As I was reading through a bunch of forums, I keep coming across rod myths and misconceptions, and mass confussion I'm going to try to help out and others should share their knowledge also.

1. Rod length strokes or adds cubic inches: TOTALLY WRONG
Rod length has nothing to do with stroking or cubic inches
the original 400 had 5.565 rods. You can use 6" rods in the
same engine and still have a 400. The part that rod length
plays on a engine is thrust and angle, also dwell but we'll
get to that. When GM went to the 400, instead of changing
the pin bore (compression height) they shortened the rods
which really wasn't a good idea because of the thrust and
angle at which the rod worked put a stress on the bore
and wore it out in no time. You need a good rod to stroke
ratio. The longer the rod the less stress and more effient
it is. With long strokes and standard deck heights, rod
lenght all too often get compromised. Example--A stock 400
has a ration of 1.48:1 and it wears bores quick. If you were
to stroke a chevy block to a 4" stroke and use a 6" rod, you
would only have a L/R ratio of 1.50:1 which is still short.
But you can't add any more rod length because your left
with a compression height (distance from the centerline of
the wrist pin to the crown of the piston) of about one inch
and three rings have to fit in that area. In fact on that
setup the piston pin is into the oil ring. A 350 with a stock
5.7 rod has a L/R of 1.64:1. Always use the longest rod
possible.


2. A long rod engine reduces detonation. WRONG
A long rod actually has more dwell time at TDC and
Therefore the air fuel mixture is warmed up longer, giving
the charge a better chance to detonate. A short rod engine
doesn't get a chance to dwell because of its acute angle and
is jerked around.


3. Longer rods give more compression. WRONG
The longer rod doesn't push the piston up the bore any
further, just the pin location changes.


4. A short rod engine makes more low end torque. NEVER PROVEN
Even if it does, bore wear off sets it.

ON A FINAL NOTE:

ONLY BORE SIZE AND CRANK THROW ADDS CUBES.