How to Replace Head Gaskets


It’s not uncommon to have a few inquiries regarding your alternatives while installing a new set of head gaskets. For example, should a copper or graphite gasket be used? What does it signify if the fire rings on the gaskets are pre-flattened? Should you apply a sealant to the gaskets before installing them? These are all excellent questions, and our purpose is to clear up any confusion on the subject.

How to Replace Head Gaskets

We know that combustion temperatures and pressures are quite high (about 2,000°F and up to 1,000psi) and that they can be substantially higher in enhanced applications. However, the head gasket’s purpose is to seal the susceptible gap between the block and head while also guiding and sealing the hot coolant and oil. These are the reasons why it’s critical to have a basic understanding of head gasket designs.

Designs for Head Gaskets

Head gasket constructions are classified into two types: composite and metal. Thin gasket sheets will be connected to a steel core with a fire ring at the cylinder bore in a composite gasket. A metal-type gasket might be made of shim steel, multi-layer steel, or solid copper. Shim steel gaskets, which are entirely stamped steel and come in a range of thickness combinations, are one of the oldest forms of gasket designs. Multi-layered steel (MLS) is a modern design that is made up of two or more embossed stainless sheets molded to flat metalcore. A solid copper design is the final type of metal gasket. Copper is one of the toughest and most conforming metals, and copper-style gaskets provide a wide range of hole and thickness combinations.

When a gasket is touted as having pre-flattened wire rings or “fire rings,” it signifies that the ring-closing combustion chamber has been pre-flattened to reduce surface damage to aluminum heads. Fel-Pro Gaskets provides a variety of MLS pre-flattened steel or copper ring style gaskets.

What Kind of Gasket Should I Use?

We always recommend using gaskets with a soft copper wire ring when installing aluminum cylinder heads, such as the Fel-Pro Copper Ring Head Gasket for small block Chevy engines. When you torque the heads, the aluminum head will not be “scarred” by the combustion seal. A shim style, such as the Fel-Pro Embossed Ring Head Gasket, is another option for use with aluminum heads. When utilizing aluminum cylinder heads on Flathead Ford V8 engines, we recommend using a copper head gasket like this Flathead Big Bore Gasket for 1939 to 1948 engines, or the Best Gasket Flathead Big Bore for 1949 to 1953 engines.

Coatings for Head Gaskets

There is disagreement on whether or not to apply a sealer or coating to head gaskets before installing them. Some men like to use KW Copper Coat or Permatex Copper Spray-A-Gasket as a “copper coat.” Some people used to spray paint their gaskets before installing them. The idea is that it will aid in the sealing of minor defects in the deck or head surfaces. Success can be achieved with or without the use of copper spray; the individual manufacturer will usually mention whether or not to use a sealer with their gaskets.

Tips for Installing a Head Gasket

The head and engine block deck surfaces must be clean, smooth, and flat for head gaskets to seal correctly. Any foreign substance (dirt, carbon, old gasket material, abrasive residue, etc.) on either surface can result in an unsatisfactory seal. Debris can act as a bridge, forming pockets that allow leakage to occur. Any debris can also become embedded in the gasket’s surface. Debris may also cause damage to the surface of the head and/or engine deck, resulting in recurring gasket failure. The diagram below can be used as a reference for small block Chevy engines in general. When disassembling, simply reverse the sequence.

Examining Head Gaskets for Damage

Examine the old gasket for signs of wear and corrosion. This will provide information about previous troubles as well as prospective future problems. A fractured gasket could be an indication of anomalous combustion, such as detonation or pre-ignition. Replacing the gasket without addressing the issue might cause even the best gasket to fail. One of the most typical mistakes made while installing new head gaskets is failing to apply a sealer to the head bolts when necessary. If the head bolts thread into a cooling passage, you must use a thread sealer to prevent coolant from leaking through the bolt passageways.

Place a straightedge longitudinally and widthwise on the head and deck surfaces to inspect for warpage or distortion. You can use a feeler gauge to check for distortion between the deck or head surface and the straightedge. All applications should be no more than.002-inches out-of-flat in width.