|Getting a '97 Corvette to run in the 12s
Title: C5 Buildup
"We wanted the Mongoose to be a Mongoose 400. Astonishingly, we made
it there with a Nology ignition system."
"The Nology ignition whipped up the big drums
on the dynojet to the tune of 11 more horsepower."
"Our theory was that, with only 25 degrees of total timing on the LS1,
the Nology short-burn time and precise firing was a good match for the
for '98 Corvette LS1
|| Part Number
||From $ 350
|Silverstone Spark Plugs
||From $ 7.95 ea
Several months ago, we left you at 330 horsepower and 332 lb-ft of torque
at the rear wheels. This month, we return with 340 horsepower and 352 lb-ft
of torque! That 10 horsepower and 20 lb-ft of torque was no easy task. Along
with our dyno numbers, we gave the Mongoose a full complement of track tests
at DeSoto Speedway in Bradenton, Florida. With several trips to the track,
we never did find ideal weather or track conditions, but our efforts were
rewarded with better elapsed times and trap speeds. Here are the results.
We wanted to take advantage of the increased breathing potential we created
with the cylinder head work, Power Pak and Tri Flo Exhaust (see the February
issue). This meant we had to come up with a camshaft to match our earlier
enhancements. This quest started with a desperate search for a camshaft core.
No luck! Unless you're under the corporate roof of Chevrolet you are not
getting a cam core! We had to resort to having the stock LS1 cam reground.
There's one very big limitation to a regrind. You have to make sure you don't
grind past the factory induction hardening. If you do, the camshaft will
go soft in short order - instant junk.
We first chose a camshaft profile that's shown great success in the traditional
fuel-injected smallblocks. The actual installation was pretty easy going.
A really neat feature of the LS1 is that neither the intake or cylinder heads
have to be removed for the installation of a new camshaft. With the rocker
arms removed, tension is released and the hydraulic roller lifters will move
up into a holder when the camshaft is rotated. The camshaft will slide right
out. The tough part is removing the steering rack, which has to be removed
to get the front crankshaft balancer off.
This first cam profile left a lot to be desired. The dyno testing after the
cam installation showed a lousy three-horsepower gain in exchange for a loss
of 40 lb-ft of torque. Back to the drawing board. This time we enlisted the
help of Myron Cottrell at TPI Specialties.
We've seen some pretty incredible horsepower and torque numbers from camshaft
development at TPIS. After a long discussion with Myron, we decided on a
profile with less duration and a little more lift on the exhaust side. This
was an educational project, and we had to forget everything we knew about
the traditional small-block Chevy. With the LS1, there's a very fine line
between finding torque and not losing horsepower, or finding horsepower and
not losing torque. At this point in our experiment, it seems that lift is
the key. Also, the engine seems very sensitive to duration.
During the wait for our second camshaft, we were back on the dyno, trying
all sorts of tricks. Pro Auto Tech had come up with a set of low resistance,
high-temp ignition wires and racing spark plugs that kept the coils cooler
under those black rocker covers. They showed a slight increase in the dyno
numbers. More important, we found that we could make several more dyno runs
without a drop-off of power from the hot coils. Pro Auto Tech also developed
an adjustable fuel-pressure regulator. This allowed us to tune the air/fuel
mixture to exactly 13.0:1. The wires and the tuning ability of the fuel-pressure
regulator provided up to six more horsepower in conjunction with the Power
Pak. This adjustable fuel-pressure regulator proved to be very beneficial
at the track, where we could make adjustments to the fuel delivery to adjust
for the high humidity.
We could hardly wait to get back on the Dynojet dyno after our second cam
installation. This one felt really torquey. Catching second gear right before
the 6250 rpm rev limiter cocked our Mongoose sideways, our tires screamed
out a cry of punishment. The dynojet numbers confirmed our driving experience.
This camshaft gave us back all the torque we'd lost with the first camshaft,
plus almost 20 lb-ft more.
We were now over 340 lb-ft of torque, and real close to 340 horsepower
on the chassis dyno, which equates to approximately 400 horsepower at the
crank. We wanted the Mongoose to be a Mongoose 400. Astonishingly, we made
it there with a Nology ignition system. With a coil for each cylinder, you
wouldn't think the ignition system would be a weak link - but it was, indeed.
The Nology wires have a built-in capacitor that provides a very quick and
intense spark. With past testing of the Nology ignition system on earlier
L98 Corvettes, we found around six horsepower at the rear wheels by retarding
timing a few degrees. The Nology ignition whipped up the big drums on the
dynojet to the tune of 11 more horsepower. Our theory was that, with only
25 degrees of total timing on the LS1, the Nology short-burn time and precise
firing was a good match for the LS1.
We now had 340 horsepower and 352 lb-ft of torque. Plugging our new dyno
numbers into our trusty Drag Race Analyzer software showed we should be able
to turn 12.50 at over 110 mph - if the tires would hook up and if the air
was good. If ... if .... Well, it doesn't cost anything to dream! Making
power on the dyno is one thing, getting it to perform with the car is another.
We hope to be in the low 12s in the next installment. Keep in mind that were
going to do this with stock displacement - the Malletts are doing 11.99 with
a bigger engine.