What goes wrong with a Datsun 240Z?

I've documented every nut and bolt on multiple 240Z restorations since 2010. The car's failure modes are well-understood and mostly addressable — but rust is the one variable that determines whether a Z is worth buying at all, and it must be evaluated in person before any money changes hands.

Rust: The Deal-Breaker

No other issue on a 240Z comes close to rust in cost and complexity. The critical zones are:

• Frame rails: The main unibody rails on either side of the car. Rust here is structural — expensive to repair correctly and impossible to hide from an informed inspector.
• Floor pans: Virtually every survivor has some floor pan rust. Replacement pans are available from vendors including Motorsport Auto and are DIY-installable with patience.
• Front strut towers: Where the MacPherson strut bolts to the unibody. Rust here compromises suspension geometry and requires welding by someone who knows Z chassis geometry specifically.
• Rocker panels: External but structurally significant on the Z's unibody. Surface rust is manageable; through-rust requires panel replacement.
• Spare tire well: The first place water typically pools. A rotted spare tire well usually means the adjacent rear frame rails are compromised as well.

Carburetion

The twin SU carburetors (HS-type on 1970–1972 cars) are straightforward when properly synchronized but frustrating when out of sync or worn. Rebuilding the diaphragms, needles, and seats is a weekend job with a rebuild kit ($80–$120 per carb). Many owners convert to Weber DCOE sidedrafts — better performance and simpler adjustment, but a departure from originality that affects collector value.

Suspension Bushings

Original rubber suspension bushings are degraded on every unrestored 240Z. Urethane replacements from Energy Suspension or Prothane cost $150–$300 for a complete set and transform the car's handling precision. Rear differential mounts also deteriorate and affect wheel alignment under load — check these at inspection.

Engine Notes

The L24 straight-six is genuinely reliable when the cooling system is maintained, valve clearances are adjusted every 30,000 miles, and oil is changed regularly. Head gasket failure is uncommon on healthy engines; the typical culprits are overheating from neglected coolant or sludging from extended oil change intervals. On any unknown Z engine, run a compression test first — healthy L24s read 170–185 psi, even across all six cylinders.