Spark Plug Solid Cap

Spark Plugs Terminals

It's not uncommon to receive new spark plugs or new spark plug wires that seem like they don't fit your vehicle. The part says it will fit your vehicle online, but either the spark plug wire caps are too big, or the spark plug terminals are too small. Most likely, this is because your parts are mismatched with the existing components in your vehicle.

Luckily, this is an easy fix. ALL of our spark plugs have removable ends. Which ensures our spark plugs will fit either style of spark plug wire. Knowing what you are working with will help you get up and running in a breeze. First, let's cover the 3 different types of spark plug terminals.



Solid Terminal

Non-Detachable.

Spark Plug Solid Cap
Solid, non-removable connector terminal. For use with spark plug wires featuring larger snap-over caps. Commonly found in American automobiles.

Removable Terminal Nut

Best of both worlds.

Spark Plug Loose Cap
This is the only style of spark plug we sell. Uses a removable screw-on terminal nut allowing the spark plug to be used with either type of spark plug wires.

Threaded Terminal Stud

Threaded Stud Only.

Spark Plug Stud Cap
For use with spark plug wires featuring smaller snap-over caps which zip onto the terminal threads. Most common in motorcycle and power sports applications. Also known as "European Style".



Spark Plug Wire Caps

A quick peek under the spark plug wire caps reveal what terminal they were designed for. This can vary depending on manufacturer, production year, and even design iterations.

Solid Terminal Cap Spark Plug End

Use with Non-Detachable or Thread On Terminal Cap Spark Plugs

Spark Plug Solid Cap
These plug wire caps are designed for use with Solid Terminals or with the removable terminal nuts on.

Threaded Terminal Cap Spark Plug End

Use with Threaded Terminal Stud Spark Plugs

Spark Plug Stud Cap
These plug wire caps are designed for use with Threaded Terminals or with the removable terminal nuts off.



Check Your Wires/Plug Caps.

If you are ordering both a new set of spark plug wires and spark plugs you can check if they match before installing them. Otherwise, it's a good idea to check what you already have set up in your engine bay. You can easily pull your spark plug wires off in a second without dismantling your engine to check your set up.



This short video shows we are working with threaded spark plug terminals. As these spark plug wire caps are designed for threaded terminals, they are a perfect match! However, these spark plugs came with a removable terminal nut installed on the spark plug when brand new. Our engine builder removed the terminal nuts prior to installation because he saw the wire caps were made for threaded studs.

On the other hand, if we ordered spark plug wires with solid terminal caps, we would need to re-install the removable terminal nut (assuming one still has it) or order brand new spark plugs with removable terminal nuts attached. Removable Terminals Nuts are not sold individually.