What do Underdrive Pulleys do? Underdrive pulley systems increase engine horsepower by reducing the amount of power required to drive external engine accessories. For example, the alternator, power steering, water pump and air compressor rob horsepower from the engine. By replacing factory-sized crank and accessory drive pulleys with a resized pulley, the accessories are slowed, resulting in more horsepower available to the drive wheels. Typically, a set of Auto Specialties street pulleys will increase horsepower by 12-15, and increase mileage by 2 to 3 MPG. All pulleys are manufactured from Billet Steel or Aluminum, exceeding factory quality.

79-93
Underdrive Kit w/grooved WP
829125 ODG

79-93
Cobra WP

Year Engine Pulley Description Full Charge Info Image Nitride Hard Coat Black Alum Hard Coat Blue Alum Hard Coat Red Alum Hard Coat Clear Alum
05-07 4.6 L GT 25% HarmonicDampner
8% up 90
ASP527305
$245.00
01-04 4.6 GT 25% HarmonicDampner
26% Water Pump
8% Alternator
950 RPM ASP522328
$244.95
99-01 4.6 Cobra 25% HarmonicDampner
26% Water Pump
10% Alternator
950 RPM ASP522375
$244.95
96-00 4.6 GT 25% HarmonicDampner
26% Water Pump
8% Alternator
950 RPM ASP527328
$238.95
96-00 4.6 Cobra 25% HarmonicDampner
26% Water Pump
10% Alternator
950 RPM ASP527375
$238.95
96-00 4.6 GT 25% Alum Spacer
26% Water Pump
8% Alternator
950 RPM ASP527728
$136.50
96-97 4.6 Cobra 25% Alum Spacer
26% Water Pump
8% Alternator
950 RPM ASP527775
$136.50
94-95 5.0 26% Crank 750 RPM ASP523500
$65.00
ASP823500*
$65.00
94-95 5.0 26% Crank
30% Water Pump
2 3/4″ Alternator
950 RPM ASP525928
$125.00
ASP825928*
$139.00
79-93 5.0 25% Crank 850 RPM ASP520100
$67.00
ASP820100*
$68.00
85-86 5.0S/Tran 25% Crank
2 3/4″ Alternator
1100 RPM ASP520105
$112.00
ASP820105*
$89.95
79-93 5.0 25% Crank
15% Water Pump
850 RPM ASP520120
$125.00
ASP820120*
$106.00
79-93 5.0 25% Crank
15% Water Pump
1 7/8″ Alternator
700 RPM ASP520124
$135.00
79-93 5.0 25% Crank
15% Water Pump
2 1/2″ Alternator
950 RPM ASP520125
$135.00
ASP820125
$135.95
ASP829125
$135.95
ASP822125
$135.95
ASP824125
$135.95
79-93 5.0 25% Crank
15% Water Pump
2 3/4″ Alternator
1100 RPM ASP520128
$135.00
ASP820128
$135.95
ASP829128
$114.95
ASP822128
$114.95
ASP824128
$114.95
79-93 5.0 25% Crank
15% Water Pump
3 1/2″ Alternator
1500 RPM ASP820126*
$184.95
2001 4.6 GT 26% Water Pump Pulley
Short water pump
950 RPM ASP520123
$85.00
79-93 5.0 Cobra WP Pulley ASP520141
$75.00

Mustang V6

Above images in order from left to right; 1999-00 3.8L V6 stock dampner / new stock dampner with factory pulley removed / new 25% reduction crank pulley and new harmonic dampner
All ASP 25% Underdrive Street System Harmonic Dampner Design add 10+ Rear wheel HP.
Part# ASP820117 & ASP820122 *

1994-98 3.8 L Ford Mustang Crank Pulley

25% Reduction Crank and Alternator Pulley Kit,
This pulley kit will give you 9+ Rear wheel HP.
Part# ASP826308

Year Engine Pulley Description Full Charge Info Image Nitride Zinc Hard Coat Black Alum
2011 3.7L 25% dampner 850RPM ASP520144**
Call
05-10 4.0L 25% dampner 850 RPM ASP526400
$285.00
01-04 3.8/3.9 25% Dampner Crank Pulley 950 RPM ASP820122
$318.00
99-00 3.8 25% Dampner Crank Pulley 950 RPM ASP820117
$318.00
94-98 3.8 25% Crank 950 RPM ASP826300
$115.00
94-98 3.8 25% Crank2 3/4″ Alternator 950 RPM ASP826308
$120.00

* Clear HC., Red and Blue also available.
** Will not work on LS Lincoln

1989-94 Thunderbird Super Coupe 3.8L V6L

1989-94 3.8L S/C Blower Pulley
10% Blower Overdrive Pulley Adds 3 PSI Boost,
Adds 12+ HP Part# ASP52009

1989-94 3.8L S/C Street Pulley Kit
Street Pulley Kit 25% Reduction Crank Pulley,
29% Water Pump, 3″ Alt.Part# ASP520425
DISCONTINUED

Year Engine Pulley Description Full Charge Info Image Nitride Hard Coat Black Alum
94-97 4.6 25% Harmonic Dampner 26% Water Pump 15% Alternator 900 RPM ASP527328
$238.95
94-97 4.6 25% Crank 26% Water Pump 15% Alternator 900 RPM ASP527728
$136.50
89-95 3.8 SC 10% Blower Overdrive Adds 3 PSI Boost 950 RPM ASP520009
$109.95
90-98 3.8 25% Crank 2 3/4″ Alternator 950 RPM ASP826308
$120.00
90-93 5.0 25% Crank 29% Water Pump 2 3/4″ Alternator 950 RPM ASP523528
$125.00

Crown Victoria / Grand Marquis

Year Engine Pulley Description Full Charge Info Image Steel
81-89 5.0, 351W 25% Crank 850 RPM ASP928900
$150.00

Contour / Cougar with SVT Duratec

Year Engine Pulley Description Full Charge Info Image Clear HardCoat Alum
95-99 2.0L 15% Reduction 800 RPM ASP840110
$124.95

Ford Truck

Year Engine Pulley Description Full Charge Info Image Nitride Zinc Hard Coat Black Alum
02-09 4.6, 5.4 25% Harmonic Dampner26% Water Pump 850 RPM ASP527374
$227.95
97-01 4.6, 5.4 25% Harmonic Dampner26% Water Pump 850 RPM ASP528774
$227.95
01-07 4.2 Harmonic Dampner25% Crank Pulley 850 RPM ASP820130
$318.00
99-00 4.2 Harmonic Dampner25% Crank Pulley 850 RPM ASP820129
$318.00
97-98 4.2 25% Crank Pulley 850 RPM ASP826300
$115.00
92-08 3.0L Ranger 20% Crank Pulley 850 RPM ASP821120
$112.00
90-03 4.0L Ranger/Explorer 25% Dampner 900 RPM ASP526400
$285.00
80-86 5.0, 5.8 30% Crank 800 RPM ASP523000
$130.00
80-86 5.0, 5.8 30% Crank3″ Alternator 1000 RPM ASP523003
$150.00
87-97 5.0, 5.8 30% Crank 850 RPM ASP820100
$68.00
87-97 5.0, 5.8 30% Crank15% Water Pump 1100 RPM ASP520120
$125.00
93-94 2.3 25% Crank 1000 RPM ASP926500
$175.00

1999-2004 SVT Lightning Truck

1999-2004 5.4L Blower Pulley
1999-04, – 5.4 L Ligntning Truck Blower Pulley, 2.80″, adds 3 psi to engine and 23.2 extra hp,
Part# ASP520003 *

Year Engine Pulley Description Info Image Nitride Hard Coat Black Alum
99-04 5.4 Blower Compressor Overdrive Pulley 2.93″ Diameter(+2 to 3″psi) ASP520002
$109.95
99-04 5.4 Blower Compressor Overdrive Pulley 2.80″ Diameter(+3 to 4″psi) ASP520003
$109.95
99-00 5.4 Blower Crank Pulley 8.40″ Diameter (+4″psi) ASP820116ps
$225.00
01-04 5.4 Blower Crank Pulley 8.40″ Diameter (+4″psi lightning +2″psi harley) ASP820116aps
$225.00
99-00 5.4 Blower Crank Pulley 9.00″ Diameter (+6″psi) ASP820116ps9
$225.00
01-04 5.4 Blower Crank Pulley 9.00″ Diameter (+6″psi lightning +4″psi harley) ASP820116aps9
$225.00

Early Model Crank Pulleys

Year Engine Pulley Description Info Image Steel
65-69 289 (3 Bolt) 25% Reduction – 1 V-Groove ASP922900
$125.00
65-69 289 (3 Bolt) 2 V Grooves ASP924200
$150.00
70-78 302, 351 W 25% Reduction – 1 V Grooves ASP924000
$125.00
70-78 302, 351 W 2 V Grooves ASP924100
$150.00
68-87 429, 460 25% Reduction – 3 V Grooves ASP925600
$150.00

Alternator Pulleys

For Serpentine Belt Systems 
32% overdrive alternator pulley.
Increased charging capacity.
CNC -machined billet steel nitride coated.

Year Engine Pulley Description Info Image Nitride Zinc Hard Coat Black Alum
Early Model 3 1/4″ 1 V-Groove ASP820003
$54.95
79-95 5.0 1 7/8″ Alternator ASP520004
$32.00
79-93 5.0 2 1/2″ Alternator ASP520005
$38.00
ASP820005
$34.00
79-95 5.0 2 3/4″ Alternator ASP520080
$26.95
ASP820080
$34.00
79-93 5.0 3 1/2″ Alternator ASP820006
$95.00