I spent 4 years workin on early VW's.
The VW Kombi's would catch fire here in our summers......just above the engine compartment door on the inside is a little rubber 'T' piece, that perishes and splits, letting fuel tank vapours into the engine compartment....and when they go to start the thing, the dizzy would ignite the fumes....wooomph.....then see smoke billowing from the upper air vents in the rear 1/4.......many a Kombi died that way.
Another one was in the early Beetles where the insulator matting would come free of the firewall, and get sucked into the fan.....no air for the aircooled engine......siezing it.