Porsche M28 (928 V8)

Porsche's front-mounted V8 — the M28 — in the 928, from 4.5 to 5.4 litres.

It is the engine of the car meant to replace the 911, and it is as different from one as an engine can be: water-cooled, all-aluminium, at the front, driving a rear transaxle. Nothing in Porsche's flat-six experience transfers.

⚑ The timing belt is the thing that ends these engines, and the later 32-valve versions are interference designs. On a car this old with unknown history the belt and its tensioner are the first question, and the tensioner is the part that actually fails.

Its other items are age and heat: the plastic coolant crossover pipes, the engine wiring loom on 1980s cars, and oil leaks from seals long past their design life.

Parts and specialists exist but are concentrated, and the cars are cheap enough relative to the work that a belt service decides many of them.