Still consider my compression and vacuum testers my most important troubleshooting tools. It drops an inch every thousand feet above sea level at 1,100 feet so expect to read 19"/Hg. Little off topic but use a water column tester for furnace checking, gas valve is typically at 3.5"/H2O.
Mention one friend laid out 1,500 buck with a misfire from a shop, installing new overpriced stuff, stuck on my vacuum gauge and found loose intake manifold bolts. Happen with aluminum engines if the cold roll steel bolts don't corrode first.
One nice thing about VVT got rid of that stupid EGR valve sitting on top of a hot manifold, one little leak, no EGR, unleaded burns at 2600*F burn holes in your pistons and eats up your exhaust valve. And if that EGR stuck open, won't start.
Cars were so simple back then, 6V on the coil to points to ground was the ignition system, single barrel carb easy to clean, and even some Fords had a gravity fed carb with no way overpriced POS fuel pump in the tank to go bad.
But ignition, fuel, compression and vacuum is still the same.
Had luck with sticking hydraulic valve lifters by adding seafoam to the engine oil, can says about one ounce per can, may add two, drive it for a day, then change the oil. Practically all new vehicles are using VVT, gives far better performance over a wide rpm range.
In a vehicle like my 70 Buick with a fixed cam, peak torque curve was set at 2,700 rpm, that translated to the best fuel economy at 70 mph, would average 20 mpg until AH Nixon dropped the limit, strictly enforced to 55, then only 16 mpg, truckers were screaming, not only poorer economy, made less as were paid by mileage, not time. And only about 50 years to get 70 mph back.
Actually with VVT, get better fuel economy driving slower because wind resistance increases by the square of speed. And the torque curve is much flatter. Varnish in engines building up over time is common with conventional oils, synthetics don't have this problem. Only cost me two bucks more to change my oil DIY, but crooked dealers charge 40 bucks more.
Did purchase an old but hardly used boat from an old couple with a Volvo outdrive on it. Used conventional oil in the lower end. Wouldn't shift properly, electric, took it all apart and cleaned the varnish off all the parts and used synthetic, no problems after this. Synthelics cured the varnish build up problems.
In this thing, if the engine calls for a camshaft change in angle, varnish doesn't let it happen, will get a code.