302 cubes for Suburbia

[1project2many]

There are many after market replacements that differentiate between the 1/2 ton and 3/4 ton exhausts. Magnaflow, Walker and Catco are just 3.

I'll look again at Walker. Maybe I just missed it. Local exhaust guy is Magnaflow dealer so maybe I can get a good price on an expensive brand.

All else equal the small bore 305 should be MORE detonation resistant than the larger 4" bore. I might be tempted to work from an L30 calibration.

I've never really investigated the 305's issues so I can't tell you why it's more likely to knock. It would seem like head design is the key. The L30 represented a great chance to fix any problems inherent in the older heads yet the tuning tables indicate there are still problems.

Main spark table, knock attack, and knock retard rate comparisons are below. Yes, there's a bit more spark advance on the bottom end but at the top it's a whole different picture. Not only is timing lower on the smaller bore, but GM is really quick to remove advance if knock occurs and slow to return it. This is typical of the 305 although it's less pronounced here than older engines.