bigjoe1 wrote:Here is a true story-- I build quite a few 383 Chevy engines, I usually use 6 inch rods because I like the light pistons. But, once when there were no 6 inch rods available, I put my regular 383 combo togeter with the shorter 5.7 rods. The engine was down everywhere about 15 to 20 HP, and 15 to 20 pounds of torque. That was the only time I used the 5.7 rods, and after that, I will never use them again.
JOE SHERMAN RACING ENGINES
another true story->
around 1991 to 1993+ time period
i Ported different pairs of SBC #041x castings 165 CC Legal limit
with varying Port velocities (epoxy shapes)
for a SS/I 4-speed Camaro
unknown to me,
they used a 6.250 C-C rod with the 1st pair i Ported.
The Pitot Probe velocity was fast , and i was experimenting with
how fast you could push port speeds in various locations.
Port CC's were between 160 to 162 cc well safe of 165 Limit
the SS/I Car ran as fast as 9.69 ET around 18 years ago
and always between low 9.70's to low 9.80's w/6.250 Rod
set the SS/I Record like it was
since he was very fast for its time,
they decided to make it 100% Legal switching to 5.7" Rods C-C
..from that point it slowed down a solid Tenth ET or more
it became a high 9.80's to high 9.90's Car
i ported another pair with barely any epoxy in Ports
slowing velocity as much as i could,
kept Port volume on ragged edge of 165 CC limit ( 164 to 165)
with a Class A Burette
ran a few high 9.70's to low 9.80's
after 2years, NHRA reset Record...slower,
so he set the SS/I Record , but to a slower ET
i think he reset the record a 3rd time in SS/I later on
won Class at Indy 1993
its interesting that the 2009 SS/I Record is only a 9.93
never again did it run any 9.69 or any low 9.70's !
like it did with 6.250 C-C Rod
this was approx 575 HP @ 7300 w/6.250
556's HP @ 7200-7300 with 5.7 Rods
down the DragStrip, since this was a 4-speed manual Trans
with 5.83 gears 3.08 1st
the RPM/SEC acceleration rates were approx->
1st Gear= 4300 RPM/SEC Avg
2nd Gear= 2000 RPM/SEC Avg
3rd Gear= 1070 RPM/SEC Avg
4th Gear= 560 RPM/SEC Avg
as you can see, the RPM/SEC rate is very fast,
coupled with small port volume head that was edge of too fast,
seemed to respond a lot to Rod Length changes.
--------------------------
if that were a 2-spd Powerglide Car, the avg RPM/SEC would have been
a bunch overall slower and not tax the Rod Length / Head CC combination
likewise if there were no 165 Cc rule and
you just built the same CID shortblock with a modern head
the Rod length effects becomes less
to where some say Rod Length doesn't matter at all !
then you look at Smokey's Era where you used
old Double-Camel_Hump Heads and old #292 Turbo Heads
with relatively small port volumes and possible very hi , too fast
local velocities causing CHOKE situations,
then you can see why Smokey preached long rods all day long !