Acura NSX NA1

A hand-built 3.0-litre DOHC-VTEC V6 that set benchmarks in 1990: aluminium cylinder head, hand-fitted titanium-coated valves, free-revving to 8000 rpm. Its character lives from the clean, mechanically precise response and the famous VTEC crossover at around 5800 rpm, where the sound flips from silky to a hard, bright edge. Demanding to maintain: solid lifters with no hydraulic compensation require periodic valve-clearance adjustment, or tight valves and burnt exhaust valves loom. As an interference engine with a timing belt, a snapped belt destroys the head, so the interval is sacred. Treat the maintenance seriously and you get one of the most durable and emotional high-revving naturally aspirated engines ever produced — a cult unit whose fascination lies in mechanical finesse, not raw power.

• !! Timing belt — interference engine, costly interval from 145,000 km

  The timing belt must be replaced every 90,000 miles or 6 years. As an interference engine, a belt failure causes valve-to-piston contact that destroys the cylinder head. The job is labor-intensive (about 7 hours); the water pump is best replaced at the same time.

  Symptoms: Usually no warning; on failure the engine stops abruptly with no compression afterward and bent, rattling valves.
  1,400–2,800 $
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• !! Crankshaft pulley (harmonic balancer) delamination from 130,000 km

  The pulley consists of two steel sections bonded with a rubber damper. The rubber hardens and disintegrates with age, letting the outer ring separate. Loose pieces can slice through the timing belt cover and damage the valvetrain timing.

  Symptoms: Rattle or wobble from the pulley, belt squeal, visibly runout outer ring and in extreme cases a thrown ring.
  250–600 $
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• !! Snap ring transmission failure (1991-1992) from 80,000 km

  On transmissions numbered J4A4-1003542 to J4A4-1005978 (MY 1991-1992) a groove was machined too wide. The snap ring holding the countershaft twists and shatters; metal fragments circulate and can destroy the gearbox.

  Symptoms: Shifter moves back and forth in 1st/2nd gear under acceleration or braking, followed by a loud crunch or grinding with no warning.
  2,300–7,000 $
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+ 2 more engine weaknesses + vehicle weaknesses

The bored-out 3.2-litre evolution of the original V6, refined with fibre-reinforced cylinder liners (FRM) and paired from the factory with a longer sixth gear. The DOHC-VTEC spins silkily past 8000 rpm and above the VTEC threshold delivers one of the most precise high-rev surges in the naturally aspirated segment — the sound change still raises goosebumps. In character the engine is undramatically reliable as long as the maintenance is right: interference timing belt with a fixed interval, solid-lifter valve adjustment, and the aging rubber damper on the crankshaft pulley all want attention. Keep on top of those and you have an engine of eternal character — high-revving, silky, mechanically honest. A masterpiece of Japanese hand-assembly that technically underpins the model's reputation as an everyday supercar.

• !! Timing belt — interference engine, fixed interval from 140,000 km

  Timing belt replacement every 90,000 miles or 6 years is mandatory. As an interference engine, a belt failure causes valve-to-piston contact and severe head damage. The water pump is best replaced at the same time; 1997+ pumps have a relocated weep hole.

  Symptoms: No warning; on failure the engine stops abruptly with no compression and bent valves.
  1,500–3,000 $
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• !! Crankshaft pulley ages and separates from 130,000 km

  The rubber damper between the inner and outer ring of the pulley hardens with age and can break down. The outer ring migrates or separates, can slice through the timing belt cover and disrupt valve timing. Replacement is recommended roughly every 9 years.

  Symptoms: Pulley wobble or rattle, belt squeal and a visibly runout outer ring.
  250–600 $
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• !! Valve clearance adjustment — solid lifters from 90,000 km

  Solid lifters require periodic valve clearance adjustment by screw and locknut. Tight clearance prevents proper valve seating and can cause misfires and burnt exhaust valves. Adjustment is done cold.

  Symptoms: Valvetrain ticking when cold, rough idle, power loss and possible misfires.
  300–700 $
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+ 1 more engine weaknesses + vehicle weaknesses