Owners manual

2 INSTALLATION INSTRUCTIONS
M S D • W W W . M S D P E R F O R M A N C E . C O M • ( 9 1 5 ) 8 5 7 - 5 2 0 0 • F A X ( 9 1 5 ) 8 5 7 - 3 3 4 4
PULLEY SIZE AND RATIO
The MSD DynaForce 120 and 160 Amp Alternators are supplied with a single groove V-belt pulley.
MSD offers a dual V-belt and a 6-rib serpentine separately. Also, if you require a special pulley, the
shaft of the alternator is a common 17mm shaft that will accept some other pulley systems.
The pulley supplied has a diameter of 2.80” and a 3:1 pulley ratio is recommended for the street. (As
an example, when your engine is at 1,500 rpm, the alternator should be at 4,500 rpm.) The DynaForce
Street Alternators can handle up to 18,000 rpm maximum. They are most efficient when operating at
about 2,400 alternator rpm and function best between 2,400 and 7,500 alternator rpm.
Figure 2 Alternator Dimensions.
2”
4.33”
5.98”
TO FRONT OF SHAFT
5.12” 6.61
Keep in mind that underdrive crankshaft
pulleys can affect the output of your MSD
alternator at idle and lower rpm ranges.
Therefore, underdrive pulleys are not
recommended for street use.
INSTALLATION
The DynaForce Alternators listed at the
top of these instructions are designed for
use in applications that require straight
mounts from top to bottom. Notice that the
two mounting tabs are 180° apart. This is
a common configuration for GM vehicles
used from the mid 1960’s through the mid
1980’s. Check to confirm that you have the
proper mount for your application before
disassembly (Figure 2).
Mount the DynaForce using the factory
hardware. Do not tighten the bolts entirely
at this time. Once mounted, it is important
to check the alignment of the pulleys. Place
a straight edge on the water pump or crank
pulley to the alternator pulley. If they are not
Crankshaft Pulley Diameter
Alternator Pulley Diameter
= Pulley Ratio
Pulley Ratio X Engine RPM = Alternator RPM
EXAMPLE:
EXAMPLE:
8.75"
2.8"
3.1 X 800 = 2480 Alternator RPM
= 3.125 Pulley Ratio
aligned, the alternator may require shimming. Also, note that some aftermarket brackets only have
one solid mounting point such as systems that incorporate a turnbuckle or heim joint for tension
adjustments. MSD recommends a secondary support to dampen vibration.
Note: If you are using anodized or powder coated brackets, it is recommended to connect a ground
wire from the alternator housing to the engine block.