GMC Jimmy 1970-1991 6.2L Engine Bolt Torque Specifications & Fastener Values
GMC Jimmy 1970-1991

GMC Jimmy 1970-1991 6.2L Engine Bolt Torque Specifications

Comprehensive guide to the bolt torque specifications for the 6.2L engine in the 1970-1991 GMC Jimmy. Includes detailed torque values for cylinder heads, main bearings, connecting rods, and more.

Updated

Important Information

Safety guidelines and reference information for proper torque application

Quick Reference Guide
ft-lbs → Nm
× 1.356
ft-lbs → kg-m
× 0.138
Nm → ft-lbs
× 0.738
in-lbs → ft-lbs
× 0.083

Common Torque Patterns

Star Pattern

Used for wheels and other circular bolt patterns

Star Pattern torque pattern diagram showing proper bolt tightening sequence
Cross Pattern

Used for gaskets and cover plates

Cross Pattern torque pattern diagram showing proper bolt tightening sequence
Sequential Pattern

Used for head bolts and other critical components

Sequential Pattern torque pattern diagram showing proper bolt tightening sequence

Common Mistakes to Avoid

Over-tightening

Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.

Prevention:

Always use a calibrated torque wrench and follow specifications exactly.

Incorrect Torque Sequence

Tightening bolts in the wrong order can cause uneven pressure distribution and potential leaks or damage.

Prevention:

Follow the manufacturer's specified torque sequence pattern.

Dirty Threads

Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.

Prevention:

Clean and inspect all threads before assembly. Use new thread locker if specified.

Reusing TTY Bolts

Torque-to-yield bolts are designed to stretch and must not be reused.

Prevention:

Always replace TTY bolts with new ones. They are single-use only.

Dry vs. Lubricated

Not accounting for whether torque specs are for dry or lubricated fasteners can lead to incorrect tension.

Prevention:

Check if specs are for dry or lubricated threads. Use specified lubricant when required.

Recommended Tools

Torque Wrench (1/4" Drive)

Range: 2-25 ft-lbs
Small fasteners, delicate components

Torque Wrench (3/8" Drive)

Range: 10-100 ft-lbs
Most common automotive fasteners

Torque Wrench (1/2" Drive)

Range: 30-250 ft-lbs
Large fasteners, wheels

Angle Gauge

Torque-to-yield (TTY) bolts

Torque Wrench Care

  • Calibrate annually or after 5,000 clicks
  • Store at lowest setting
  • Keep clean and lubricated

Search Specifications

Search by component name, bolt size, or description

Torque Calculator

Convert between different torque units

Cylinder Head

Components related to the cylinder head, including bolts for securing the head to the engine block, rocker arms, and valve covers.

1

Cylinder Head Bolts (Initial)

M12 x 1.5
Important Notes
Initial torque for seating the cylinder head. Follow the manufacturer's torque sequence.
2

Cylinder Head Bolts (Final)

M12 x 1.5
Torque Value
70 ft-lbs (95 N·m)
Important Notes
Final torque to ensure proper clamping force and head gasket sealing. Estimated value based on similar engines.
3

Valve Cover Bolts

M6 x 1.0
Torque Value
9 ft-lbs (12 N·m)
Important Notes
Ensures a proper seal for the valve cover. Estimated value based on similar engines.
4

Rocker Arm Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures the rocker arms to the cylinder head. Estimated value based on similar engines.

Crankshaft And Bearings

Components related to the crankshaft, including main bearing caps, connecting rods, and harmonic balancer.

1

Main Bearing Bolts

M12 x 1.5
Torque Value
100 ft-lbs (136 N·m)
Important Notes
Secures the main bearing caps to the engine block. Follow the manufacturer's torque sequence.
2

Connecting Rod Nuts

M10 x 1.25
Torque Value
47 ft-lbs (64 N·m)
Important Notes
Secures the connecting rod to the crankshaft. Estimated value based on similar engines.
3

Crankshaft Pulley/Harmonic Balancer Bolt

M16 x 1.5
Torque Value
75 ft-lbs (102 N·m)
Important Notes
Secures the harmonic balancer to the crankshaft. Estimated value based on similar engines.

Intake And Exhaust

Components related to the intake and exhaust manifolds, including bolts for securing manifolds and associated components.

1

Intake Manifold Bolts

M8 x 1.25
Torque Value
30 ft-lbs (41 N·m)
Important Notes
Ensures a proper seal between the intake manifold and cylinder head. Follow the manufacturer's torque sequence.
2

Exhaust Manifold Bolts

M8 x 1.25
Torque Value
30 ft-lbs (41 N·m)
Important Notes
Secures the exhaust manifold to the cylinder head. Follow the manufacturer's torque sequence.

Oil System

Components related to the oil system, including oil pan, oil pump, and oil drain plug.

1

Oil Pan Bolts

M6 x 1.0
Torque Value
13 ft-lbs (18 N·m)
Important Notes
Ensures a proper seal between the oil pan and engine block. Follow the manufacturer's torque sequence.
2

Oil Drain Plug

M14 x 1.5
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Secures the oil drain plug to the oil pan. Estimated value based on similar engines.

Troubleshooting Guide

Common issues, diagnostic steps, and prevention guidelines

Common Issues

Bolt stretching, stripped threads, uneven torque patterns

Loose Components

Symptoms:
  • Rattling or vibration noises
  • Visible movement in components
  • Uneven panel gaps
Solutions:
  • Clean threads and mounting surfaces
  • Replace damaged fasteners
  • Apply proper torque in sequence
  • Use thread locker if specified

Stripped Fasteners

Symptoms:
  • Unable to achieve proper torque
  • Fastener spins freely
  • Visible thread damage
Solutions:
  • Use thread repair kit if appropriate
  • Install thread insert (HeliCoil)
  • Replace component if threaded hole is damaged
  • Upgrade to higher grade fastener if recommended

Overtightened Components

Symptoms:
  • Cracked or deformed parts
  • Broken fasteners
  • Compressed gaskets or seals
Solutions:
  • Replace damaged components
  • Use new fasteners
  • Follow proper torque sequence
  • Verify correct torque specifications

Diagnostic Steps

Visual inspection, torque verification, thread assessment

1

Visual Inspection

Inspect the affected area for any visible signs of damage or wear

  • Check for cracks or deformation
  • Look for signs of excessive wear
  • Verify proper fastener installation
2

Torque Verification

Verify the torque applied to the fasteners

  • Check the torque wrench calibration
  • Verify the torque specification
  • Compare the applied torque to the specification
3

Thread Assessment

Assess the condition of the threads

  • Check for signs of thread damage
  • Verify the thread type and size
  • Check for proper thread engagement

Prevention Guidelines

Best practices, maintenance tips, tool care

Best Practices

  • Always follow the recommended torque specification
  • Use the correct type and size of fasteners
  • Verify the torque wrench calibration regularly

Maintenance Tips

  • Regularly inspect the affected area for signs of wear or damage
  • Replace damaged or worn-out components promptly
  • Keep the work area clean and organized

Tool Care

  • Regularly clean and maintain the torque wrench
  • Store the torque wrench in a dry and secure location
  • Verify the torque wrench calibration before each use

Frequently Asked Questions

Find answers to common questions about torque specifications

Q1

What are the torque specifications for the cylinder head bolts on a 6.2L engine?

The cylinder head bolts on a 6.2L engine should be torqued in three stages: first to 40 ft-lbs, then to 70 ft-lbs, and finally to 100 ft-lbs. Always follow the manufacturer's sequence to avoid warping the cylinder head.

Q2

How often should I check the torque on my engine bolts?

It's recommended to check the torque on critical engine bolts, such as cylinder head and main bearing cap bolts, after the first 500 miles of operation and then periodically during routine maintenance. This ensures they remain within specifications and prevents leaks or component failure.

Q3

Can I reuse head bolts on a 6.2L engine?

No, head bolts on a 6.2L engine are torque-to-yield (TTY) bolts and should not be reused. They are designed to stretch during installation, and reusing them can lead to improper clamping force and potential engine damage.

Environmental Considerations

Temperature, humidity, and seasonal effects on torque specifications

Temperature Effects

Includes: High Heat, Cold Weather, Thermal Cycling

Temperature can significantly impact torque values and fastener behavior

Cold Weather

Effects:
  • Increased material brittleness
  • Higher torque required due to thread contraction
  • Reduced thread lubricant effectiveness
Recommendations:
  • Allow components to warm to room temperature when possible
  • Consider using winter-grade thread lubricants
  • Check torque values more frequently during winter months

Hot Weather

Effects:
  • Thermal expansion of components
  • Decreased friction in threads
  • Accelerated lubricant breakdown
Recommendations:
  • Check torque when components are at normal operating temperature
  • Use temperature-resistant thread lockers
  • Consider re-torquing after heat cycles

Humidity and Corrosion

Covers: Rust Prevention, Salt Exposure, Moisture Control

Moisture and corrosion can affect fastener integrity and torque values

High Humidity

Effects:
  • Accelerated corrosion formation
  • Reduced friction coefficient
  • Potential thread seizing
Prevention:
  • Use corrosion-resistant fasteners
  • Apply appropriate anti-seize compounds
  • Maintain proper protective coatings

Salt Exposure

Effects:
  • Rapid corrosion development
  • Thread damage
  • Seized fasteners
Prevention:
  • Regular underbody washing
  • Use of sacrificial anodes where appropriate
  • Application of protective coatings

Seasonal Maintenance

Spring, Summer, Fall, and Winter maintenance schedules

Spring

  • Inspect for winter damage
  • Clean and protect exposed fasteners
  • Check torque on critical components

Summer

  • Monitor heat-affected components
  • Check expansion-related loosening
  • Inspect cooling system mounts

Fall

  • Prepare for winter conditions
  • Apply corrosion protection
  • Verify all fasteners are properly torqued

Winter

  • More frequent inspection of critical fasteners
  • Check for salt damage
  • Monitor suspension component torque

Related Resources

Tools, service procedures, and technical bulletins

Recommended Tools

Torque Wrench

A precision tool used to apply a specific torque to a fastener such as a bolt or nut.

  • Adjustable torque settings
  • Durable construction for heavy-duty use
Learn more

Socket Set

A set of sockets in various sizes to fit different bolt heads.

  • Includes both metric and standard sizes
  • Compatible with torque wrench
Learn more

Thread Locker

A chemical compound used to secure bolts and prevent loosening due to vibration.

  • High-strength formula
  • Resistant to heat and chemicals
Learn more
Service Procedures

Cylinder Head Bolt Torque Procedure

Detailed steps for properly torquing the cylinder head bolts on a 6.2L engine.

  • Clean the bolt threads and bolt holes thoroughly.
  • Apply a small amount of engine oil to the bolt threads.
  • Install the bolts and tighten them in the specified sequence to the initial torque value.
  • Re-torque the bolts to the final specification in the same sequence.
View full procedure

Main Bearing Cap Bolt Torque Procedure

Steps for torquing the main bearing cap bolts to ensure proper engine assembly.

  • Clean the bolt threads and bearing cap surfaces.
  • Apply thread locker to the bolt threads.
  • Tighten the bolts in the specified sequence to the initial torque value.
  • Re-torque the bolts to the final specification in the same sequence.
View full procedure
Technical Service Bulletins

Engine Bolt Torque Specifications Update

1985-03-15

Updated torque specifications for the 6.2L engine bolts to address issues with bolt loosening.

1970-1991 GMC Jimmy

Resolution: Follow the revised torque specifications and use thread locker as recommended.

Cylinder Head Bolt Failure Advisory

1988-07-22

Advisory regarding potential cylinder head bolt failures due to improper torque application.

1970-1991 GMC Jimmy

Resolution: Ensure proper torque sequence and values are followed during engine assembly or repair.

About the Author

Expert automotive knowledge and experience

Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

Facebook Contact
15+ Years
Experience
500+ Guides
Guides
50+ Makes
Vehicles
1000+ Solutions
Solutions

Diagnostic

Specialized in advanced diagnostic techniques using modern scan tools and oscilloscopes.

Repair

Expert in both traditional mechanical repairs and modern vehicle systems.

Additional Expertise

Documentation

Created over 500 detailed repair guides and technical documents.

Training

Conducted technical training sessions and contributed to repair databases.

Certifications & Research

Certifications

  • ASE Master Technician Certification
  • Advanced Diagnostic Specialist
  • Hybrid/Electric Vehicle Systems
  • Performance Tuning Expert

Research & Community

Actively researches emerging technologies and contributes to automotive forums.

Legal Disclaimer

Important information about using this content

Always refer to your vehicle's service manual and take appropriate safety precautions when performing any maintenance or repairs.

General Information
The information provided on this website is for general informational purposes only. While we strive to maintain accuracy in our content, all specifications, procedures, and technical information should be verified against your vehicle's official service manual or with the manufacturer directly.
Warranty & Liability

The content on this website is provided "as is" without any representations or warranties, express or implied. We make no representations or warranties regarding the accuracy, completeness, or availability of the information.

We shall not be liable for any direct, indirect, special, or consequential damages arising from the use of information on this website.

Technical Information
  • All specifications, including torque values, fluid capacities, and maintenance procedures, should be verified against your vehicle's factory service manual.
  • Vehicle specifications and procedures may vary by model year, trim level, and region.
  • Always follow the manufacturer's recommended procedures and safety precautions.
  • Working on vehicles can be dangerous. Always take proper safety precautions and use appropriate safety equipment.
  • If you're unsure about any procedure, consult a qualified professional mechanic.
Intellectual Property
All content, including text, images, and specifications, is protected by copyright and other intellectual property laws. Any unauthorized use or reproduction is prohibited.

© 2025 GMC Specs. All rights reserved.

Privacy Policy Terms of Service