Can You Replace Just One Cylinder Head On An Engine?

When replacing cylinder heads on an engine, like a V-twin, V6, V8, or a horizontally opposed variety, it's possible to get by with replacing just one head. Of course, if your engine only has one cylinder head, like a single cylinder, parallel twin, inline-four, or -six, this question doesn't apply.

If you don't know the difference between an engine block and a cylinder head, that's alright. However, you should know that the cylinder heads bolt to the engine block, separated by a head gasket that seals the gap between the two components.

When a cylinder head fails, it's often due to a broken or bent valvetrain component that causes a valve to contact the piston in the engine block. That scenario typically causes damage to more than the cylinder head. Other times, a cylinder head may crack, or the engine's head gasket could blow out, damaging the head's mating surface.

If the head damage is confined to one cylinder bank, it is tempting to only repair that side in an attempt to save money. While it is better to replace, or repair, both cylinder heads at the same time if possible, you can replace just one, but you should be aware of the potential risks.

Similar to the risks of replacing just one tire on an AWD car, replacing a single cylinder head can lead to problems later. For starters, bolting a fresh cylinder head onto a worn engine could cause the side with the new head to have more compression than the other. If the replacement head is of a different casting design, it could alter the airflow through the engine and affect its performance.

While replacing just one cylinder head can save money upfront, it may end up costing more in the long run. On a V6 or V8 engine, both heads share much of the teardown, so if the other one fails soon after, you'll have to pay for that labor twice. 

Ultimately, a complete rebuild of a high mileage engine is best, but if you're looking at replacing one cylinder head as a quick fix, there are some things to consider. As mentioned, an engine that's suffered valvetrain components rattling around inside the cylinder will require more than a cylinder head replacement. In addition, if engine overheating caused head failure, there could be other issues behind the problem.