[junglejustice]

400-plus (crank) horses from an NA 3.7 litre 24 valve Alfa V6 is no longer a mystery - its pretty much a foregone conclusion...! 12 valvers won't touch that in NA - not even close - you need the 24 valve setup at that point.

As far as the old "no substitute for cubic inches" argument; yes - this also holds true when you are talking big-bore Alfas (they really need the CCs!) With it however, comes commensurate risk - the heads won't seal and an increase to the combustion-dome, protrudes in to the water-jackets (even MORE so on a 12 valve head!)

At the same time, we're talking 10's of CCs - right? If you can't make the power off of 3.6, 3.65, or 3.7 litres, you're not going to make it off of 3.8 litres either, so why stretch it to say a 101, 102, 102.5, 103mm bore-size?

I know of properly built 3.45s even (still on "amateur" budgets), that smoke 3.8s built on similar budgets (but with less experience behind it...) If the basics are good, the thing will make power. Ports, compression, cams, valve-angles and most of all - mapping!