Power Combinations

Performance Level

1

2

3

4

5

6

7

Performance Description

Torque and City Car

RV and Commuter

Mileage and Power

Street Performance

Hot Street Performance

Street / Strip

Competition

Applications

Good fuel economy, light to medium towing, improved low-end for city use

Good fuel economy, medium towing, improved mid-range performance for everyday use. No internal mods. are required.

Daily driver, Mild performance rebuilds, Some Towing

Good upper mid-range performance for street machines, Works well for medium and heavy towing

Edge of Daily Driver Street Cars, Occasional driver

Edge of Streetability, Mild bracket racing

All race engines

Horsepower / Cubic Inch

0.5 to 0.7

0.6 to 0.8

0.7 to 0.9

0.8 to 1.1

0.9 to 1.2

1.1 to 1.5

1.5 to 2.0

Cruise RPM

1,400 to 1,800

1,600 to 2,200

2,000 to 2,600

2,400 to 3,200

2,800 to 3,600

3,200 to 4,000

Not applicable

Power Band RPM

Idle to 3,600

1,000 to 4,000

1,400 to 4,400

1,800 to 4,800

2,200 to 5,200

2,600 to 5,600

3000+

Peak Horsepower RPM

4,600

5,000

5,400

5,800

6,200

6,600

7000+

Idle Speed

800 RPM or less

850 RPM or less

900 RPM or less

950 RPM or less

1,000 RPM or less

1,100 RPM or less

1,100 RPM or more

Idle Smoothness

stock smooth

smooth

slight lope

small lope

has a lope

has a lope

will be rough

Volumetric Efficiency

70 to 85%

75 to 90%

80 to 95%

85 to 100%

90 to 105%

100 to 115%

110 to 125%

Compression Ratio

9.5

8.5 to 10.0

9.0 to 10.5

9.5 to 11.0

10.0 to 11.5

10.5+

11.5+

Carburetor

Recalibrated Stock

Recalibrated Stock or Small 4-bbl (445 - 556 cfm)

Small 4-bbl (500 - 619 cfm)

Med. 4-bbl (557 - 682 cfm)

Med. 4-bbl (616 - 746 cfm)

Large 4-bbl (677 - 810 cfm)

Single or Multiple Carburetion (738+ cfm)

Intake Manifold

Stock dual plane

Stock or Low Rise Aftermarket Dual Plane

Low Rise Aftermarket Dual Plane

Low Rise Single Plane or Medium Rise Dual Plane

Low Rise Single Plane or Medium Rise Dual Plane

Medium Rise Single Plane

High Rise Single Plane or Tunnel Ram

Cylinder Head

Stock

Mild Cleanup of stock castings

Mildly ported stock (bowl work, gasket match)

Ported Stock (bowl enlargement, gasket match, larger valves) or Aftermarket w/ mild cleanup

Ported Stock (bowl enlargement, gasket match, larger valves) or Aftermarket Stage 2 porting

Aftermarket Stage 2 or 3 porting

Aftermarket Race or Aftermarket Stage 3 ported

Camshaft Type

Hydraulic

Hydraulic

Hydraulic

Hydraulic / Mechanical

Hydraulic / Mechanical

Hydraulic / Mechanical

Mechanical

Lift

0.370" to 0.410"

0.400" to 0.450"

0.440" to 0.480"

0.470" to 0.500"

0.490" to 0.520"

0.510" to 0.550"

0.550"+

Intake Dur. @ 0.050"

180° to 195°

190° to 205°

200° to 215°

210° to 225°

220° to 235°

230° to 245°

245°+

Exhaust Dur. @ 0.050"

190° to 205°

200° to 215°

210° to 225°

220° to 235°

230° to 245°

240° to 255°

255°+

Exhaust Manifold

Stock

Stock or Tri-Y Headers (1 1/2" max.)

Small diameter tube headers (1 1/2")

Small diameter tube headers (1 1/2" or 1 5/8")

Medium Diameter Tube (1 5/8" or 1 3/4")

(1 3/4")

Large Diameter Tube (1 3/4" min.)

Exhaust

Stock or dual (2" max.)

Low restriction dual (2" max.)

Low restriction dual (2 1/4" max.)

Low restriction dual (2 1/4" min.)

Low restriction dual (2.5" min.)

Low restriction dual (3" min.)

Open

Ignition

Stock distributor and electronic ignition

Recurved distributor and electronic ignition

Recurved distributor and electronic ignition

Recurved or performance distributor and electronic ignition

Recurved or performance distributor and electronic ignition

Performance distributor and electronic ignition

Performance distributor and electronic ignition

Transmission - Manual

3 or 4 speed

4 or 5 speed

4 or 5 speed

4 or 5 speed

4 or 5 speed

4 or 5 speed

4 or 5 speed

Automatic Stall Speed

stock (1,600 RPM)

stock (1,600 RPM)

2,000 RPM

2,400

2,800

3,200

3,500+

Rear End Ratio

2.75 to 3.25

3.00 to 3.50

3.25 to 3.75

3.50 to 4.00

3.50 to 4.25

3.75 to 4.25

4.00+