Gona need help with what part is what inside the head. Rockers, pads, lobes, enclosed gears, roller bearings, lifters wells etc. I havnt a clue. I need a closer look at the 16 little things I removed before takin out the head.
Those 16 little things are the rockers, that actuate the valves, attached by spring clip to the hydraulic lifters (the tubular things).
The rockers have a central roller bearing that bears on the lobe of the camshaft that controls its opening and closing. At the opposite end of the rocker is a small pad that bears on the end of the valve stem.
The hydraulic lifter is an adjuster in this design, that sets the correct height of the fulcrum for the rocker. There has to be just the right amount of valve clearance (free play aka valve lash) to allow valves to seat fully in the head, when closed. No gap and the valve may be held slightly open, losing compression and possibly damaging the valves and head; also the rockers will press continuously on the cam causing wear. Too much gap and valves can't open fully because of lost movement so not enough air gets in and not enough exhaust gets out (and you get terrible rattles as the oscillating bits of metal hammer each other). In other engine designs a screw and locknut mechanism may be used to manually adjust free play, or shims are used. The lifters are devices to manage the correct clearance automatically, by the magic of hydraulics.
Each lifter contains a spring operated valve. In the head each sits in a well of oil that is pressurised when the engine is running - you'll see a small oil hole at the bottom of the 'well' through which oil enters under oil pump pressure, and a small hole in the side of the lifter body through which oil pumps up the adjuster just enough to raise that end of the rocker to the correct height for the rocker to be correctly operated by the cam lobe bearing down on its roller bearing.
Have a look at the lobe and you can see from the shape how it works. As the cam rotates, the lobe bears down on the roller bearing and the because the rocker is supported at the lifter end it 'rocks', opening and closing the valve.
(Whilst looking at the lobes of the cam, check that they all look smooth and unworn, without blueing or chips or deep scuffs or scratches. Cams are sensitive to neglected oil quality and can wear badly once the surface hardening is damaged. Also check the roller bearings of rockers for smoothness and absence of slop or signs of break-up, the rockers themselves for cracks or signs of bending, and the pad on the end of each rocker that bears on the valve stem tip, for damage and wear. It will very likely all be fine but if any of this stuff is knackered, now is the time to change it).
For correct operation and the right valve clearance, the internal parts of the lifter have to be free to move so they can 'pump up' correctly. They're small, with tight tolerances, and the oil supply hole is small, and over time they can accumulate sludge and crap that tends to prevent them working properly (= 'sticky lifters').
Most of mine are rather sticky and stiff. If I squeeze one end against the other, they barely move. Ned's advice of gently using a vice is designed to dislodge the sludge that is clogging them up and free up the mechanism. They only have a couple of mm of movement against internal spring pressure, when operating correctly, so don't strong arm them expecting more, they'll just break. Once you have a bit of free movement you can dunk them in brake cleaner and pump them to inhale the solvent and expel the crud. Once they're free, squeeze them to expel brake cleaner and leave them to dry out. Then exercise them in some clean engine oil to try and fill them somewhat. They will fill up to the correct extent once you start the engine, but may well make a scary rattle for a brief while until the engine has pumped them up.
On some designs of hydraulic lifter, you can dismantle them to clean them out more thoroughly. I don't know about these Fiat ones, but I'd avoid it if possible. There's usually a collection of tiny parts including springs, shims, balls, sleeves and pingfukkits that are easily lost and/or don't want to go back together easily.
All the bits inside the cambox need to be free of grit and well coated in fresh new oil as you reassemble.
PS: You only need the camlock in the front hole, for the exhaust cam, when installing the timing belt. If you use the rear, inlet cam lock, it will just get in the way of replacing the inlet and HP fuel pump, and it isn't needed because the two cams cannot move independently of each other. You get both with a timing kit because both are needed if you have removed one or both cams from the cambox. They are both required to time the cams to each other.