John, et Listers,
I have scarcely had time to just read the postings of the last couple of
days let alone respond, but taken as a whole, I see a lot of good input
from a wide range of perspectives. While I wouldn't want the List to turn
into a forum for personal vendettas, I think we all need to have some
forbearance for those who have legitimate gripes and concerns to express
themselves. We are probably near the limit of what I would personally
consider appropriate, but I'm OK with most everything posted to the List so
far. It's real easy to hit the delete button with those messages that
don't, for whatever reason, interest us. IMHO of course.
Now, to the technical part of your posting. Just how do you use the
accelerometer? Do you actually drive 1/4 mi, 0-60, etc.? I presume not, but
instead it calculates the times and speeds based on your acceleration over
some arbitrary distance or time. As for the 30% SROD tranny, I presume this
means that fourth gear is 0.77 (reciprocal of 1.3). If this is correct,
then I would suggest going 30% higher in numerical rear end ratio. The
2.88s are good for high speed cruising; e.g., 75 mph at around 3125 rpm,
and if you went 30% higher to a rear end ratio of 2.88x1.3(or 2.88/0.77) =
3.74 (i.e., 3.73s) you would have the same result in fourth gear as 2.88s
with a 1:1 fourth gear toploader. I drove a Tiger with 2:88 gears and a
five speed with a similar top gear as your SROD and found it to be way too
tall to suit me, although it seemed to be OK with the owner. How OK would
depend a lot on how the motor is built; i.e., does it pull well down in the
low 2000 rpm range. I guess the competing issues as far as final (net in
top gear) drive ratio are throttle response, engine noise, gas economy, and
perhaps engine life.
My impression of the SROD, from discussions with Jim Barrett a while back,
is the gear spacings are way too big for a sports car. You can never get
nearly as much performance out of a motor if you have such big changes in
rpm between each shift. For performance (i.e., acceleration) you want to
keep the engine running as close to its peak horsepower rpm as possible.
Your car's average acceleration is directly related to the average
horsepower output of your motor between shifts. That's precisely why the
"close ratio" toploader was used on performance oriented cars like the
Tiger. On the other hand, the choice of close ratio gears limits the
flexibility of operation, especially with a highly tuned motor with a
narrow rpm operating range. Put another way, don't try running a close
ratio with 2.88s and a big overlap, high lift cam. You'll be replacing your
clutch every other month. On the other hand, this setup might be just the
ticket for running at Laguna Seca. The right solution just depends on how
you plan to use it. Nothing works best for every situation, although using
an automatic instead of a manual transmission might come close (not that
I'd suggest giving up the fun of shifting).
Any comments about the Torker manifold? Isn't this a single plane manifold
that gives up a lot in the lower rpm range? I'm not the expert on newer
manifold designs, but I've heard that some newer single plane designs are
much better in this regard. The conventional, if perhaps outdated wisdom,
is to use a dual plane for the street. Your 1/4 mi times and speeds seem
very modest considering the description of your motor. I'm just wondering
if the manifold is the problem. Or is it the SROD with the wide gears? Or both?
TTFN,
Bob
At 03:25 PM 4/30/99 +0000, johnc@nait.ab.ca wrote:
>
>Lets get back to some TIGER stuff:
>Jim B. stated a while back that he had purchased and accelerometer. I
>wonder what his results were with the 351/SROD. Has anybody else tried an
>accelerometer?
>How about posting your 0 - 60 time, 1/4 mile time and 1/4 mile speed?
>List your engine, trans. and gear ratio.
>The accelerometer says that my TIGER runs:
>0-60: 8.01 sec.
>1/4 mi: 16.00 sec. flat
>1/4 mi. speed 86 MPH
>I have a 289 with Holly 600, torker intake, 302 heads; 30% SROD Trans., and
>a 2:88 final ratio.
>
>I only borrowed the instrument and got to do 3 runs. It was addictive. I
>was sure that with practice I could shave these a fair bit.
>Also I need a better final drive. How do I calculate what ratio would be
>15% lower than 2:88?
>Godspeed
>Jc
>
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
|