Originally Posted by
Padgett
a) "even fire" means the cylinders fire 120 degrees apart (2 revs or 720 degrees in a full cycle). The CF firing order is 1-4-3-6-2-5 so banks are alternating. With a normal crank and a 90 degree block this would mean some cyls would fire 90 behind the last and others 150 degrees. By offsetting the crank journals 15 degrees positive on one bank and negative for the other you can make the firing sequence even.
So what you have is cyl on each bank firing exactly 240 degrees apart. This means you can tune the intake and exhaust ports for laminar flow to maximize the gozinta and gozouta (not as important with boost).
This generally means you have torque building to a peak and then tapering. Exactly what this curve looks like is what tuning is all about and why modern engines with VVT I&E can have such broad torque curves (90% of peak from 1800-6400 rpm). Without, just how peaky an engine is depends on how wild the cam and the intake and exhaust runner length.
If you really want to know the physics invold fond a copy of Harry Ricardo's "The High Speed Internal Combustion Engine". I have a 1958 edition but if you really want to understand the theory, that is where to start. Obert is OK but I like Ricardo better.
b) If you want a quiet exhaust you give it time to cool a bit and join the two banks about 30" from the head (why two CCs, you want to maximize exhaust heat since they do not work under about 600F). This is why any "interesting" V8s have an X or H pipe behind the trans (se also Helmholtz tubes).
However if you really want it to sound like a D jag or a Corvair on trombones then you need to keep true duals from the cats back. Use a single pipe or duals with a crossover and it won't sound nearly as pure.
c) They may be alternate firing plugs but I would be surprised (anyone have a picture of the combustion chamber, the ones in the service manual show a single plug four valve head) if they do not fire sequentially for emissions purposes rather than power. Usually there is a single sweet spot in the head for even flame propagation, probably between the two intakes and as near center of the combustion chamber as possible (not going to get into CVCC and such if possible but other designs usually have a CR in the 7-8:1 region) and if serious you index the plug so the gap faces the exhaust valve.
The current Hemi uses dual plugs but the second is to try to keep emissions down and not for power.
Enough for now.