The 1970 Plymouth Duster is a remarkably durable A-body platform with bulletproof slant-six and small-block V8 options, but 50+ years of age brings predictable wear items around the torsion bar suspension, steering components, and originality-dependent issues with electrical and cooling systems.
Torsion Bar Suspension Component Wear
Common · medium severitySymptoms: Excessive front-end dive during braking, Wandering or vague steering feel, Uneven tire wear on inside edges, Clunking over bumps from worn bushings
Fix: Complete lower control arm rebuild with new bushings (2.5 hours per side), upper ball joints (1.5 hours), strut rod bushings (1 hour). Torsion bars themselves rarely fail but adjusters seize. Most cars need full front-end rebuild at this age regardless of mileage.
Estimated cost: $800-1,400
Timing Chain Stretch (Slant-Six and V8)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Hard starting when hot, Backfiring through carburetor, Loss of power at higher RPM, Rattling noise from timing cover on cold startup lasting 3-5 seconds
Fix: Replace timing chain, gears, and tensioner. On slant-six: 3-4 hours (radiator stays in). On V8: 4-5 hours (often easier to pull radiator). Original chains on unmolested engines are often severely stretched by now. Use double-roller aftermarket set.
Estimated cost: $350-650
Manual Steering Box Wear
Common · medium severityTypical onset: 100,000+ mi
Symptoms: Excessive play at steering wheel (more than 2 inches), Binding or tight spots when turning lock-to-lock, Leaking gear oil from sector shaft seal, Groaning under load during parking maneuvers
Fix: Rebuild with sector shaft kit (3 hours) or replace with reman unit (2 hours). Manual boxes are adjustable but most are worn beyond adjustment specs. Power steering cars face similar issues plus pump/hose leaks adding $200-400.
Estimated cost: $450-750
Single-Wire Alternator System Failure
Occasional · high severitySymptoms: Ammeter shows discharge at idle, Dim headlights at low RPM, Battery repeatedly dying, Burning smell from bulkhead connector, Melted wire insulation at firewall pass-through
Fix: The original ammeter-based charging system runs full current through the bulkhead connector which overheats and creates resistance. Fix requires bypassing bulkhead with dedicated alternator wire (2 hours) or full MAD bypass kit (3-4 hours). This is a fire risk on original wiring.
Estimated cost: $150-400
Carburetor Issues (Carter BBD on Slant-Six, AVS/Holley on V8)
Common · low severitySymptoms: Hesitation on acceleration from stop, High idle that won't adjust down, Flooding and black smoke, Stalling when hot at stop lights, Gas smell in engine bay
Fix: Usually rebuild with quality kit (2-3 hours for Carter BBD, 3-4 for AVS). Accelerator pump wear is universal on these. Ethanol fuel destroys original cork gaskets. Many replaced with Holley replacements that need jetting. Original smog equipment often deleted causing tuning issues.
Estimated cost: $250-500
Upper Radiator Support and Core Support Rust
Occasional · medium severitySymptoms: Radiator sits loose or tilted, Hood alignment issues, Visible rust-through on upper core support, Crack in sheet metal near hood latch area
Fix: Upper core support rusts where water sits against the hood seal. Replacement requires cutting and welding new panel (6-8 hours). Affects radiator mounting and hood fit. Not structural but deteriorates quickly once started. Regional issue - worse in salt states.
Estimated cost: $600-1,200
Fuel Tank and Sender Issues
Occasional · medium severitySymptoms: Fuel gauge reads empty or pegged full constantly, Gas smell near filler neck area, Visible rust staining below tank area, Fuel starvation at 1/4 tank
Fix: Tank straps rust through and tank develops pinhole leaks. Sender units fail internally. Proper fix: drop tank (1.5 hours), replace or have cleaned/sealed, new sending unit, new rubber filler hose. Many tanks have sat with old gas creating varnish buildup.
Estimated cost: $400-800
Absolutely buy one if the body is solid - these are simple, tough cars with cheap parts availability, but budget $2,000-3,000 for deferred maintenance on any survivor regardless of claimed condition.
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.