Forum for competition engine enthusiasts. RIP Guy Croft 09/11/2020 - This forum will continue both as a source of information and as a memorial to Guy.
The cam pulley on the FIRE 16v is not located by a traditional keyway. To adjust the timing you simply fit the official Fiat cam locking tool, slacken the retaining bolt adjust the angle and then tighten again.
The same trick can be used at the other end of the head to adjust the chain gear that synchronise the two camshafts.
When adjusting this which was would you turn the pulley? I'm guessing it would be very slight movements?
What would the effects be on the inlet cam if the pulley on the exhaust is advanced?
Really what you are aiming for is accurately synchronising the camshafts with TDC on the crankshaft. As such there is very little need for altering the timing between the inlet and exhaust other than to do the same trick.
When you change the timing on the pulley you are changing both cams by exactly the same amount. The locking tool fixes the position of the camshafts (or rather one of them) so that you can alter the position of the pulley to obtain the optimum angle.
Normally it is only the pulley that you would rotate to change the timing.
In general the setup process would go something like this:
Before fitting the head to the engine set the inlet camshaft to match TDC and lock it in position.
Adjust the exhaust camshaft to match TDC and tighten the drive gear to lock the position relative to the inlet camshaft.
Set the block at TDC and fit the head
Provided the crank is locked at TDC and the camshafts at the same then it is just a matter of fitting the timing belt, setting the cambelt tension and tightening the pulley in position.
Unlock the crank and cams and rotate the engine through a few cycles and then check the timing is correct and the cambelt tension is within tolerance.