Just a thought here; DV just released a Polyquad 4 valve discussion video. Now I realise the SBM is a 2 valve, but pick tidbits where you can. If you sink the exhaust valves about 0.100", the exhaust is almost closed when the intake opens and the inkake air/fuel skips over the exhaust valve head instead of some finding its way out the exhaust. Also 40° exhaust seats allow blowdown quicker in like manner to back cutting the intake valves. This helps reduce pumping losses as the piston rises on the exhaust stroke. If using headers it also increases the strength of the pulse tuning. Could help with tuning the EFI and keeping the O2 happy.
