The 1979 AMC Concord is built on AMC's robust unitized platform with proven inline-six engines, but age-related mechanical fatigue and parts scarcity are your main enemies now. These cars survive when core drivetrain components are properly maintained, but defer major work and you'll face expensive bottom-end rebuilds.
Lower End Engine Failure (Rod/Main Bearing Wear)
Common · high severityTypical onset: 120,000-180,000 mi
Symptoms: Deep knocking on cold start that fades slightly when warm, Low oil pressure at idle (under 10 psi), Metallic rapping under acceleration, Metal shavings in oil during changes
Fix: Requires full engine teardown to replace main and rod bearings, inspect/machine crank journals, and replace oil pump. Expect 16-22 labor hours for in-chassis rebuild, more if crank needs grinding. Many shops recommend short block replacement instead given age and parts availability challenges.
Estimated cost: $2,800-5,500
Piston Ring Blowby and Cylinder Wear
Common · medium severityTypical onset: 100,000-150,000 mi
Symptoms: Blue smoke on startup and deceleration, Excessive oil consumption (1 qt per 500-800 miles), Crankcase pressure forcing oil past valve cover gaskets, Poor compression readings under 110 psi
Fix: Cylinder bores wear oval on these straight-sixes, especially the 258. Proper fix requires bore/hone and oversized pistons with new rings. Figure 18-24 hours for complete ring job with head work. Many owners opt for reman long blocks at this point given labor costs.
Estimated cost: $2,200-4,200
Torque Converter Lockup Failure (Chrysler TorqueFlite 904/998)
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Shuddering at 35-45 mph cruise, Transmission overheating in highway driving, Poor fuel economy (drop of 3-4 mpg), Slipping sensation during light throttle cruising
Fix: The lockup clutch inside the converter wears and chatters or fails to engage. Transmission must come out for converter replacement. Count on 8-12 hours labor. While out, smart move is full rebuild with updated clutches and bands given age.
Estimated cost: $1,800-3,200
Transmission Mount Collapse
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Excessive drivetrain movement felt through shifter, Vibration at idle in gear, Visible sag of transmission tailhousing
Fix: Rubber deteriorates and the transmission drops, causing harsh engagement and driveline angles that accelerate U-joint wear. Straightforward replacement takes 1.5-2 hours with proper support. Always inspect nearby crossmember for rust damage before ordering parts.
Estimated cost: $180-320
Fuel System Varnish and Carburetor Clogging
Common · medium severitySymptoms: Hard starting after sitting overnight, Rough idle with intermittent stalling, Hesitation on acceleration, Flooding condition with fuel smell
Fix: Ethanol fuel destroys original cork/rubber components and leaves varnish throughout. Complete carb rebuild with ethanol-compatible kit takes 3-4 hours. Replace fuel filter, inspect fuel lines for cracks, and consider in-tank sock filter replacement if tank hasn't been dropped in years. Inline fuel filter should be changed every 10,000 miles on these.
Estimated cost: $380-650
Valve Train Wear and Lifter Noise
Occasional · low severityTypical onset: 80,000-130,000 mi
Symptoms: Ticking/tapping from valve cover area, Noise worse on cold start, may diminish when warm, Occasional valve tick that doesn't quiet with oil change, Rocker arm stud pull-out in severe cases
Fix: AMC sixes use solid rocker pivots that wear, and lifters can collapse with age. Valve adjustment every 30k miles prevents most issues. Full lifter replacement with valve job runs 8-10 hours. Check for worn rocker studs—some engines have threads pull from head requiring thread inserts.
Estimated cost: $850-1,400
Buy only if the engine has documented rebuild history or provable low miles with strong oil pressure—original high-mileage examples are ticking time bombs for expensive bottom-end failures, and parts scarcity makes DIY the only affordable path.
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.