I hope you've thought about the decrease in compression if you alter the combustion chamber shape. Lower compresion = lower performance. You'll need to find/make some domed pistons for your engine.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"
Funny thing is a lot of engines past and present have hemispherical combustion chambers it's just that Chrysler trademarked the term "Hemi". So you can think of it this way, a "Hemi" is to engines as a "Whopper" is to hamburgers.
Straight tubes suck, the beauty is in the bend.