Oversized Pulley, Custom

Pulley, Idler, and belt

Rand Machine Works, a local machine shop here in Fresno, California, told me that it would be cheapest to have a ring built that is 170mm overall with about a 140mm center pressed over our stock pulley after it has been machined down for a flat fit.
Here is an old report of my custom pulley with some good pictures.

Front of the pulleyAn Arial viewBack of the pulley
For merely $213, a ring, made of tool-steel, was pressed over the stock pulley. The three set screws are 120 degrees of each other. I did not get this pulley re-balanced.

Very Small Idler Pulley

So just where did I end up finding an idler pulley as small as this one? Don't look now, but you already own one!

Ah! The 
Timing Belt Idler Pulley!

If you guessed Timing Belt Idler Pulley then you are correct!
Just order a timing belt idler pulley, flip it backwards, make a spacer, and wa-la! What a concept!

Notice the belt rap. And the idler is lose too!

Notice just how much the belt is going to be rapped around the clutch pulley once the idler pulley is tightened!

Engine is not ready *notice no timing belt, crank pulley is not bolted up*

With the idler pulley tightened, it is almost 1 1/4 inches higher than pictured. This causes the belt to rap up underneath the Supercharger clutch pulley.
This definately lessens the odds for belt slippage.


With this pulley setup on my SC12, it is pushing 12 psi boost @ 70 degrees F, and 13.5 psi @ 110 degrees F.
Not bad considering my valves are pushed lower and opened longer with my racing cams!

b a c k