(wanted) Edelbrock 60177 or nicely worked RHS heads

Quench = prevention from detonation.

Open chamber heads are more susceptible to detonation. You can usually get more compression from a tight quench engine before it detonates as compared to a similar CR open chamber engine.

I've fought with a few 340's with X/J heads to get them to stop detonating. If I can help it, I prefer to run closed chamber heads. The last set of Ede heads I got were open chamber... not any more, after a few runs on a surfacer. :) Last engine I built was .005 out of the hole with a .039 gasket, pretty tight by most standards.

All good, make an informed decision.