Spark plugs that are not properly gapped can lead to a misfiring, inefficient engine. Whether you’ve made serious performance modifications to your vehicle or simply enjoy your daily driver running right, it is important to gap your spark plugs correctly.
What is the proper gap for your spark plugs and vehicle application?
That depends. If this is for your daily driver, your owner’s manual will tell you that information. If you have made modifications or installed power adders, you will need to make adjustments to your spark plug gap.
If you’re not using brand new spark plugs, the first thing you will need to do after removing your spark plugs is inspect and read them. Learn how by reading our post on How to Read Your Spark Plugs.
If you are using new spark plugs, don’t assume the plugs are all gapped the same, or to factory specs right out of the box. The jostling that takes place during shipment can cause the gap between your ground strap and electrode to close.
Whether you need to close the gap or widen it, there are several spark plug tools that can help you set and measure the gap quickly and properly. This installment of Summit Racing Quick Flicks, for example, is a great tool for learning how to properly gap your spark plugs. Check it out:
[…] fluctuating between four or five inches, chances are you have an ignition-related issue. Check your spark plug gap as this condition often indicates too narrow of a gap. Also, check your distributor cap and wires. […]
Nice article, but reading a plug at the race track how can you tell rich/lean or timing issues?
Hi Matt,
Going crazy: Have tried almost everything.
I have taken photos of my new plugs. I have a 2004 Cadillac Northstar with 70K and a random misfire. New coil overs but I think one or two of the injectors are leaking because fuel pressure drops from 30 to 0 in a few hours, but when I disconnected the leads from two of the injectors the engine held the pressure.
My coil overs have 4 prongs but I do not know how to check resistance.
Could I send you a photo of the plugs?