Guide: What Is The Spark Plug Socket Size on The S30?

Guide: What Is The Spark Plug Socket Size on The S30?

You might be wondering, "What's the size of the spark plug socket for my S30?" - I get it. Whether you're a new owner or an old one, the answer is important to proper maintenance, and I've found myself digging for my service manual more than once. Or, typing in a quick search into Google, like you probably did!

The Datsun S30 series, a beautiful classic, requires some specific understanding and TLC. Lots of people ignore a really important factor, and that is the right size for the spark plug socket. It's not a detail that you want to get wrong, and there is occasionally some conflicting information out there on this topic.

We're going to talk about all things spark plugs today, from the right size wrench to use, the types of spark plugs that you can try out and that are the right size, and other factors when changing your 240Z, 260Z, or 280Z's spark plugs.

Disclaimer: This article is authored by a member of the Skillard community and reflects their personal views, not necessarily those of Skillard. We welcome your feedback and corrections in the comments to help us continually improve this content.

The Standard Sizes of Spark Plugs

You're looking at either a 14mm or 5/8-inch socket.

Why am I so certain? These are typical spark plug sizes for most vehicles around this time period, and the S30 series stuck to these same specifications.

What else? Well, during that same time period, a 5/8 inch - about 16mm - spark plug socket was the favorite for all sorts of things: cars, bikes, scooters. This wide use of the 5/8 size clearly shows the common manufacturing traditions of the time. But there's no rule book out there that states the specific spark plug socket size for the S30. Can I just go ahead and say it: isn't that a bit odd?

Your mind might be blown, but even through technological leaps and bounds, some manufacturing standards haven't changed one bit. What is the size of spark plug sockets? They've stayed the same for a long time.

Let's focus on this next: terms like 14mm and 5/8 inch. They sound roughly the same in spark plug socket chat, right? But a quick conversion tells us that 14mm is actually 0.551 inches. A 5/8th inch is 0.625 inches.

Spark Plug Sizes

There's a tiny discrepancy, but don't sweat it. Most of the time, a 14mm socket will work for a 5/8 inch spark plug and the other way around, but as for the actual spark plugs, make sure you're getting 14mm plugs.

Some spark plug boxes will even say 14mm on it, like some NGK plugs, but they are actually 21mm, like in this forum thread on Z Club. So make sure to double-check before you accidentally try to install plugs that are the wrong size.

In my opinion, these tiny deviations matter, but changing the spark plug on your S30 series, Datsun will still be a piece of cake! And I can't stress enough how much the right tools will help. We'll talk more about these in a bit.

What Does The Service Manual Say?

The Haynes service manual of the 240Z, 260Z, and 280Z models says to switch out these spark plugs every 10,000 miles.

But factors like how often you hit the road, the state of your engine, and the quality of your spark plugs can switch up this game plan. If you're taking your car to the track every weekend, you're going to want to swap your plugs way more often than that. Bottom line? Listen to what your car is telling you. Notice signs of spark plug wear or dips in engine performance? Time for a check-up!

Tune-Up Page

NGK is the spark plug brand I'd suggest that you start with. Between 1970 and 1974, BPR6ES spark plugs fit 240Z and 260Z models best. But, for 280Z models made from 1977 to 1979, go for the BR6ES11 plug. When you're installing, remember to keep that spark plug gap correct, usually around .030-.035" (.8 to .9mm). Follow the suggested torque of 11-15 lb-ft, too - who wants engine problems, right?

Did you ever think your engine's health - heck, even bigger economic issues - could depend on a simple spark plug? Well, for these of you with a Datsun packing an L28 engine, choosing the right plug between the BPR6ES and BPR5ES-11 could make all the difference.

Some people like to use thread lube or anti-seize on the spark plug threads to stop 'em getting stuck. Though, you should remember to check and make sure they don't already have lubrication from the factory, as most spark plugs do and adding additional lubrication can actually be detrimental

Lost in the specifics? Are you confused about the details? Your Datsun's service manual has your back. Even better? Chat with other Datsun enthusiasts. There are heaps of helpful resources, and people are eager to share advice on HybridZ,  Zclub, and other similar forums.

Which Spark Plugs Work Best?

Datsun S30 series cars - like the 240Z, 260Z, and 280Z models - drive at their peak when fitted with the right spark plugs (like the NGK BP6ES I mentioned earlier).

People who are into cars give these spark plugs two thumbs up thanks to their solid dependability. These plugs are a winning match for the L24, L26, and L28 engines because they last a long time; they function well under a variety of temperatures and pass electric current super well.

L28 Engine by RVAE34

Image source: Photo by RVAE34 on Flickr / CC BY-NC-ND 2.0


How do you squeeze the best performance from these engines? The answer is: find the right spark plugs! The correct spark plugs don't just crank up the power; they also shield the engine from damage. The NGK BP6ES nails this balance, no matter the road conditions.

When popping in this spark plug, it's really important to pay attention to the little things. Again, remember to apply thread lube or anti-seize on the threads. Trust me; it's important. I insist on sticking to the factory-recommended gap of .030-.035" (.8 to .9mm); it's a must-do.

What about the torque specification for the spark plug? You'll find that in the factory service manual; it's set at 11-15 lb-ft. Seems trivial, right? Well, think again - it plays a big part in the whole engine's performance. You can get a torque wrench specifically designed for spark plugs.

What Tools Come in Useful for Changing Spark Plugs?

The right tools make this job a lot easier. The worst thing you can do is try to take your spark plugs out with the wrong size wrench or start torquing on or off your spark plugs with the wrong tool. You won't be too happy with yourself if you end up causing thousands in engine damage over a quick run to an automotive store to get the right tools.

Spark Socket

The spark plug socket is mandatory, but the others are nice to have:

  • So, first, you'll need to grab the right tools to replace the S30's spark plug.
  • High on my recommendation list is a spark plug socket with a rubber boot or magnet; it safely handles plug installation and removal. Also, it helps the delicate porcelain insulator last longer. And, the 6-point end helps cut down on spark plug deterioration.
  • Next, you'll need a ratchet wrench to work the spark plug socket. But which kind - short, standard, long-handled, flex-head? That's up to you, depending on what you need.
  • What if you run across a spark plug tucked away in a strange spot? That's when a swivel spark plug socket turns into a must-have. Its bendy joint lets it maneuver around obstacles and reach deep-set plugs, a big time-saver!
  • Of course, you can't forget about the gap between the spark plug's side and central electrodes. Adjusting this gap needs to be spot on, so a spark plug gap gauge is really important. It measures and sets the gap to line up with what the manufacturer recommends.
  • Surprisingly useful is the Spark Plug Wire Pliers, especially for snagging these hard-to-reach spark plug wires. Their straight or offset designs make the job a whole lot easier - and help maintain the wire boot's integrity.
  • And what about boot removal? That's where needle-nose spark plug pliers shine. Their serrated jaws keep plugs from getting damaged - a neat bonus.
  • Avoid over-tightening a spark plug with the Tekton Click Torque Wrench, a medium-duty torque wrench. This tool will make sure the plug is tightened just right, according to model specs.
  • In some cases, you won't get by without offset boot pliers. Imagine your spark plug wires are buried deep in the engine; the 45-degree angle design of this tool makes the removal process very easy!

Last but not least, spending money on the right toolset can make replacing your Datsun S30's spark plug so much easier, and you know what? You'll get better at it, too!

How Difficult Is It to Change the Spark Plugs on The S30?

If you have some decent mechanical skills, swapping out spark plugs on an S30 series Datsun is totally doable. It's not rocket science, but you'll need the right tools and a few important pieces of knowledge.

What tools do you need? We covered a lot in the previous section, but a 21mm or 13/16in deep spark plug socket is the most important. You'll use it for pulling out old plugs and putting in the new ones. It's my opinion that NGK BP6ES spark plugs make the S30 Datsun really hum, although you won't go wrong with other brands either.

Note - always keep an eye on the gap sizes. NGK BP6ES spark plugs come from the factory gapped at 0.031in (0.8mm). That's usually fine, but double-checking never hurt anyone. Scoping the gap measurements is absolutely important for the 240Z and 260Z models, which need a gap between 0.8mm - 0.9mm (0.031-0.035in). For the 280Z model, though, they want a slightly larger gap of 1.0 mm - 1.1 mm (0.039-0.043in).

Gap Size

Before you dig in, make sure the area around the spark plug isn't dirty. After all, who wants gunk in their combustion chamber, right? Use that special spark plug socket to pull out the old plugs gently. Looking at the old plugs can give you a decent idea of how your engine's doing.

Swapping in new plugs? Remember to put a little smear of anti-seize on the threads so they don't get stuck, but only if there isn't any lubrication on them yet. Go gently with the threading; hand tightening first will make sure you won't mess up the threads. Once that's done, grab your torque wrench and apply torque in the 11-15 ft. lbs range.

Let's be clear: replacing spark plugs is a job for finesse, not muscle. Watch your gap dimensions, don't overtighten, and you'll get the job done right.

Regular spark plug replacements (think every 10,000 miles or so, sooner if you're racing) are important to keeping the S30 Datsun in tip-top shape and maximizing gas mileage. By sticking to a solid maintenance schedule, you can give these classic beauties a whole lot of extra road time!

Keep Your S30 Looking and Running Great

Research is the root of my growing appreciation for the Datsun S30 series. But it's in the meaningful bond of engineering and design that the history and inventive technique to upkeep the Datsun S30 series shine. Really important details - like just the right spark plug size and regular preservation - become important; they're important in improving and overseeing the performance of these vintage vehicles.

As time goes by, these old-school cars might need other parts; it's not exclusively about the right spark plugs or socket size. That's where Skillard comes in (that's us!)

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The quality of your car mirrors its parts. Give your antique Datsun - and, in fact, your life - what it deserves, and improve the performance and styling of your car! Check out our catalog, and pick out the perfect parts to breathe new life into your Datsun project. And if you have any questions, get in touch with us!

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