RJC Racing Billet Aluminum Pulleys

Performance is a funny thing. When the discussion turns to improving a vehicles acceleration capabilities, the first thing to come to mind is adding horsepower.. This makes sense, since acceleration is merely a function of horsepower vs. weight: the more power you have to accelerate a given weight, the better it will accelerate. Though adding horsepower is a surefire method of making your car faster, the flip side of the equation is also true. Removing weight from your car has the same effect as adding horsepower; after all, the engine now has much less mass to get moving.

Any rotating object offers resistance to a change in its rotational speed. It takes power to start spinning and power to stop it. Once its spinning, the resistance drops off, as it is much easier to keep it spinning than to start or stop it. The resistance is known as moment of inertia (MOI). The MOI of an object is determined by the diameter and the mass of the object. Increasing either the outside diameter or the weight of the object will increase the moment of inertia. The larger the moment of inertia, the more power it takes to start or stop the object.

The formula for moment of inertia is MOI = 1/2 x Mass x Radius2 As is evident from the formula, increasing the diameter has a much greater effect on the MOI than increasing the weight. Doubling a components weight will only double the MOI value, while doubling the diameter will quadruple the MOI value.


By going to RJC Billet Aluminum Pulleys you can loose over 9 Lbs. of reciprocating weight. This is equivalent to removing 95 lbs. of non reciprocating weight.

Pulley Weights (All of our pulleys are 100% stock dia.)

Factory Stock Crank Pulley with intercooler fan 8+lbs.
Factory Stock Crank Pulley no intercooler fan 6lbs. 2oz.
RJC Billet Aluminum Stock Style Crank Pulley no fan 1lb. 10oz.
RJC Billet Aluminum Race Style Crank Pulley Razor 1lb. 1oz.
RJC Billet Aluminum Race Style Crank Pulley Undersize 15oz.

Factory Stock Steel Water Pump Pulley 1lb. 8oz.
Competitors Billet Aluminum Water Pump Pulley 8oz.
RJC Billet Aluminum Water Pump Pulley “Razor Style” 7oz.

Factory Stock Steel Power Steering Pump Pulley 1lb.
RJC Billet Aluminum Power Steering Pulley “Razor Style” 7oz.

Factory Stock Steel Idler Pulley 10oz.
RJC Billet Aluminum Pulley “Razor Style” with bearing 4oz.

Factory Stock Steel alternator Pully 7oz.
Competitors Billet Aluminum Alternator Pulley 3oz.
RJC Billet Aluminum Alternator Pulley “Razor Style” 2.3oz.

The razor and stock style pulleys are available in polished aluminum and anodized black
for that “Stealth” look.


WeightThese pictures show the weight of the aluminum race pulley. It weighs aprox. 1 lb 3 oz. This is 5 lbs lighter than the stock pulley without the intercooler fan and about 8 lb lighter than the stock pulley with the fan. That is quite a reduction in reciprocating weight. The two pictures on the bottom show the stock pulley with the weight of a stock pulley (right) without the intercooler fan. The intercooler fan weighs aprox 3lb more than this. (weight shows 6 lbs 2 oz.)

Return Policy

This warranty does not cover any failure due to abuse, accident, or neglect. The liability of the manufacturer shall not exceed the original purchase price of the unit. Read More..

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