It's not just the 16" vs 17" wheels. The base ignition timing is dialed back on the '79 Special and it has a different vacuum advance curve. It might have a different mechanical advance curve and/or total advance numbers but I'd have to look it up. There have also been confirmed stories of larger carburetor air and fuel jets from the factory in the '78 than the '79.
So, yeah, if the only difference was the wheel diameter then the '79 Special should blow the side covers off the '78 Standard but it doesn't because they reined it in a little. The slight additional mechanical advantage from the 16" wheel allowed the slightly detuned '79 engine to roughly equal the performance of the higher tuned '78 engine with its 17" wheel without exceeding it so the owners and the EPA were both happy.
So, yeah, if the only difference was the wheel diameter then the '79 Special should blow the side covers off the '78 Standard but it doesn't because they reined it in a little. The slight additional mechanical advantage from the 16" wheel allowed the slightly detuned '79 engine to roughly equal the performance of the higher tuned '78 engine with its 17" wheel without exceeding it so the owners and the EPA were both happy.
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