Why are spark plug tools 3/8 drive?

[qqzj]

Most Denso or NGK plugs use about 13-15 ft pounds torque. I have seen good quality 1/4 ratchet fails at about 70 ft lbs. So spark plug tools are right in the alley of 1/4 tools. So I am pretty puzzled why most spark plug specific tools use 3/8 drive? Given the increasingly crowded engine bay 1/4 makes a lot more sense, doesn't it?

One possible explanation is that 1/4 torque wrench often stops at 15 ft lbs or so. Then it is natural to ask why not make a 1/4 torque wrench going up to 30 ft lbs? As of now, using chunky 3/8 tools for spark plugs seems pretty dumb. Any opinions?

 

[strutaeng]

Umm...

You actually torque spark plugs? I've never done that myself (which obviously doesn't make it right). I just kinda snug them up tight.

I guess it depends on the vehicle you are working on. Most of my vehicle are full size gmt800 trucks. Plenty of room to put a nice 3/8 ratchet for spark plugs. Maybe one plug requires a swivel to clear the steering wheel shaft.

I do own a 3.6 Pentastar transversely mounted engine configuration. I haven't done spark plugs on it, but do know transverse engines are a pain compared to longitudinal, so I can understand your question.

 

[finn]

I take it you don’t work on many high mileage engines that spent their life in the salt belt.

 

[engineer2]

I suspect many early ratchets were 3/8 or 1/2 drive. Any way to see on old patents?
Torquing spark plugs became more important with aluminum cylinder heads, in my opinion.
We never used a torque wrench on iron heads.
Here in the rust belt, you would break a 1/4 drive.

 

[msharley]

I take it you don’t work on many high mileage engines that spent their life in the salt belt.

 

[qqzj]

I take it you don’t work on many high mileage engines that spent their life in the salt belt.

That just means 3/8 is necessary in certain scenarios. But it does not mean 1/4 is not the theoretically correct tool. In fact in California, and many other places, 1/4 should be the practically correct tool as well

 

[66HertzClone]

I can remember struggling to loosen those 18mm thread plugs, can't imagine doing that with 1/4 drive tools.

 

[Kuma601]

The 1/4" spec does fall in that range. The shorter 1/4" drive handles to break them free I would not enjoy, the 3/8" ratchet lengths work fine for me.

 

[T45]

Depends on application You can get 1/4 drive, 14mm sparkplug sockets for motorcycles. Some of the earlier issues don't typically apply to motorcycles, the access issues are less, and they are much better protected vs corrosion, many are high-performance motos are regular getting wrenched on, etc.

https://www.amazon.com/dp/B07HHKJXF1/?tag=atomicindus08-20

 

[Hohn]

I take it you don’t work on many high mileage engines that spent their life in the salt belt.

Yeah, I was actually thinking as I read the OP: "great point, why not make them 1/2" drive?"

 

[purplezr2]

Do you work on cars much?

Usually a short 3/8 is hard to remove sparkplugs.

 

[MattGarage]

I've collected several sparkplug sockets over the years. Even between 1/2 and 3/8. Torque is probably the reason though. Nothing like overtorquing a spark plug. A hard to remove spark plug is a spark plug installed incorrectly.

 

[ctandc72]

I've collected several sparkplug sockets over the years. Even between 1/2 and 3/8. Torque is probably the reason though. Nothing like overtorquing a spark plug. A hard to remove spark plug is a spark plug installed incorrectly.

Well some Ford 4.6 2V engines came with a not-so-rare automatically ejecting spark plug option. So there is that.

 

[MattGarage]

Well some Ford 4.6 2V engines came with a not-so-rare automatically ejecting spark plug option. So there is that.

The 460 came with that feature! And exhaust manifold ejecting too.

The chevy 454 to a lesser degree. First hand experience on both.

 

[finn]

That just means 3/8 is necessary in certain scenarios. But it does not mean 1/4 is not the theoretically correct tool. In fact in California, and many other places, 1/4 should be the practically correct tool as well

Not really. Cars are pretty much fungible as far as markets go. A car may live in PA along Lake Erie for ten years, then be driven to San Diego for the rest of its life, or vice versa.. You don’t redesign common parts for the five people living in California that think a 1/4” plug socket would be cool. Especially since the other 20 million don’t GAF what size the drive is, as long as it works.

The other reason is that 3/8” and 1/2” drive ratchets were the most common sizes available when spark plug sockets were developed. 13/16” hex plugs were common from the twenties until the 70s, when 5/8” hex plugs became common.

you can always use a 1/4” ratchet with an adapter if it’s important to you.

 

[dchawk81]

That just means 3/8 is necessary in certain scenarios. But it does not mean 1/4 is not the theoretically correct tool. In fact in California, and many other places, 1/4 should be the practically correct tool as well

Tightening ain't loosening, bro. There's a thing called leverage that you sometimes need.

Unless you want to buy a special 1/4 drive with the body size of a 3/8 instead of using a 3/8 with the body size of a 3/8. If so, do your thing.

 

[whateg01]

Yeah, I was actually thinking as I read the OP: "great point, why not make them 1/2" drive?"

I have spark plug sockets in 1/2" drive also.

 

[whateg01]

I've collected several sparkplug sockets over the years. Even between 1/2 and 3/8. Torque is probably the reason though. Nothing like overtorquing a spark plug. A hard to remove spark plug is a spark plug installed incorrectly.

Unless it's a Ford mod with the spark plugs that extend past the threads far enough to allow carbon to build up and not want to come out without pulling the aluminum threads with it.

 

[bcradio]

Socket size is why

 

[finn]

I've collected several sparkplug sockets over the years. Even between 1/2 and 3/8. Torque is probably the reason though. Nothing like overtorquing a spark plug. A hard to remove spark plug is a spark plug installed incorrectly.

You’ve never pulled plugs from an 88 Chevy plow truck, either.

You should probably get out of mom’s basement more often.

Do you know how thin the outer shell is on a Bosch iridium plug? I didn’t either until I had to peal one out of the head on a 350 SBC With a pair of needle nose pliers.

 

[finn]

I have spark plug sockets in 1/2" drive also.

That’s all I had until I was almost thirty.

 

[ctandc72]

Unless it's a Ford mod with the spark plugs that extend past the threads far enough to allow carbon to build up and not want to come out without pulling the aluminum threads with it.

Buddy of mine was a Ford Dealer tech during those lovely early 4.6 2v years. He'd always say - if it don't come loose with a hard pull on the ratchet, it doesn't need plugs.

 

[mikedodge]

The last thing that I've ever thought of with spark plugs is using a 1/4 ratchet with them. Even in tight spaces the problem isn't getting a ratchet in there it's turning it. 3/8 is the ideal ratchet size for spark plugs.

 

[Firebrick43]

That just means 3/8 is necessary in certain scenarios. But it does not mean 1/4 is not the theoretically correct tool. In fact in California, and many other places, 1/4 should be the practically correct tool as well

Ahh, those Californians that believe that they are the center of the universe.

 

[whateg01]

Buddy of mine was a Ford Dealer tech during those lovely early 4.6 2v years. He'd always say - if it don't come loose with a hard pull on the ratchet, it doesn't need plugs.

I'm lucky. I have the self ejecting version. So far I've only had to fix 2 of them.

 

[lolaetype]

Any opinions?

I'd guess back in the day the average occasional home mechanic most likely only had a 3/8" drive socket set since that would cover most of their socket/ratchet needs. Also, my 1/4" drive Craftsman socket set which dates from the 1960's only goes up to a 1/2" socket. To me that's a clear indication the manufacturer didn't expect that size drive to be used on anything larger.

 

[nadogail]

3/8" drive is big enough to work and has many years behind it, 1/4" drive may be big enough to work, but I personally have no confidence in using it for anything; 3/8 has worked well for me for years.

 

[dcg9381]

Umm...

You actually torque spark plugs? I've never done that myself (which obviously doesn't make it right). I just kinda snug them up tight.

I do that also. Unless I'm working on a Ford V10. I that case, I break out the torque wrench.

Ford Triton Spark Plug Issues Explained - Blowout & Broken Plugs

What Triton engines have spark plug problems? See our breakdown of which engines suffer from plug blowout and broken spark plugs.

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[yatg]

glue this in your spark plug socket and be happy

https://www.amazon.com/dp/B08J1KDS2B/?tag=atomicindus08-20

 

[msharley]

Well some Ford 4.6 2V engines came with a not-so-rare automatically ejecting spark plug option. So there is that.

Been there. Done that.

Have two friends with the 5.4.....that have done all 8 of them!

Another brilliant effort from the "design team"....

 

[Garcky]

I almost never use my 1/4" drive stuff. I mean, I do, but not on cars, really. My go-to stuff is all 3/8" drive. 1/4" drive is for 7/16 and below. 12mm and below, these days.

Spark plugs. They corrode in place. 1/4" drive won't work. You need a little more torque than you can get from some 6" long ratchet.

 

[MattGarage]

You’ve never pulled plugs from an 88 Chevy plow truck, either.

You should probably get out of mom’s basement more often.

Do you know how thin the outer shell is on a Bosch iridium plug? I didn’t either until I had to peal one out of the head on a 350 SBC With a pair of needle nose pliers.

88 chevy plow truck? What kind of engine is that? They only made so many.

Sounds like you got up on the wrong side of the bed. Kinda hard to do in that double! Don't worry - you won't have all off days on those hormone blockers you're on, Caitlyn

 

[Chrome Vanadium Cody]

I went through this with my moped, 1/4” works for everything else on it and I didn’t want to bring an extra drive tool, so I got the kind with a hole you can stick a screwdriver through and use that. Nature of the beast is I will always foul the **** out out of the sparkplug before it has any chance of rattling loose OR corroding.

 

[cgrutt]

I like to use 1/4 drive tools but usually for 8mm or 10mm rarely above 1/2". Honestly wouldn't want to remove a sparkplug with anything other than 3/8". Just comes down to preference and what you're accustomed to I suppose.

 

[slowtwitch73]

Put an adapter on a 1/4 and have at it.... you'll be back to 3/8 after a while.

 

[pelletman]

Have you ever actually removed a spark plug?! I have spark plug sockets that are 1/2" drive

 

[T45]

Have you ever actually removed a spark plug?! I have spark plug sockets that are 1/2" drive

Clearly not with a 1/4 drive socket, because even a deep regular doesn't fit, not enough bolt clearance. So even if you have a 14mm (9/16) application, you need 3/8 drive version of the 14mm (9/16) Deep socket to get the 75mm (3in) vs 50mm (2in) OAL.

 

[MarcSeattle]

Thanks, I needed an avatar pic!

 

[scooby074]

Why 3/8? Because thats the way it is. Thats why !!

 

[bbrins]

You're probably not going to be removing many factory installed plugs with a 1/4 drive ratchet before you wind up back using 3/8. I don't know what they tighten plugs up with at the factory, but they sure ain't using 13-15 ft/lb as the spec. I've had a few times where I felt like 3/8 drive wasn't enough.