Hotrodden the Predator Part 2 of 3

All across this nation, at tracks and in backyards,
classes to race the new Harbor Freight, 212cc,
Predator motors are forming. In part 1, we discussed ways to improve the power and made some
changes, and from what I saw while switching from
gas to alky, The Predator showed a great deal of
potential. When I increased the lift on the stock cam
by using 1.3 ratio rockers and, with Dr.Dyno’s help
assisted by my air fuel gauge, I was able to increase
horsepower from 6.5 at 3600 rpm’s , as stated by
the manufacture to 12.13 horsepower at 4800 rpm’s
. The cost per horsepower ratio was just right for
a “PoBoy” cloner’s wallet. You might even be able
to take the family out to dinner and still be a hero
at your local track or in your backyard this weekend, providing you didn’t break any rules with these
modifications. And if gas is your preferred fuel, you
can expect about 10.56 horsepower.
So you go out and buy a 6.5 horsepower
Predator on sale for $99. You take out the governor, install an open header and racing air filter, and
then you rejet the carburetor to run your favorite
pump gas. Boy, does she sound sweet now. Then
you go to the local track where 15 “good ole boys”
with Predators are just waiting for a newbie like you.
You haven’t raced in years but still remember how
to setup that old chassis that’s been hanging in the
garage for 10 years. With a fresh set of tires you
prepare to do battle and that old familiar knot in your
stomach starts from all the excitement as you line
up on the grid in 7th position. Your 4th on the inside
hugging the bumper of the guy in front of you and
the green flag drops. But before you can make 1 lap,
you find yourself in last place. What a bummer.
So after being lapped by most of the field, except
for the other newbie, who you did manage to pass
for a very disappointing 14th place, you walk through the
pits scratching your head and seeking answers as to what
the other guys and gals are doing that made them so much
faster. And yes, there were 2 girls in the field and they both
beat you. But then, you see their dads and you know why.
With trailers, setups, lights and tools all over the place, you
know these proud dads are members of the “PoBoy’s with
Greasy Nails” club. Oh boy! This is NOT going to be easy.
Now you’re heading home with your brain just whirling with
emotion and ideas as you try to figure out what to do about
next weekend. After reading an article by Sneaks about
race prepping your Predator a light goes on and you say,
“Hey”, I can do this.
So our weekend warrior sets out to do some head
work, change some jets again, advance the timing with a
new billet flywheel, install a new thinner head gasket, add
a little “white lightning” and with some assembly lube you
just know you got it right this time. The Predator fires up and
comes to life with a much deeper voice this time. After a 15
minute break-in you can’t help but notice how much cooler
the motor is running on the methanol. The throttle response
is sharp and crisp. You know this motor means business
now because the cold, sweat is dripping off the carburetor
as you run it through a few rev cycles. You’re ready this
time for some revenge.
All that puts a big smile on the face of our weekend warrior as he drives back at his local track. This time
he beats half the field and even manages to lap that “PoBoy” newbie from last week. And yes, he even beats one
of the girls. Hot Dog ! Now, that’s rewarding and a ton of
fun. That’s where we are with “Hotrodden” this Predator.
We have gone from 6.5 horsepower at 3600 rpms, to 12.13
horsepower at 4800 rpms without removing the side cover
or getting into the bottom end.
To recap, our test Predator has had the governor
removed but still has the stock piston and rod. It has a race
prepared head with 1.3 ratio rockers, stainless steel stock
size valves, 26 pound valve springs with a split keeper retaining system, open exhaust, rejetted carburetor, K&N airfilter, 8 degree advanced ignition timing, and a new billet
flywheel . And it will still start on the second pull. The cost to
almost double the horsepower was just over $100.00 and
a weekend of greasy fingernails. That comes to around
$250-$300 for an alky burning, torque monster. But in this
good old boy’s mind, we don’t have a real racing motor yet.
Now that I’m reasonably certain the Predator block, castings, and innards can handle this type of abuse and stress,
its time to make an actual “stock appearing” racing motor,
without breaking the bank. This is my “PoBoy’s” recipe for
being competitive with the top Predator runners. We now
have a good platform to build our budget friendly weekend hobby motor. Our goal this time will be to break the 15
horsepower barrier. That seems to be the magic number
that can make you competitive in “stock appearing” Predator classes. We have gone from 3600 to 5800 rpm’s and
I think our base motor will handle more and still be reliable. I’m thinking a target of 7000 maximum rpm’s would
be reasonable. In order to do this I’m thinking its time for
a racing camshaft, rod, and carburetor upgrade. Keep in
mind the size of your track will determine which cam is best.
You may want to get advice from your favorite dealer on
this. And check with your local rules because many tracks
have lift limits. For my test Predator, I want more torque and
stay around 6500 rpm’s for reliability. I have decided that an
Isky “Black Mamba” cam made just for the Predator has the
specifications I’m looking for. There are others that will work
great and it’s not illegal to pit next to the top runners and do
a lot of listening.
With all the extra rpm’s and improved breathing, the
next upgrade has to be the carburetor. The choices here are
many and your local rules will limit your selection. It’s also
important to buy one from a dealer who knows your location. These blueprinted carburetors come with jets already
installed and your track elevation will make a difference in
tuning them. Our rules say any stock body clone or Honda
carburetor. My test Predator will try a Dover SA, which is
the big brother to the “Holy Moses”. And the NRracing ,”SA
foot pounds @ 2000rpm’s. That’s an increase of 2.55
horsepower and 1.11 foot pounds of torque. But the
torque is now peaking at 2000 rpm’s instead of 2200.
More torque at a lower rpm range? That sounds really good to me. The new cam, carburetor, and rod
are going to cost a bit over $200. That’s a grand total
of about $500-$550, depending on what deals you
extreme”. Both are extreme bored carburetors.
To hold all this extra “POP” we’re creating, a
better rod will be needed. This Arc has a Predator rod
with a replaceable bearing shell and oil dipper that
will improve bearing lubrication. That will be needed
for an occasional burst to 7 grand when you hit that
slick spot. Putting it all together is something any
weekend mechanic can handle. A good tip here is
to use your racing oil and not assembly lube/grease
on the rod bearing assembly. Too much assembly
grease can get forced into the rod oil passage and
actually block initial startup lubrication until it melts.
Now that all the new parts are installed, it’s
time to make an appointment with Dr. Dyno and get
the truth. After a 30 minute warm up, break in and
air/ fuel adjustment, we are ready for “Hammer Down
Time”. The Predator went wide open throttle until
6600 rpm’s was achieved. The peak horsepower was
14.68 @ 5200 rpm’s. And peak torque was 17.14
can find. This build has the potential for even bigger
gains. All those horses and the compression is still
in the low range. Sounds like maybe a part 3 brewing here. And just by changing the carburetor you
can switch from alcohol back to low octane pump gas
and put the Predator back on the lawn tractor. You
best tell the wife first. Things could get ugly next time
you don’t get the lawn mowed in time, NASCAR is
on, and she gets impatient. I still miss that garden,
had to repair the fence, and the neighbor’s aren’t too
happy…