Basic Engine Building Specifications

The following specifications are general guidelines offered to aide in building an engine for street use. For more detailed specifications regarding your specific application or for “strip only” use, please consult a professional engine builder.

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 carburetor’s 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 pressure) + (10 psi boost pressure) = 18 psi max fuel pressure

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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