The XK8 bonnet is surprisingly heavy and its weight is balanced differently on the hinges, so it falls down as you state, but the way the XJ bonnet is hinged, down low at the front means the weight bears more or less down vertically, so not much weight at the rear to engage the pins, which also seem to need quite a bit of force to overcome. To use struts on the XJ, you would probably need to disable the front bonnet springs, otherwise you are just adding to the resistance.
I thought the struts actually add more force right at the closing time, when the pins touch the latches, therefore removing the need to build that force from kinetic energy by swinging the bonnet down at speed…
But, I agree that the springs would probably be redundant.
i have an XJ6 S2, i thought of the same thing about the struts, the problem i found was where to mount them without binding/jamming on body work engine bay, even looked at fitting vertically in the forward space of radiator, would get interfered by H/light units etc also struts most likely be in the way of working on the car, what i did is investigate the front springs settings and adjusted the bottom block shafts that the springs attach to as well as reduce the tension slightly, i also removed the hood lock at the front and created a new sliding hood lock which allows me to open the hood closer to vertical, now when i close the hood it’s just a gently push and the weight does the rest…
you’re right, of course - the method of closing a SII hood is rather agricultural: let it come down at full speed and lock! That being said - everyone watching so far was surprised that the expected “slam” - something like the impact of the Chicxulub asteroid - came out surprisingly clean and smooth. Actually, the hood is braked down (springs or air compression?) and the spring loaded pins engage. But, sure enough, I don’t hear a “wiiiiing” after the soft “schlup”
Exactly, Elinor! The surprise really is that the clever spring design slows down the fall of the hood to exactly the right speed and momentum necessary to engage the pins under spring load. No struts required. Nothing else.
Today, every car is equipped with power steering or power windows. Some cars need them, some customers want them. But in many cases it is simply cheaper to throw in assistance than to thoroughly design mechanical devices.