[OA5599]

Chrysler? 225ci Slant-six or 363 Big Block V-8. The 318 wanted premium fuel and underperformed.

Probably just a typo but Chrysler never made a 363. Did you mean the ubiquitous 383 big block? Or the rare 361 big block or the somewhat more common small block 360?

As for the 318, it underperformed because it was a low compression base small block V8 with a 2bbl carb. Premium fuel would not help a 318 because it was never built with high enough compression that it would ping without premium fuel. Now it's bigger brother 340 four barrel or six pack on the other hand...

[Dr. Sivana]

I meant the 383 in the 1965 Chrysler 300. I understand there was a later 383 that was a different design, but I had no experience with it.

[Dr. Sivana]

Premium fuel would not help a 318 because it was never built with high enough compression that it would ping without premium fuel.

I had a '79 Dodge Diplomat and an '89 Chrysler 5th Avenue (almost the same car! the '89 was the last Mopar automotive V-8) for many year. If you didn't give it premium, it would knock. Maybe the pre-smog control ones were set differently.