How to identify original equipment Fiat-Lancia cam pulleys

Crank, rods, sealing, pistons, block, flywheel etc
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Guy Croft
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How to identify original equipment Fiat-Lancia cam pulleys

Post by Guy Croft » Fri Jun 23, 2006 3:15 pm

How to ID Fiat Twin-Cam pulleys

There is one infallible way to determine which-is-which, irrespective of whether the camwheels have flanges or not.

Draw 2 circles on a piece of paper to represent the camwheels. In the centre of each draw the 12.5mm bolt hole, and then a straight line from the centre of the hole to outer dia of the camwheel. A short distance from the centre and on this line, draw the dowel hole on each camwheel.

Towards the outer radius of the camwheel there will be a timing hole or a notch, sometimes annotated with a degree code number (can often only be made sense of with Fiat microfilm parts data), sometimes not. Likewise the early camwheels were marked A (achiuso I think), intake, and S (scarifico), exhaust. You won't always find A and S and unless you are swapping camwheels around and degreeing them in to optimise the performance ignore all other markings except the actual timing hole or notch.

On one camwheel, draw a timing hole near the outer radius to the left of the line you've just drawn, and on the other draw the mark to the right of the line.

If you now compare your drawing with the camwheels you will see that they correspond to what you have drawn. The inlet camwheel has the timing mark to the left of the (imaginary) line thru the dowel hole and wheel centre. The exhaust camwheel has the timing mark to the right of the line.

The camwheels rotate clockwise viewed from the crank nose. An easy way to remember is that the inlet timing mark is before the line - the cam being before full lift at tdc, and the exhaust has it after the line - the cam being, as it were, after full lift.

With the exception of the turbo and Volumex units the inlet and exhaust cams on the TCs are identical pairs. The dowel holes in the cams are always in the 6 o'clock position directly opposite no 1 cam lobe, since the cam grinder uses the dowel hole as the angular datum. Differences in cam settings a re achieved by different camwheels alone.

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