IF you know the hail is coming and must park outside, try strapping mattresses and couch cushions and folded blankets and spare kids to roof and hood and windshield area.
Yeah; that sound means the thrummalator has failed and put the moneysucker into overdrive. Unfortunately the thrummalator is NLA, so eventually the whole truck will explode. Best I take it now, before someone gets hurt. What’s the address?
Oh yeah on the first note above...
On the second, I would say do what PM you can on the engine before it goes in, as you can reach a lot more now than you can later, and with a lot less cussing and fewer scraped knuckles (PHH, anyone?). Then do any engine bay PM when the original block comes...
Exactly what I'm doing, but installing a low(er) mileage and doing a slo-mo / slow-cost rebuild on the high. Never hurts to have a spare engine on hand...
I had a misfire issue once on #6; new plugs and wires fixed it. When I started up, it felt like the whole truck was coming apart; I called a tow to get home--four blocks away. Not sure I'd have noticed the presence/absence of a knock, and I sure wouldn't wanna do that six times... Maybe my...