1965 CADILLAC DEVILLE

Typical onset: 80,000-150,000 mi or any mileage after 50+ years

Symptoms: Blue smoke on startup that clears after warming, Excessive oil consumption (1 quart per 500-800 miles), Poor idle quality and misfiring when cold, Oil fouling on spark plugs

Fix: Valve guides are bronze and wear oval over decades. Complete valve job includes guide replacement or knurling, new seals, valve grinding, and seat work. Expect 18-24 labor hours with heads off the car. Often discover cracked exhaust valve seats during this work on original heads.

Estimated cost: $2,200-3,800

Typical onset: 100,000+ mi or unknown history

Symptoms: Low compression across multiple cylinders (under 120 psi), Excessive blow-by visible at oil filler cap, Heavy oil consumption even after valve work, Gray-blue exhaust smoke under acceleration

Fix: The 429 uses cast pistons that wear over time, and bores glaze from years of easy driving. Requires full teardown, bore .030 or .040 over, new pistons and rings. Factor 35-45 labor hours for complete disassembly, machine work, and reassembly. Often done alongside bearing replacement since you're already there.

Estimated cost: $4,500-7,200

Typical onset: 120,000+ mi or after extended oil change intervals

Symptoms: Metallic knocking that increases with RPM, Low oil pressure at idle (under 10 psi hot), Rod knock that's loudest on cold start, Metal shavings or glitter in oil pan

Fix: These engines are forgiving but not immortal. Neglected oil changes or running low on oil eventually kills the Babbitt-lined bearings. Requires crankshaft removal, measuring journals, possible turning .010 or .020 under, new bearings. If crank needs grinding, add machine shop time. 30-40 labor hours minimum for proper bearing replacement with crank inspection.

Estimated cost: $3,800-6,500

Symptoms: Transmission fluid leaking from steel lines at radiator, Sudden loss of all gears after line rupture, Rust-through at crimp fittings or mid-line corrosion, Red fluid pooling under front of vehicle

Fix: The steel cooler lines rust through after decades, especially in salt states. When they rupture at highway speed, you lose all fluid in minutes and destroy the transmission. Preventive replacement with new steel or braided stainless lines takes 2-3 hours. If it fails on the road, you're looking at transmission rebuild plus cooler lines.

Estimated cost: $180-350 preventive, $2,200-3,500 after failure

Symptoms: Clunk when shifting from Park to Drive or Reverse, Excessive driveline vibration at idle in gear, Visible separation or cracking of rubber mount, Transmission sitting low or cocked to one side

Fix: Rubber mounts don't survive 60 years. The transmission mount lets the tailshaft move excessively, stressing the driveshaft and cooler lines. Replacement is straightforward but requires supporting the transmission. 1.5-2.5 labor hours depending on access and rust situation.

Estimated cost: $180-320

Symptoms: Hesitation or stumble on acceleration from stop, Raw fuel smell in engine bay, Gas dripping from carburetor throat onto intake, Hard starting when hot due to fuel percolation

Fix: The Rochester 4-barrel carburetors use rubber accelerator pump diaphragms and check valves that deteriorate with age and ethanol fuel. Full carburetor rebuild with kit, ultrasonic cleaning, and proper adjustment takes 4-6 hours for proper work. Many shops slap in a kit without proper cleaning and have comeback issues.

Estimated cost: $450-850

Typical onset: 100,000+ mi

Symptoms: Rattling from front of engine on cold start, Erratic timing that won't stay adjusted, Poor idle quality and reduced power, Check timing and it's retarded 8-12 degrees despite setting it correctly

Fix: The original timing sets used nylon-coated cam gears that shed material over decades. Chain stretches from years of use. Requires front cover removal, new double-roller timing set installation. 6-8 labor hours including gaskets and proper reassembly. Always replace the oil slinger and verify oil pump condition while you're in there.

Estimated cost: $650-1,100