Direct answer: every unrestored 240Z carries rust in the floors and rails, doglegs and rockers, rear quarters, battery tray, fender bottoms and hatch surround — thin-gauge steel, minimal factory rust-proofing and moisture-trapping box sections guarantee it. Because the S30 is a unibody, these aren't cosmetic repairs: the panels are the structure.
The big seven
Floors and frame rails: check from below at the seat mounts and where rails meet the floor — rot here changes how the car drives.
Doglegs and rockers: the classic S30 failure; probe behind the rear of the sill.
Rear quarters and arches: bubbling at the arch lip means the inner structure is involved.
Battery tray and cowl: acid and trapped leaves eat the tray, the apron below it and the cowl corners — the reproduction battery holder area panels fix what's almost always rotten.
Front fender bottoms: around the headlight buckets and the lower rear corner; bolt-on reproduction fenders solve what patching can't.
Hatch surround and taillight panel: hardened seals soak the slam panel and taillight surround.
Spare wheel well: the lowest point of the shell collects everything.
Unibody means structural
There is no frame under a 240Z — the pressed panels carry every load. Repairs must be welded at factory seams with correct-profile steel: butt-welded patches and full pressings at original spot-weld locations, never lap-overs, and never structural sections 'repaired' with filler. If you're not an experienced welder, this is professional work; the car's crash behaviour depends on it.
Restoration economics
Concours 240Zs have passed into six figures, which changed the maths: work that was uneconomic a decade ago is routine now. Correct-profile reproduction pressings — hood, fenders, structural sections — cost a fraction of hand-formed steel and fit the factory seams. Many pressings carry to the 260Z with detail differences at flanges and trim holes; compare before committing on a later S30.
After the metal
Epoxy prime everything, seam-seal as the factory did, and get cavity wax into every box section — the S30's design still traps moisture, and the second restoration is always more expensive than the wax.
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