ARCO Pulleys

Pulley Type
OD (mm)
Bore (mm)
Grooves
Hub to Groove Center(s) (mm)
Notes




6G K Pulley
49
17
6-rib
—
Standard pulley


DV V-Belt Pulley
81
17
2 (3/8" or 1/2")
13.5 (1st), 30.5 (2nd)
Larger diameter dual-groove V-belt


DV V-Belt Pulley
71
17
2 (3/8" or 1/2")
22 (1st), 41 (2nd)
More offset dual-groove V-belt


6G K Pulley
60
17
6-rib
5.6 (1st groove)
Slightly larger than standard


6G K Pulley
64
17
6-rib
8.6 (1st groove)
Mid-size 6-rib


8G K Pulley
65
17
8-rib
8 (1st groove)
Higher output applications


10G J Pulley
53
17
10-rib (J)
—
Compact, high-rib density




The outer diameter (OD) of a pulley directly affects the rotational speed (RPM) of the alternator or accessory it drives. Here's how it works:
Basic Relationship:

Larger OD pulley → slower alternator RPM
Smaller OD pulley → faster alternator RPM

This is because the pulley acts as a gear: the engine crankshaft turns the belt, and the belt turns the alternator pulley. The ratio between the crankshaft pulley and the alternator pulley determines how fast the alternator spins.
Example:
If your engine crank pulley is 150 mm and your alternator pulley is:

50 mm → alternator spins 3× faster than the crank
75 mm → alternator spins 2× faster

⚠️ Why It Matters:

Too small a pulley: Alternator may overspeed at high engine RPMs, risking damage.
Too large a pulley: Alternator may undercharge at idle or low RPMs.


Here’s how different alternator pulley outer diameters (ODs) affect alternator RPM, assuming a crankshaft pulley OD of 150 mm and engine speed of 3000 RPM:



Alternator Pulley OD (mm)
Alternator RPM




49
9184


60
7500


64
7031


65
6923


71
6338


81
5556







Pulley Type
Belt Type
Groove Shape
Common Use




DV
Dual V-belts
Deep V
Marine, industrial, legacy systems


K
Serpentine (3.56 mm rib spacing)
Multi-rib
Automotive, marine, high-load


J
Serpentine (2.34 mm rib spacing)
Narrow multi-rib