Finding just a bit more horsepower
By Larry Wallace, Circle Track Magazine
August 30, 2001
7:02 PM EDT (2302 GMT)
Finding horsepower depends
mainly on what type of racing
you are doing, what the rules
are and what components the
series allows you to run. Then, you
spend your time maxing out those
rules.
First, you want to start with the
carburetor and work your way down.
Some racing series only allow you
to run a two-barrel or other small carburetor.
What type of carburetor
you run will determine what you
do from there down to find
that extra bit of horsepower.
If
you have to use a smaller carburetor,
the next component
you want to look at to gain some
horsepower will be the camshaft. The
camshaft should be tailored to whatever
carburetor you run. Your best bet
would be to go with a camshaft
from a company like Comp
Cams or Crane.
Let them
recommend what type of
camshaft you should run. What
you want to do is gather all the information
you can on the rules, as far as what restrictions there are on cubic-inch
carburetors, whether or not you
have to run cast-iron heads and
whether you have to run a flat-tappet
cam.
Once you get that information,
give it to your cam manufacturer and it
should recommend the best possible
camshaft for your particular application
and series.
The next biggest thing as far as
finding some extra horsepower is the
cylinder heads.
First, you need to find
out whether or not your racing series
allows you to run an aluminum
aftermarket head or if you have to run a
cast-iron head.
If it is a cast-iron head,
you need to find out if it can be an
aftermarket head or if it has to be factory
supplied. If you are knowledgeable
about cylinder heads, you can do some
work on them yourself.
If not, I recommend
going to a reputable machine
shop to have this type of work done.
Another thing you can do is look
around to see who is running good and
take your cylinder heads to the same
place they are getting theirs worked on.
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Ryan Newman's Penske-powered ARCA engine has visited Victory Lane twice this year.
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As far as what can be done to the
cylinder heads to gain some
horsepower, there again, it depends on
the rules. Unless you are into some
high-end racing, there are very few
series across the country that will allow
you to do a lot of cylinder head work.
Basically, a valve job and a clean-up of
the intake and exhaust pockets are
about all you can do to them.
However,
there is a lot of power that can be
gained or lost if you decide to work on
your heads yourself and you don’t
know what to do, so it is still better to
farm that out to whoever is doing the
local stuff and is fairly competitive.
If you have to run a flat-top piston,
no pop-ups, such as in some of the
ARCA racing divisions, cut the deck on
the block to get the minimum
clearance.
You want to cut it down to
minimum clearance between the piston
and the head to try to gain all the compression
you can.
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The type of carburetor you run will determine where you can find extra horsepower.
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In the ARCA Sportsman division
they have a cubic-inch-to-weight rule.
If you are running on a short, really tight
racetrack where it is hard to hook up,
you are probably better off running the
smaller engine—less than 360ci—and
take the 200-pound weight break.
If it
is a larger track and you are able to
hook up, it is probably best to find the
biggest engine you can for whatever
make and model you are running rather
than avail yourself of the weight break.
It is hard to put a number on how
much horsepower can be gained by
doing headwork. If you start with after-market
cast-iron heads, like Dart, you
are basically getting a right-out-of-the-box
product that doesn’t need a lot of
work.
If your particular sanctioning
body requires you to use factory origi-nal
cylinder heads, there is quite a bit
of power to be gained.
You can gain
probably 20 to 30hp by going in and
really working the head over. However,
if you are allowed to run aftermarket
heads like Dart, I believe you will be
better off.
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A camshaft.
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With the bottom end of the engine,
there again, you have to go with whatever
the rules allow. What compression
are you allowed to run? Once you find
that out, go to the maximum amount.
Finding a good local machine shop is
probably the best thing you can do if
you plan on building your own engine.
However, finding a good machine shop
that does good work can be pretty
hard. I’m not talking about a standard
rebuild shop, but a guy who does
some racing stuff and can guide you
along as you are building your engine.
You may pay a little more at a shop like this, but you will definitely be
ahead in the long run. Building
an engine with all-new
pieces will cost more going
in, but if you are going to run
over an entire season it is
better to start with as many
new pieces as you can.
You
might get by with used components,
such as the block
and maybe a crankshaft, but
most of the internal pieces of
the engine—valvesprings,
cam lifters, connecting
rods—it is wise to go with
new stuff and keep track of
the mileage. It costs more
going in, but over a season
of racing, it will cost less.
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Valvesprings
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BASIC MAINTENANCE can help you
with your horsepower gain
as well. If you properly maintain
your engine, you will not
lose any horsepower.
Start with mostly
new parts at the beginning of the year.
You especially want to have new
valvesprings. Before you actually run
the engine for the first time, use a
spring checker that works with the
engine assembled.
All you have to do
is pull the valve covers, check the
springs on the engine and write down
that tension. Periodically, after each
race, you need to check the
valvesprings.
When the valvesprings
start to lose between six and seven
percent in tension, you need to change
them. After some time running a particular
rpm you should get the feel as to
when the springs go. Change them out
regularly.
It may seem a little more
costly at first, but, one broken spring
and valve and you will have a torn up
engine, which will result in a repair job
that will pay for all your valvesprings for
a whole year.
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An On Head Valve Pressure Tester can check the spring pressure.
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OIL COOLERS Running an oil cooler is
another good bet. Keep a monitor on
the oil temperature while you’re
running. If you have an oil cooler
plugged in, it is really easy to plug in a
filter on the scavenge side that you can
take apart easily and check for any
excessive metal or wear.
If you see
something you know has an internal
problem, you can check it before
you totally ruin the engine.
The oil weight may
also affect
horsepower gains. Normally, on an
engine such as an ARCA Super Stock
or Sportsman type, you can get away
with running a light oil.
Penske Engines
runs a light oil in our Winston Cup cars.
We use Mobil synthetic. Oil has made
such tremendous gains lately. The only
thing you need to worry about with
these flat-tappet cams, like most of
these engines are required to run, the
oil needs to have more zinc than is normally
found in a production oil.
Zinc
helps with wear on flat-tappet cams. All
the oil manufacturers have been
required to take the zinc out because it
damages catalytic converters on street
cars.
More production cars are going to
roller-type camshafts instead of flat-tappets,
therefore not having zinc in the
oil does not harm the engine as it
would in a race car.
You can use an
additive to get the zinc back. A multiple
viscosity oil is OK, like a 20W-40 or
10W-30. Remember, the viscosity
needs to be matched with whatever
bearing clearances you are running.
A thin oil will not work with an excessive
bearing clearance, like 3,000 or more. If
you build the engine with bearing clearances
down around the 2,000 range,
you can run the light oil and there
should be a little power with that. CT
For more stories from Circle Track Magazine, visit the Circle Track Web site at www.CircleTrack.com
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