Hi Ray,
Just something from my "Car maker" experience. The 2 inner manifold pipes would normally come from further away - not the nearest - holes in the plenum. Makes the inlet tracts nearer to the same length as those to the outer cylinders. In fact a lot of work went into making the inlet tracts the SAME length to eliminate differences in "resonances": I.E. 2 outer cylinders with longer tracts could at some resonant point in the rev range take ALL the mixture effectively, leaving a transient depression (or pressure!) for when the next inlet valve opened, which if an inner cylinder with shorter tract length was not resonating and unable to cope with the different manifold pressure... so not getting the right mixture and causing a flat spot at the resonant engine speed... instead of the expected "boost".
Simply, when all the inlet tracts are the same length there is only one "potentially problematic" resonant speed to manage especially - instead of 2, when there are 2 sets of inlet tract length.
Longer tracts also resonate at a lower speed, - usually within an engine's rev range, but shorter tracts sometimes resonate above the max engine speed.
Racers use resonances to get extra power. The "common man" driving his mass produced car doesn't want to feel a resonance that can give a sudden surge of power, but sometimes these are tuned to suit other factors. E.g. if an engine is on an automatic transmission that normally runs the engine at a fixed rpm (max. torque rpm). then the inlet tract length (and maybe exhaust lengths) will be tuned to resonate at that length to get the natural power boost available.
For a "bench idling engine" it matters not a jot - except to passing "rivet counters".
I like the clear pipes? What material have you used? - My supplier doesn't do clear metal...
Ken
