Originally posted by giddyup306:
If you look at the 3l heads and the 2.5 heads side by side, you'll notice that there is 2 "bumps" between the valves. I would recomend taking material from there. It will lower compression and recude the possibility of detonation.



Bad idea. Those are there to promote swirl which = better cylinder filling. You'll loose a ton of low RPM torque/HP if they're removed.

You're much better off removing material from the outer edge of the combustion chamber (I.E. laying back the chamber walls) on a 2.5 head to unshroud the valves for the larger 3L bore. But that's only iff you want to lower the compression ratio, which is really the only remaining draw to perform a hybrid over a straight 3L...

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