Turbo header design

[Greg Hermann]

>
>    Care to elaborate on this a little? Are we talking about crank vibration
>(hamonic balancer/flywheel) or something else over my head? Also, a Chevy
>V-8 fires every 90 degrees of crank rotation. How does a flat crank V-8
>fire? Every 180 degrees would make sense, but then it would take 4 turns of
>the crank to hit all 8?! I am so confused......

Secondary vibration, due to the fact that piston accelerations are
different at the top and bottom of the stroke due to con rod angularity. A
four cylinder has an up and down shafing force at twice crank speed (which
is sometimes countered fairly well with two "balance shafts" counter
rotating at twice crank speed.) A flat crank V-8 is like two fours.  Too
late at night to try to describe the shaking which results. A 90 degree
crank V-8 is not in perfect primary and secondary balance, as Gary claimed,
but it is close. An in line 6 has inherently PERFECT primary and secondary
balance. Only reason for crank sounterweights inna 6 is to reduce bending
stress in the crank and block.

Tertiary balance is another matter--it has to do with connecting rod mass
distribution, and is generally accepted as being not too significant.
Efforts to obtain/improve it explain the long tangs sometimes seen
projecting above the small end on a connecting rod, and also the rather
large pads often seen on the bottom of the big and cap of rods.

Why the Super speedway headers sound so neat (as also did Ford Mark IV's
and Ford's four -cam Indy V-8's) is cause the individual exhaust pulses
into each of their two collectors are EVENLY SPACED (180 crank degrees
apart) , from whence the name. You cannot get that on a V-8 with a 90
degree crank without crossing tubes from side to side (bank to bank) to the
collectors. You do get it with a four into one header on each bank (without
crossovers) on a V-8 with a flat crank.

Regards, Greg