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What Are the Head Bolt Torque Specifications on a 1991 Pontiac Sunbird?

Updated February 21, 2017

As standard equipment, Pontiac installed the 2.0 litre four-cylinder engine into the 1991 Sunbird. As optional equipment, the more powerful 3.1 litre six-cylinder was available. The 2.0 litre engine featured a single-cylinder head. Because the 3.1 litre is a "V" design engine, it features two cylinder heads. Between the cylinder heads and the engine block is a gasket, which typically fails if the engine overheats. Replacing the gasket is fairly straightforward, but care must be taken to properly tighten the head bolts upon reassembly to avoid damaging the engine.

2.0 Four-Cylinder

The head bolts must be tightened in a specified order. It is therefore important to identify each head bolt. Locate the bolt at the front of the driver's side of the cylinder head. That bolt is bolt number 10. Working toward the back of the driver's side of the cylinder head from bolt number 10 are bolt number 6, 2, 4 and 8. Locate the bolt at the front of the passenger's side of the cylinder head. That bolt is bolt number 9. Working towards the back of the passenger's side of the cylinder head from bolt number 9 are bolt numbers 5, 1, 3 and 7.

It is important to tighten the cylinder head bolts in order to prevent warping the cylinder head or damaging the head gasket. Tighten each cylinder head bolt to 18 foot-pounds of torque with a torque wrench in numerical order starting with bolt number 1 and ending with bolt number 10.

The final tightening process relies on gradual tightening increments with a wrench to ensure the head gasket seats properly. Only tighten the head bolts in their numerical order. Tighten each head bolt 60 degrees. Tighten each head bolt an additional 60 degrees. Tighten each head bolt 15.6 degrees Cor a third time. Finally, tighten each bolt an additional 40 degrees to complete the process.

3.1 Six-Cylinder

The head bolts must be tightened in a specified order. It is therefore important to identify each head bolt. Locate the bolt at the front of the driver's side of the cylinder head. That bolt is bolt number 5. Working toward the back of the driver's side of the cylinder head from bolt number 5 are bolt number 1, 4 and 8. Locate the bolt at the front of the passenger's side of the cylinder head. That bolt is bolt number 6. Working towards the back of the passenger's side of the cylinder head from bolt number 6 are bolt numbers 2, 3 and 7.

It is important to tighten the cylinder head bolts in order to prevent warping the cylinder head or damaging the head gasket. Tighten each cylinder head bolt to 33 foot-pounds of torque with a torque wrench in numerical order starting with bolt number 1 and ending with bolt number 8.

Unlike the 2.0 litre engine, only a single final tightening is required. Tighten each bolt in its numerical sequences 90 degrees.

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About the Author

John Stevens has been a writer for various websites since 2008. He holds an Associate of Science in administration of justice from Riverside Community College, a Bachelor of Arts in criminal justice from California State University, San Bernardino, and a Juris Doctor from Whittier Law School. Stevens is a lawyer and licensed real-estate broker.