I changed the belt on my boy's 2012 VVT 1.4 8valve Punto - in essence the same setup? I wanted to find out if you could do it without slackening that VVT pulley bolt. (I'm a great believer in letting sleeping dogs lie!) - And, by gum, that torx bolt is super tight isn't it!
I wanted to be absolutely sure I'd got it right so I bought the timing tools (I had our own 1.2 8valve - non VVT - 2010 Panda to do as well). I used the crankshaft tool to set the engine up at it's locking point and checked that the cam locking tool was lining up but did not slacken the cam pulley torx bolt. (you can be one crankshaft rev out - 180 degrees on the cam - which you need to check by looking at the end of the cam - bell housing end of engine) I then Tippex marked the cam pulley, cylinder head and cambelt and, down below, the crank pulley, block face (oil pump housing actually) and cam belt. Loosened the tensioner and removed cam belt, tensioner and water pump. I always do a water pump where it's part of the belt drivetrain. After installing the new water pump I transferred the tippex marks from the old belt to the new one and fitted it onto the pulleys so that the crank and cam pulley marks, marks on the new belt and marks on the head and oil pump casing all lined up. After tightening the spring loaded tensioner and rotating the engine a few times by hand "just to be sure" I rechecked the timing using the timing tools on the crankshaft and camshaft. Everything lined up exactly. So no slackening of that cam pulley bolt was needed. Don't expect the tippexed marks to line up again after rotating the engine though. (they probably would if you turn it over many times but not after just a few).
I wondered if it was a fluke so repeated the procedure on the Panda and the result was the same! again no need to slacken that pulley bolt.
I checked with great care when I was using the timing tools and everything was absolutely spot perfect lined up! So, as long as no-one else has been in there before you, slackened "that bolt" and failed to set it up properly before retightening "that bolt" I believe there is no need to slacken it. Both our engines were getting their first belt change so had not been touched before and were as set up at the factory. The big plus for me here is that now I know this "tippex" method works and that the cam pulley is tightened to the correct position on the camshaft, I will not need to remove the cam cover next time. I'll simply mark it all up with the tippex and swop the belts. I would not be happy to do it this way on an "unknown" engine as I would be too worried someone might have tightened the cam pulley up in the wrong position.
Lastly, Although I felt confident about actually doing the belts and water pumps etc, having done many in my life, I got my knickers in a bit of a twist leading up to doing these cam belts because I had read, here on the forum and in other online posts, that when a new belt is fitted the ECU requires a reset to be done - Fiat call it a "Phonic Wheel Relearn" (the Gates - Gates being my favourite brand - instructions actually mentions it and my local Fiat main agent say they do it as a matter of course as part of the procedure). Apparently the problem is to do with the way the ECU perceives the signals from the camshaft sensor and crankshaft sensor to be relating to one another. The argument is that fitting the new belt disturbs - albeit only very slightly - this relationship. I wondered if, by not slackening "that bolt" the relationship would remain undisturbed (given the very tight tolerances to which synchronous belts are manufactured). I'm pleased to say that some 6 months on, neither vehicle has required this procedure. For your info, having read extensively about it and talked to local Fiat indy garages, if it's going to do it it normally brings the engine warning light on when cruising at speed out on country roads - it would seem that it often won't light it if the car is only poodling around. When a scanner is applied fault codes come up for a missfire, which leads people off on a wild and expensive witch hunt looking at plugs, ignition leads, coils and even the ECU itself. The big give away is that as the driver you will not have felt any evidence of missfiring - because, of course, it's not! it's just the ECU trying to make sense of the missmatch on the sensor signal syncronization.
Facing this possibility I decided to buy my own fully registered copy of
Multiecuscan (from Gendan - good people)
https://www.gendan.co.uk/product_FESPKG.html which would let me carry out the full procedure. As it turned out I didn't need it for this but I haven't regretted it for one minute. It's a great tool. Lets you do service resets, read fault codes, activate components for testing, read and graph sensor outputs and lots more - Almost everything the dealer can do with his tool! I start every service by scanning the whole vehicle for codes which gives you a jolly good idea of any problems there may be in addition to the simpler service tasks I'm about to undertake. Have a look at their website (if you haven't already)
https://www.multiecuscan.net/ A lot of the folks on here use it and there's lots in the forum about what you can do with it. There's a free version on the
Multiecuscan website which you can download and run in simulation mode which will give you a very good idea of what it can do.
So. Good luck with it all. Hope this was helpful.
Kind regards
Jock