How to Replace the Spark Plugs in a Chevy 350

by Christian KillianUpdated November 07, 2017
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Items you will need

  • Wrench set

  • Socket set with spark plug socket

  • Ratchet

  • Dielectric grease

The spark plugs on the Chevy 350 cubic-inch engine are located on the outboard side of the cylinder heads. Depending on the year of the heads, they may be threaded straight into the side or set at about a 35-degree angle. In either case, changing them calls for exactly the same procedure. The Chevy 350 is one of the most popular engines ever produced; spark plugs for it are available from every major manufacturer.

Open the hood of your car or truck and locate the negative battery cable on the battery. Remove the retaining bolt from the battery cable end with a wrench, then remove the negative cable from the battery. Isolate the cable so it cannot make contact with the battery while you are working on the spark plugs and ignition components.

Locate the spark plugs on the outboard sides of the cylinder heads. Each plug will have a spark plug wire running to it. Select a spark plug to start at--it does not matter which one--and grasp the spark plug wire boot, then pull it off the plug. Twisting the boot as you turn it will help to loosen it if it is sticking.

Install a spark plug socket over the spark plug, then attach a 3/8-inch drive ratchet to the socket. Turn the spark plug counterclockwise to loosen it, then remove it from the head. Discard the old spark plug.

Install a new spark plug into the hole in the cylinder head, threading it in by hand to avoid cross threading it. Tighten the spark plug with a spark plug socket and ratchet. Place a small amount of dielectric grease in the boot on the spark plug wire, then push it on to the plug until it snaps into place on the plug.

Move to the next spark plug in the line and repeat the process, never taking more than one spark plug wire loose at a time. When you have completed all the plugs, install the negative battery cable back on the negative terminal of the battery. Tighten the retaining bolt with a wrench until it is snug, then about 1/4 turn more.

Test run the engine after all the plugs have been replaced to verify it is running correctly. Close the hood.


If you are not sure what you need for your engine, ask an associate at any auto parts store.


Never remove more than one spark plug wire at time unless you are sure you know the firing order of the engine. Even one spark plug wire out of place will cause the engine to run very poorly or not at all.

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