I'm sure it's been discussed here or something but, are there any downsides to simply flat out disabling a few cylinders on an engine other than maybe roughness or something? Like could I turn a V8 into a 4cyl by just putting metal shims or something to block the intake and exhaust, or possibly pulling the lifters out so the valves never activate, or both... Or even down to 2cyl, or taking a factory 4cyl down to 1cyl. For that matter what if a person removes entire con rods/pistons from an engine so there's no friction, maybe just replacing it with a slug of similar weight on the crank so it doesn't imbalance while spinning??
Why do normal 'variable displacement' systems have to deactivate the valve mechanically, why not just some kind of butterflies in the intake or something? (or/and the exhaust but I don't see how that would affect anything even left unblocked)
This is really open ended, i'm hoping someone whose researched/tried it more might be able to bring me up to speed. The use would not just be for automotive - going to 1/4 the cyl originally designed is so little displacement you'd rightfully ask why not just use a smaller engine - the answer is sometimes junkyard car engines are even cheaper than small engines in a given size, slowing down rpm only goes so far - 've been given engines if I wanted to take them, yet the only application I wanted to use them for - like a small generator of maybe 10hp sustained they would still be grossly oversized for running on all cylinders... such a strategy could actually combine with extended in place engine life postponing rebuild/replacement by switching which cylinder you were firing on too, putting the old piston/con rod back in for one of the other cylinders and moving the crank weight over to the one you wore out. Heck maybe it could be a way to still use engines otherwise damaged - like cracked or scored cylinder walls but you aren't using them all so just disable those so damaged.
That's a good example of engines often available for free.
I eventually want to experiment with temporary deactivation too like the new systems do but before I bother with that I figure better to get a handle on how to permanently do it so see if there are alternatives to just mechanical valve actuation.