Wrenchin’ Wednesday: High-clearance spark plug sockets for tight spaces

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Phillip Thomas

The game of modifying a car really comes down to making a bunch of ill-fitting puzzle pieces cooperate in any way possible. That reality is expressed nowhere more plainly, perhaps, than in exhaust systems and off-the-shelf headers. Many of us have had a set of headers that fit so questionably they make one wonder if the engineering firm of Keller & Charles designed the part. It’s not uncommon to see folks needing to dent and notch headers to clear sockets for the main flange bolts and especially the spark plugs, which are often branching out of the head in a direction aiming straight for a primary tube.

This isn’t just an issue when it comes to melting plug wires, but simply installing the plug can be a bear too; the brittle ceramic insulator that sticks out can easily be broken by twisting a socket onto the socket flats. That tiny, subtle click of a plug breaking can be the last straw, but with today’s Wrenchin’ Wednesday subject, we’ll modify one to make it much better suited for these tight confines.

Phillip Thomas

Real simple, we’re just gonna notch the spark plug we can reach around it at an angle while slipping the socket into place. In this particular case, doing so makes getting the socket onto the number seven spark plug substantially easier, because the socket is no longer rubbing against the header’s primary tube at an angle.

I had originally intended to make this with a nice fillet to the cut, but I realized that none of the drill bits I have are actually hard enough to drill through the hardened steel socket. So, instead, two plunge cuts with a cut-off wheel served to square up the side of the slot before I gently dipped between them to cut horizontally along the bottom. Be sure to grab the rubber grommet that’s inside the socket so that its not destroyed—they help grab the socket (and defy gravity) while extracting the plug.

Phillip Thomas
Phillip Thomas

After checking that the spark plug’s insulator clears the slot easily, I cleaned up the edges with a flap wheel and tested it on the motor.

Phillip Thomas

I can’t even tell you how many times I’ve snapped this guy (and a few others even with the typical torch-and-hammer treatment), so this five-minute modification saves a fair amount of frustration. A few extra bucks, too. On top of that, it can save you time on the dyno. Every tuner has a story about a customer showing up with a mysterious misfire, only to find out that a cracked plug was allowing the spark to escape and short.

This move does reduce the strength of the socket a little, but unless you’re dealing with a boat anchor that was pulled fresh from the sea, no spark plug should be tight enough to split this modified socket to begin with. Well, anyway, that’s a story for another day.

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