The 1973 Buick Century is a solid mid-size GM A-body with durable engines but typical GM transmission vulnerabilities and rust issues common to this era. The 350 and 455 V8s are workhorses, but emission controls and fuel system degradation after 50 years are the real challenges.
TH-350/TH-400 Transmission Failure
Common · high severityTypical onset: 80,000-120,000 mi
Symptoms: Slipping between gears, especially 1st-2nd, Delayed engagement when shifting into drive, Transmission fluid leaking from cooler lines or pan, Burnt transmission fluid smell
Fix: Complete rebuild typically required. TH-350 (behind 350ci) needs 12-16 hours; TH-400 (behind 455ci) needs 14-18 hours. Includes clutch packs, bands, seals, torque converter inspection. Transmission oil cooler lines frequently corroded and need replacement simultaneously.
Estimated cost: $1,800-3,200
Carburetor and Emission Control System Degradation
Common · medium severitySymptoms: Hard starting when cold or hot, Rough idle and stalling at stops, Black smoke from exhaust, Poor fuel economy below 8 mpg
Fix: Rochester 2-barrel or 4-barrel carbs gum up after sitting. Full rebuild 4-6 hours including cleaning EGR valve, replacing vacuum lines (all hardened by now), checking heat riser valve. Many techs swap to Edelbrock for reliability but that's 8+ hours with tuning.
Estimated cost: $600-1,400
Frame and Subframe Rust Perforation
Occasional · high severitySymptoms: Visible rust holes in frame rails behind front wheels, Subframe mount points crumbling, Creaking or popping sounds over bumps, Uneven tire wear from suspension misalignment
Fix: Common in rust-belt cars. Frame section replacement or boxing requires 20-30 hours of welding fabrication. Many shops won't touch it due to liability. Subframe replacement alone is 12-16 hours. Requires full front suspension removal.
Estimated cost: $3,500-7,000
Intake Manifold Gasket Leaks
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Coolant weeping at intake valley, White smoke on startup, Coolant loss with no visible external leaks, Rough idle from vacuum leaks
Fix: Composite gaskets deteriorate on both 350 and 455. Intake manifold R&R is 6-8 hours. Always replace valley pan gasket, thermostat, and coolant bypass hoses simultaneously. Check for warped intake surface if overheated previously.
Estimated cost: $800-1,400
Rear Main Seal and Oil Pan Gasket Leaks
Common · low severityTypical onset: 70,000-110,000 mi
Symptoms: Oil puddle centered under engine after sitting overnight, Oil coating transmission bellhousing, Oil dripping from rear of oil pan
Fix: Two-piece rope seal (rear main) is notorious for leaking but rarely severe enough to warrant immediate repair. Rear main requires transmission removal, 10-14 hours. Oil pan gasket alone is 4-6 hours including exhaust work and crossmember dropping. Most owners live with minor seepage.
Estimated cost: $650-1,800
Fuel System Degradation (Tank, Lines, Pump)
Occasional · medium severitySymptoms: Fuel smell in cabin or trunk, Fuel starvation under acceleration, Rust particles in fuel filter, Mechanical fuel pump leaking at pushrod
Fix: 50-year-old steel fuel lines rust through, especially near frame mounts. Tank interior rust contaminates system. Full fuel system rehab (tank drop/clean or replace, all lines, pump, filter) takes 8-12 hours. Fuel tank sending unit typically stuck or inaccurate by now.
Estimated cost: $900-1,800
Ignition System Degradation (Points, Distributor)
Common · low severitySymptoms: Intermittent no-start condition, Missing and backfiring under load, Difficulty starting when hot, Loss of power above 3,000 rpm
Fix: Points-type ignition wears bushings in distributor shaft causing timing drift. Distributor rebuild 3-4 hours or swap to HEI (High Energy Ignition) from later GM vehicles, 2-3 hours. HEI swap is better long-term solution and improves reliability significantly.
Estimated cost: $300-700
Buy it if rust-free and transmission shifts clean; budget $3,000-5,000 for deferred maintenance on any barn-find example, but the bones are solid and parts are cheap.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.