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Pistons:
Forged pistons recommended for all applications. Cast
and hypereutectic pistons can be used but should be limited
to lower horsepower (approx 450-500 hp) applications.
Compression ratio:
For pump gas (91-93 octane) applications, a compression
ratio of 8.5:1 to 9:1 is recommended for boost levels
of 8-10 psi. Higher octane fuel will allow you to run
higher boost levels, approximately 1 psi for every 2 points
of octane. To determine the maximum boost level for your
compression ratio (using pump gas), refer to the enclosed
compression ratio chart.
Heads:
The same rules for normally aspirated engines apply to
supercharged motors. Higher flowing heads will help generate
more horsepower than stock heads. Supercharging produces
a percentage gain in horsepower; by starting with more
base horsepower a modified motor will receive a larger
total hp gain (from the same percentage gain). Porting,
especially on the exhaust side is recommended. Aluminum
heads will allow you to run approximately 1 psi more boost
than cast iron heads due to their ability to dissipate
heat.
Cam:
Lobe separation: 112 to 116 degrees Split pattern:
Exhaust duration and lift approximately 10 degrees and
.010, respectively, greater than intake. Install cam straight
up. Contact a cam manufacturer for lifts and durations
that best suit your application.
Crankshaft and rods:
Cast up to 450 horsepower, forged for higher horsepower
or for rpm levels above 6,000 rpm.
Exhaust:
Headers are recommended. The size of headers are dependent
on whether you are wanting to create more low end torque
or high rpm horsepower.
Intake manifold:
Dual planes are recommended to improve low end torque,
however may require staggered jetting for good fuel distribution
with carbureted applications.
Carburetor:
Holley double pumper w/ mechanical secondaries.
600 cfm (#4776) for up to 500 hp
650 cfm (#4777) for up to 650 hp
700 cfm (#4778) for up to 750 hp
750 cfm (#4779) for up to 900 hp
All carburetors will require removal of the choke
assembly and choke horn, replacement of the floats with
the solid nitrophyl floats and jetted to suit your motor.
Fuel pump (carbureted applications):
Your fuel pump must be capable of supplying the proper
amount of fuel flow at the maximum operating pressure. To
determine maximum operating fuel pressure requirement,
add your maximum boost pressure to your initial idle fuel
pressure.
Example:
(8 psi idle fuel press.) + (10 psi boost press.) = 18
psi max. fuel press.
multiplying this figure by 1.2 (20% safety factor)
gives us 21.6 psi
To determine required fuel flow, multiply your total expected
horsepower by a bsfc (brake specific fuel consumption)
of .65. This will give your fuel flow requirement in 1bs/hr.
To convert to gallons per hour, divide this figure by
5.87.
Example:
(500 boosted hp) x (.65 lbs/hr/hp bsfc) = 325 lbs/hr fuel
flow
325 lbs/hr / 5.87 lbs/gal = 55.4 gals/hr fuel flow
Therefore, a fuel pump capable of providing a minimum
fuel flow of 55.4
gals/hr at a pressure of 21.6 psi is required.
This can be accomplished by an all electric high pressure-high
flow fuel pump (i.e. SX #18201, B.G. 400, Magna-Flow 250
or similar type fuel pump) and a return style, boost sensitive
fuel pressure regulator (Mallory #4309 or similar). Or
by using a boost referenced mechanical fuel pump only
(up to 500 hp) or a boost referenced mechanical fuel pump
in conjunction with a low pressure electric pump (i.e.
Holley blue, Comp 140 or similar).
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