1971 PONTIAC GTO JUDGE

Typical onset: 80,000-150,000 mi original, or anytime after hard use/deferred oil changes

Symptoms: Heavy knocking from crankcase at idle that worsens under load, Oil pressure dropping below 10 psi at hot idle, Metal shavings in oil pan during changes, Sudden catastrophic failure if bearing fragments wedge

Fix: Requires full engine removal (12-16 hours), crankshaft removal, inspection and possible machining (0.010"-0.030" undersize common), new main and rod bearings, and reassembly. If crank is scored beyond 0.030" undersize, expect crankshaft replacement ($800-1,500 for core exchange). Many shops recommend full rebuild at this point given tear-down labor already invested.

Estimated cost: $4,500-8,500

Typical onset: 100,000+ mi, or sooner with improper tuning/overheating history

Symptoms: Blue smoke on startup that clears after warmup, Excessive crankcase pressure—oil filler cap pops off, Oil consumption over 1 quart per 500 miles, Poor compression readings—variance over 15% between cylinders

Fix: Engine removal (12-16 hours), complete disassembly, cylinder boring typically 0.030" oversize, deck surfacing, new pistons, rings, and full gasket set. Pontiac blocks can usually handle 0.060" overbore maximum. Most owners opt for complete rebuild given labor costs—includes valve job, cam bearings, timing set.

Estimated cost: $6,000-12,000

Typical onset: 70,000-120,000 mi, accelerated by towing or racing

Symptoms: Delayed engagement when shifting into drive or reverse, Harsh 1-2 and 2-3 upshifts under throttle, Slipping in second gear under load, Transmission fluid dark brown or burnt smell

Fix: TH400 rebuild requires removal (6-8 hours), complete disassembly, new clutch packs, bands, seals, torque converter inspection or replacement. These are robust transmissions but 50-year-old friction materials fail. Includes new modulator valve, filter, and external cooler lines inspection.

Estimated cost: $2,200-3,800

Symptoms: Clunking when shifting from park to drive, Excessive driveline vibration at 45-65 mph, Transmission tail housing sitting visibly low, Harsh engagement into gear

Fix: Transmission mount replacement requires supporting transmission, removing crossmember bolts (2-3 hours total). Original rubber mounts deteriorate after decades. Polyurethane upgrades available but transmit more NVH. Inspect tailshaft bushing and output shaft seal while accessible.

Estimated cost: $250-450

Symptoms: Hard starting after sitting—requires multiple cranking attempts, Stumbling or dying at idle when warmed up, Flooding—raw fuel smell and black smoke, Poor throttle response and flat spots during acceleration

Fix: Rochester Quadrajet requires removal (1-2 hours), complete disassembly, ultrasonic cleaning, new gaskets, needle/seat, accelerator pump, and float adjustment. Fuel filter replacement mandatory. Fuel tank often contains decades of varnish—plan for tank removal, cleaning or replacement ($400-800 additional). Fuel lines should be inspected for internal deterioration.

Estimated cost: $600-1,400

Typical onset: 80,000+ mi or unknown history

Symptoms: Loss of low-end torque and throttle response, Backfiring through carburetor on acceleration, Rough idle with timing set correctly by marks, Rattling from timing cover on cold starts (rare but catastrophic if chain breaks)

Fix: Timing cover removal, replacement of chain, gears, and damper (8-10 hours including setting cam timing with degree wheel for Ram Air profile). Original nylon-toothed cam gears shed teeth over time. Should include new water pump, harmonic balancer inspection, and front seal replacement while accessible.

Estimated cost: $1,200-2,000