Revised Ford Pulley Specs?

[Mark Madison]

Originally Posted by Jesse Kershaw

The truth is actually much simpler than the conspiracy theory.

The common TVS listed pulley sizes of 76mm (2008/2012 CJ) and 72mm (2010 CJ) are determined by us using a caliper with a 2.5mm gage ball.

The gage ball fits in the groove and helps determine the theoretical centerline of the belt. Our engineers use this diameter to determine the belt length of the accessory drive system. Thus the 76mm, as we advertise it, is actually the centerline of the belt on the pulley.

Because of this measuring method if you measure the pulley with traditional calipers to the top of the groove the number would be less than 76mm or 72mm respectively.

The pulley's as delivered on the Cobra Jet's and the samples provided to NHRA at the time of production are identical and have never been altered.

For the 5.4L w/2.3L TVS supercharger the following SC pulley sizes are as delivered.
2008 – 76mm w/gage ball – actual minimum diameter = 73.95mm (2.911”)
2010 – 72mm w/gage ball – actual minimum diameter = 69.95mm (2.754”)
2012 – 76mm w/gage ball – actual minimum diameter = 73.95mm (2.911”)

Whipple does not measure like the OE. Their 4” pulley (2010/2012 5.4L engine with 4.0L Whipple SC) is 4” to the top of the rib +/- .010” making the minimum diameter 3.990”

The Whipple 3.5” pulley (2013 5.0L engine with 2.9L Whipple SC) is 3.5” to the top of the rib +/- .010” making the minimum diameter 3.490"

Super Stock racer TIm Kish is intimately familiar with this as he works in the Eaton supercharger division.

Whew, for a moment I thought we had another double secret camshaft debacle on our hands. Mark Madison