Buy a Ferrari 400i on a rust-free shell and a fuel-injected V12 that idles clean when warm. Rotten sills, a lazy automatic and drifting K-Jetronic parts can cost more than the car looks worth.
For this November 5, 2026 guide I read Car Collector International: Ferrari 400 buyer's guide and Unique Cars: Ferrari 400i (1979-84) buyer's guide. The mechanical cautions below come from those pages; the order of checks and the questions for the seller are my own practical recommendations. Any price figures in those sources are market snapshots, not a valuation of the car in front of you. So, compare it with recent sales of the same specification and condition. I also kept the advice to things you can see, hear or ask for on a viewing day.
Get the shell on a hoist
Unique Cars says these Ferraris rust as readily as Fiats or Lancias of the same age and calls a hoist check of floors and sills mandatory, with lower doors and arches next. Car Collector International adds the front-boot floor, rear arches and valance. Spare panels are scarce. Treat every bubble as a cost.
Watch the V12 warm up
Unique Cars says a warm 400i should show about 35 to 40 psi oil pressure at idle and respond at once. Car Collector International lists uneven warm idle, cold hesitation and warm-up regulator faults as signs of K-Jetronic drift. Ask for compression and leak-down on all twelve cylinders.
Check the engine is the right one
Car Collector International says some cars carry replacement V12s from 365 GT4 or 412 donors. It suggests checking the engine number, fuel system spec and block casting date. A swapped engine is a value change. Ask before you travel.
Drive the GM automatic properly
Unique Cars calls the GM400 one of the best automatics made, though kickdown from low revs can stutter. Ask about fluid changes. Our cold-start test guide helps you plan the first start of the day. A slipping shift or late engagement needs a transmission shop opinion.
Try the air-con and electrics
Car Collector International says the air-con is rarely fully working without service and flags connector corrosion behind the dash and at the headlamp bowls. Unique Cars says the headlamps should rise quickly. Test every circuit. Plan for loom work on a stored car.
Check the front spoiler and trim
Unique Cars warns that dents, cracked lenses and crazed chrome can all be major costs because parts are scarce. Look closely at the front spoiler. Interior leather is costly too. Make a list before you talk price.
Prove the identity before a deposit
Match the chassis number on the 400i to the title, any import papers and the plate on the car before you order a history report. Our VIN verification guide walks through that match, and imported-car report coverage sets expectations for cars that spent years overseas. Older chassis numbers may sit outside modern report databases, so confirm coverage before paying. NMVTIS covers U.S. title history only; it cannot replace foreign records or a physical inspection.
Get the repair scope in writing first
If the sills are soft or the warm idle hunts, get a Ferrari specialist's written estimate before you commit. These cars look affordable on paper, and the first big bill usually arrives within the first year of ownership. Look, a seller PDF or a folder of photos is a starting document, not independent proof of condition. Ask the inspector for written findings with local estimates, split into safety work and cosmetic wishes. The NYC consumer-agency used-car guidance tells buyers to have an independent mechanic check the car, and our pre-purchase inspection checklist helps you set the scope. Keep a dated note of the drive, the temperatures and any noises, because a seller who disputes your findings later will ask what you saw and when.
We are a licensed CARFAX and AutoCheck reseller, not affiliated with CARFAX, AutoCheck or Experian. Guest reports have been about $5.50, member reports about $4.50 and a two-report bundle about $6.75; confirm the price at checkout because it can change. A report can miss unreported work, so keep the inspection appointment even when the history looks quiet.
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