with the 305 versus the 307
better then the other. Fuel economy is now an issue not when I first put the 35o in a few years back. Your thoughts thanks Ed
These can be though of as the 307 being a 283 stroked with a 327 crank and the 305 as a debored 350.
The 305 has a 3.48 stroke and the 307 a 3.25 stroke. The difference probably isn't noticeable. Both engines were an attempt in time to put the torque peak at a lower RPM on a smaller engine to give it more mid RPM punch without resorting to more displacement.
There is no guarantee that a smaller engine will get better gas mileage in a larger vehicle. It takes X amount of power to make it go. Whether that power is coming out of a 305, 307 or 350 it's the same. The difference is how much throttle opening is used, the smaller the engine the more throttle opening used at any given RPM.
An example, my S15 originally had a 151 Iron Duke and a 5 speed. It now has a 350 with a 4 speed auto, overall the fuel consumption hasn't changed much. Unless I get on it.