you can see, we got close, but not quite into the 11's just yet.
While we beat our previous best ET by nearly a tenth, the mile per
hour was down slightly. What was interesting to see was that our
sixty foot improved by almost a full tenth, presumably due to the
drag shocks, and possibly the low-end torque increase of the exhaust.
Our best run this time out was a [email protected], on a 1.64 sixty foot
time. Last month we ran a [email protected] on a 1.73 sixty foot. The
dramatic improvement in the short time should have yielded more
than one tenth off the ET, however it didn't. The car was actually
exactly one tenth faster at the eighth mile and the 990 ft, but
somewhere after that at the very top end we lost a couple hundredths.
We would have hoped for this run to be a 12.03 at minimum.
We ended up running very consistent numbers this time out. A handful
of 12.0's and 1.6X sixty foots. Ironically the 12.05 was not the
best run of the day. On another run we nailed a 1.65 sixty foot,
and had a 7.67 eight-mile at 93.7 mph, but then missed fourth gear...!
So far that eight-mile run is the fastest the car has put down,
by a half-tenth and two mph!
The drag shocks worked, no doubt about it. The exhaust system is
more efficient than expected. It is robbing no more than a tenth,
perhaps less, and one mph at the top end. However the eighth mile
speed has increased slightly, so overall it may be a wash. Next
time out we'll make a pass without the pipes and see what happens.
Last months dyno results are perplexing. We picked up about 26 horsepower
from our baseline pull. So it would be expected that we'd see an
improvement in ET and mile per hour, on top of, the gains
from the improved sixty foots. However we didn't really notice this.
We gained .07 to .09 better sixty foots, and our ET showed the same
reduction. What happened to the extra ponies? The only theory we
have to offer is that the power gains are being offset by the exhaust
system. We did have to jet the carb down a few sizes from the optimal
jetting obtained on the dyno. This is consistent with putting on
an exhaust system, as it tends to slightly richen up the air/fuel
the 11's ?
couple people has warned us that running 11's means breaking parts.
It takes a 3200lb car roughly 350 rear-wheel horsepower to run high
11's, assuming all the power is getting to the ground. Unfortunately
that much power is beyond the threshold of most clutches, transmissions,
rearends, and axles. You can probably get away with stressing those
parts for a short time, but eventually they'll fatigue and break.
Therefore you see very few cars running stock drivetrain components
beyond the 12's. We've known for a while that we'd need to upgrade
our stock T5 and also the 8" rear end. So far we'd been luck
by crossing our fingers and biding our time. Well not this time....
After making the 12.05 pass, we immediately rolled to the line for
one last pass for the day. Having already made eleven passes, each
with 4500+ rpm launches, we should have known better than to hot
lap the car and make another pass. This time, instead of another
1.6 sixty foot, the 5000 rpm launch resulted in a dull "thud!".
We rolled the car back to the pits, checked the axles and u-joints,
and found no problems...so we thought.
thing is that we drove the car home, 75 miles, without realizing
an axle was actually broken.
So we've found the limits of stock 28 spline axles; somewhere around
low 12's and a few 5000 rpm dumps. We're still surprised that the
8" differential itself is still holding strong. So is the T5,
but it's not subjected to power shifting.
Since 8" Fords cannot be upgraded to larger 31 spline axles,
we picked up a couple 28 spline stockers from a wrecking yard. Once
again, we'll roll to the line with our fingers crossed, but don't
be surprised if you read about a 9" buildup in the near future!
axles break right where the splines end. It's also the drivers
side that tends to break due to how the ring and pinion distribute
Getting the broken piece out of the differential can be a
challenge. This one was stuck pretty good.
wanting to disassemble the entire third-member, the option
was to drill and tap the broken piece, then pull it out using
a large socket as a slide hammer against the head of a long
8" and 9" axles come in two styles. 1966 and earlier
cars have axles which taper severely in the center of the
shaft (circled section.) Starting in 1967 the axles were beefed
up, with virtually no taper. We picked up two of the stronger
ones, for $20 a piece at a wrecking yard.