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Chevrolet 292 Inline-6 Engine Guide - Square Body Trucks

AI
SquareBodyAI
• 9 min read • Updated 3 days, 15 hours ago

Overview

The Chevrolet 292 cubic inch inline-6 engine was a heavy-duty workhorse option available in Square Body trucks from 1973-1987, primarily found in C20/C30 and K20/K30 models. This cast-iron, overhead valve engine produced approximately 165-170 horsepower and 275-290 lb-ft of torque, making it ideal for commercial and heavy-duty applications where reliability and low-end torque were more important than outright performance.

The 292 was part of GM's "Stovebolt Six" family and shared many components with the smaller 250 inline-6. It featured a 4.00" bore x 3.875" stroke and was designed as a cost-effective alternative to V8 engines in fleet and work truck applications. While not as common as the 250 or 305 V8, the 292 has developed a loyal following among Square Body enthusiasts for its durability and unique character.

Key Applications:
- Primarily C20/C30 and K20/K30 trucks (3/4-ton and 1-ton)
- Some C10/K10 models (typically fleet/commercial orders)
- Suburban 20/2500 series
- Limited availability in K5 Blazer (rare)

Common Issues

Carburetor Problems

The Rochester 1-barrel carburetor (model 1ME or E2ME depending on year) is prone to:
- Flooding due to worn needle and seat
- Poor idle quality from clogged idle circuits
- Hesitation caused by accelerator pump diaphragm failure
- Vapor lock in hot weather due to carburetor placement

Cooling System Issues

  • Radiator inadequacy - Many 292 trucks came with marginal cooling capacity
  • Water pump failure - Bearing wear and impeller corrosion common after 100k miles
  • Thermostat housing cracking - Cast iron housing prone to freeze damage
  • Head gasket seepage - Not catastrophic failure, but weeping around cylinders 5-6

Ignition System Problems

  • Points-based systems (1973-1974) require frequent adjustment
  • HEI distributor issues (1975+) including module failure and worn advance mechanisms
  • Spark plug fouling in cylinder #6 due to oil seepage

Oil System Concerns

  • Rear main seal leakage - Common with age, requires transmission removal
  • Valve cover gasket seepage - Long valve cover makes even distribution difficult
  • Oil pressure sending unit failure - Located behind distributor, difficult access

Parts & Materials Needed

Engine Rebuild Components

Pistons: Sealed Power H617CP or Federal Mogul 2317CP
Rings: Sealed Power R9467 or Perfect Circle 41617
Rod Bearings: Clevite CB743P
Main Bearings: Clevite MS909P
Cam Bearings: Clevite SH1126S
Timing Chain Set: Cloyes 9-3100 or Edelbrock 7803
Head Gasket: Fel-Pro 8548PT or Victor Reinz 54039
Valve Set: Sealed Power 2082 (intake) / 2083 (exhaust)

Carburetor Rebuild

Rochester 1ME Kit: Standard Motor Products 432A
Rochester E2ME Kit: Standard Motor Products 1556
Fuel Pump: Carter M60473 or AC Delco 40972
Fuel Filter: AC Delco GF61P

Cooling System

Radiator (2-row): Champion CC161 or Griffin 1-55202-X
Water Pump: Gates 42009 or AC Delco 251-712
Thermostat: Stant 13358 (180°F) or 13359 (195°F)
Fan Clutch: Hayden 2747 or Four Seasons 36712

Ignition System

HEI Distributor: AC Delco D465 (remanufactured)
Ignition Module: AC Delco D1906 or Wells DR108
Spark Plugs: AC Delco R44T or Champion RN12YC
Plug Wires: AC Delco 9748Q or Taylor 79253

Step-by-Step Guide

Basic Tune-Up Procedure

1. Spark Plugs and Wires

  1. Remove air cleaner and mark plug wire positions
  2. Remove wires by twisting and pulling on boots, never the wire
  3. Clean around spark plug wells with compressed air
  4. Remove plugs with 5/8" spark plug socket
  5. Gap new plugs to 0.035" for HEI systems (0.030" for points)
  6. Install plugs hand-tight plus 1/4 turn with socket
  7. Apply dielectric grease to plug wire boots before installation

2. Distributor Service

  1. Remove distributor cap and rotor
  2. Check advance mechanisms by rotating distributor shaft
  3. Inspect HEI module connections for corrosion
  4. Clean distributor cap terminals with fine sandpaper
  5. Check rotor for burning or carbon tracking
  6. Replace pickup coil if engine has intermittent ignition issues

3. Carburetor Adjustment

  1. Warm engine to operating temperature
  2. Connect tachometer to HEI tach terminal
  3. Adjust idle speed screw to 600 RPM (manual) or 650 RPM (automatic)
  4. Turn idle mixture screw clockwise until engine stumbles
  5. Back out mixture screw until highest RPM is achieved
  6. Readjust idle speed if necessary

Carburetor Rebuild Procedure

Removal and Disassembly

  1. Remove air cleaner and disconnect throttle linkage
  2. Disconnect fuel line, vacuum lines, and choke connections
  3. Remove carburetor mounting nuts (7/16" wrench)
  4. Clean exterior thoroughly before disassembly
  5. Remove float bowl screws and carefully lift float assembly
  6. Document jet sizes and positions with photos

Critical Rebuild Steps

  1. Float Adjustment: Set float level to 1/4" from gasket surface
  2. Accelerator Pump: Install new pump cup with lip facing down
  3. Needle and Seat: Use new viton-tipped needle for ethanol compatibility
  4. Power Valve: Test with vacuum pump - should hold 8" Hg minimum
  5. Choke Adjustment: Set to one lean mark for most climates

Year/Model Differences

1973-1974: Early Production

  • Points-based ignition with mechanical advance only
  • Rochester 1-barrel carburetor (Model MV)
  • Lower compression ratio (8.0:1) for regular fuel
  • Mechanical fuel pump with glass bowl filter
  • Cast iron intake manifold integral with head

1975-1980: Mid-Production

  • HEI ignition system introduced - major reliability improvement
  • Rochester 1ME carburetor with feedback control (California)
  • Catalytic converter required - affects exhaust system routing
  • EGR system added for emissions compliance
  • Compression ratio maintained at 8.0:1

1981-1987: Late Production

  • Computer-controlled carburetor (E2ME) with mixture control solenoid
  • ESC (Electronic Spark Control) knock sensor system
  • Improved head design with better port flow
  • Serpentine belt option on some late models (rare)
  • Throttle body injection considered but never implemented

Model-Specific Applications

C20/C30 Series (Most Common)

  • Standard equipment in base trim levels
  • Paired with 4-speed manual (SM465) or 3-speed automatic (TH400)
  • 3.73 or 4.10 rear axle ratios typical
  • Heavy-duty cooling package usually included

K20/K30 4WD Models

  • Same engine specifications as 2WD versions
  • NP205 transfer case most common
  • Front axle engagement may affect idle quality due to additional load
  • Skid plate protection available for oil pan

Suburban 2500 Series

  • Identical engine to pickup applications
  • Longer exhaust system routing required
  • Auxiliary transmission cooler recommended for heavy loads
  • Rear A/C option affects belt routing and cooling load

Tips & Best Practices

Performance Modifications

  • Clifford intake manifold allows 2-barrel carburetor upgrade (+15-20 HP)
  • Header installation requires custom fabrication but improves breathing
  • HEI distributor upgrade essential for pre-1975 engines
  • Electric fuel pump conversion eliminates vapor lock issues
  • Aluminum radiator upgrade dramatically improves cooling capacity

Maintenance Best Practices

  • Change oil every 3,000 miles - these engines are hard on oil
  • Use 10W-30 conventional oil - synthetics may increase seal leakage
  • Flush cooling system annually - cast iron engines prone to rust
  • Keep RPM under 4,000 - these are torque engines, not rev engines
  • Check valve adjustment every 12,000 miles - solid lifter engines require periodic adjustment

Common Mistakes to Avoid

  • Over-tightening spark plugs - cast iron heads are prone to thread damage
  • Using modern ethanol fuel without carburetor modifications
  • Ignoring cooling system maintenance - these engines run hot by nature
  • Attempting performance modifications without addressing cooling first
  • Using incorrect oil viscosity - too thin causes bearing wear, too thick reduces flow

Budget vs. Premium Approaches

Budget Restoration

  • Rebuild existing carburetor with quality kit
  • Refresh HEI distributor with new module and pickup coil
  • Standard replacement radiator with proper capacity
  • OEM-specification rebuild using standard parts

Premium Upgrade

  • Convert to Sniper EFI or similar throttle body injection
  • MSD ignition system with performance distributor
  • Aluminum radiator with electric fans
  • Performance cam and valve train upgrades

Troubleshooting

Hard Starting Issues

Symptoms: Extended cranking, won't start when cold

Diagnosis Steps:
1. Check fuel delivery - remove air cleaner, observe carburetor while cranking
2. Test ignition spark - remove plug, ground to engine, observe spark quality
3. Verify choke operation - choke plate should close when cold
4. Check compression - should be 140-160 PSI across all cylinders

Common Causes:
- Fuel pump failure - mechanical pumps fail gradually
- Carburetor flooding - check float level and needle/seat
- Ignition timing - should be 8-10° BTDC at idle
- Choke adjustment - too lean for cold starts

Poor Idle Quality

Symptoms: Rough idle, stalling, inconsistent RPM

Diagnosis Steps:
1. Connect vacuum gauge - should read 18-22" Hg at idle
2. Check for vacuum leaks using carburetor cleaner spray
3. Test idle mixture adjustment response
4. Verify PCV system operation

Common Causes:
- Vacuum leaks at carburetor base or intake manifold
- Carburetor idle circuits clogged with varnish
- EGR valve stuck open causing lean condition
- Ignition timing incorrect or advance mechanism failure

Overheating Problems

Symptoms: Temperature gauge in red, coolant loss, steam

Diagnosis Steps:
1. Check coolant level when cold
2. Test radiator cap pressure rating (15 PSI)
3. Verify thermostat opening temperature
4. Inspect water pump for leakage or bearing play
5. Check fan clutch engagement when hot

Common Causes:
- Inadequate radiator capacity - upgrade to 3-row or aluminum
- Water pump impeller corrosion - common in neglected systems
- Thermostat failure - stuck closed or wrong temperature rating
- Fan clutch failure - won't engage when engine gets hot
- Head gasket seepage - combustion gases entering cooling system

Oil Pressure Issues

Symptoms: Low oil pressure warning, gauge reading low

Diagnosis Steps:
1. Verify oil level and condition
2. Test with mechanical gauge at oil pressure sending unit
3. Check oil pump pickup screen for debris
4. Measure bearing clearances if pressure consistently low

Common Causes:
- Oil pressure sending unit failure - very common, easy fix
- Worn main or rod bearings - requires engine rebuild
- Oil pump wear - high mileage engines common
- Clogged oil pickup screen - from neglected oil changes

Performance Loss

Symptoms: Reduced power, poor acceleration, low top speed

Diagnosis Steps:
1. Perform compression test - should be within 10% cylinder to cylinder
2. Check exhaust restriction with back-pressure gauge
3. Verify carburetor accelerator pump operation
4. Test ignition advance mechanisms

Common Causes:
- Carburetor accelerator pump failure - no response to throttle input
- Exhaust restriction - collapsed internal baffles or clogged catalytic converter
- Ignition timing retarded or advance mechanism stuck
- Valve adjustment incorrect - these engines require periodic adjustment
- Air filter restriction - often overlooked maintenance item