The aluminum is more forgiving than iron to start with. The fast burn chamber is more efficient and needs less timing over an open type chamber. I'd think the KRE head would be more forgiving over an iron head. But to know how prone you are to detonation means your combo has to be shown. N/A or turbo? All engines are different though the norm seems to be 30 to 34 total timing for the KRE heads as posted by quite a few owners. Advancing the timing beyond that yielded no more power or they made less.
You say you had 28-30 with the iron heads and now 20 with the KRE's? Total timing, no vacuum advance connected and it is coming in at what rpm?
Are you running vac advance? Ported or Manifold source?
Stock distributor?
Base timing? at what idle rpm?
List your engine specs, bore, stroke, piston, chamber size, head gasket thickness, cam specs.
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68 Firebird
Are you running with the wind or breaking it?
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