Spark Plugs, Beam Torque Wrench?

use a torque wrench

Wow. The problem I have with the advice given in the thread has to do with the EXTREAM difference in experience level of the readers.

Some of us have been doing this for years maybe even for a living. However, some of the threads are stated by ppl asking questions such as "where are the vacuum hoses?".

The torque wrench takes the guess work out of it. Putting the newbie on an even playing field with the pro.

Some of these same posters would spend 5x on special oil for minimal perceived benefit and won't take the time to torque their spark plugs? IMO, doesn't make sense.

The plugs back out because 11 lb-ft is not much torque. There is so little difference between too little and too much it's easy to get it wrong.

The 5 minutes you saved by not using a torque wrench will come in handy installing inserts when the spark plugs blow out.

40oz said:

Good god. Using a torque wrench on plugs or lugnuts just sets you up for a failure. It's just a number, nothing more. You can still screw it up by relying on a tool to think for you.

Plugs see very little tendency to back out unless they aren't even tight to begin with. As has been said, finger tight then snugged with a rachet. And snug does not mean "that bitch ain't EVAR coming out!" It means snug. You could still turn it in farther easily by leaning on it, but there is no need. You aren't holding a head on or preventing your wheels from flying off, you are merely threading something in so it seats and seals.

And even if you are fastening on your head or wheels, you still don't need a breaker bar or gorilla strength. If you tend to strip or break bolts because you mindlessly apply all your force to each and every fastener, torque wrenches were made for you. The rest of us reasonable souls get by using common sense and basic arm strength for fastening. Body weight is only used for removal of stubborn/rusted pats, *not* attachment.

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I hope you torque heads in proper sequence and torque the bolts properly


Ok I understand not wanting to buy a torque wrench for the plugs.. and I have never used a torque wrench on wheels ( I have torque sticks for my impact gun for that) If you torque a wheel down uneven you may warp your brake rotors over time not a big deal.. but it's worth it to take the time to torque a head down right.. Improper torqued TTY bolts is a setup for failure



The reason why I recommended using a torque wrench on the plugs is because over torquing the plugs on these motors damages the threads, and we don't have many threads to begin with.

Do I use a torque wrench on all of them i do... NO but I have been doing this for a long time and have enough feel that I can do it by hand and be really close..

Just like anything else you get a feel for it over time.. For example I have setup enough 8.8 pinions that I can set rotational torque by feel then check it and find it's spot on... For a guy doing his first one I would never suggest doing that.. I would tell them to check rotational torque properly

That write up I did on it back in the day was intended for a hobbyist with little experience working on cars.. Until that person gets a feel by hand he or she should use a torque wrench.


Not using a torque wrench does not make you a better mechanic it makes you a mechanic with a lot of come backs.. I have had to fix quite a few chattering clutches that were done by the goodentight crowd and quite a few rear ends by the " you don't need to measure anything unless you replace the case" crowd.. even had to redo heads that were done by somebody who did not torque them down right.

wmburns said:

Wow. The problem I have with the advice given in the thread has to do with the EXTREAM difference in experience level of the readers.

Some of us have been doing this for years maybe even for a living. However, some of the threads are stated by ppl asking questions such as "where are the vacuum hoses?".

The torque wrench takes the guess work out of it. Putting the newbie on an even playing field with the pro.

Some of these same posters would spend 5x on special oil for minimal perceived benefit and won't take the time to torque their spark plugs? IMO, doesn't make sense.

The plugs back out because 11 lb-ft is not much torque. There is so little difference between too little and too much it's easy to get it wrong.

The 5 minutes you saved by not using a torque wrench will come in handy installing inserts when the spark plugs blow out.

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EXCELLENT post wmburns I guess some folks choose ego over doing it correctly. Perhaps that shows why some people have the blowout issues, and others who torque it, dont have to mess with inserts and new heads.

Where did you get your inch lb torque wrench and how much did you pay for it?
Don't tell me you are using a ft lb torque wrench...there is no way it is accurate enough for your specs.

ppl make it out like the threads are made of clay or something. we may be limited in threads but sheesh they're not made out of play do'.
You dont need this torque wrench nonsense. no one that does this for a living uses torque wrenches on plugs. Crap, I use to work at a German car dealer..we torqued nearly frikin every damn bolt removed except plugs. my redneck Ford doesnt need all that to run top notch like these POS over priced german cars.

Jbauer said:

ppl make it out like the threads are made of clay or something. we may be limited in threads but sheesh they're not made out of play do'.

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The problem is that the 2V 4.6L engine has a proven track record of spark plug blow-outs if the plugs are not properly torqued. It's really that simple. Without a torque wrench, you're guessing and that can lead to an expensive and inconvenient repair later, all in the name of saving 20-seconds a plug. Given how easy the things are to access, it makes no sense to take short cuts like this.

You dont need this torque wrench nonsense. no one that does this for a living uses torque wrenches on plugs.

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In my experience, people that "do this for a living" but who can't be bothered to use the right tool for the job have given the car-repair business a bad name. Wouldn't surprise me if the saying that goes "If you want it done right, you have to do it yourself" became popular because the attitude that "goodentite" is "goodenuff" which prevails in the auto repair industry.

The latest event to grace my household involved my wife's Mazda6. She complained the car was "making noise in the front." We took it for a quick drive and I suggested we checked the passenger side front wheel bearing. When I got it off the ground, I immediately noticed every lugnut on the wheel was loose and the wheel was moving on the hub 1/16" by hand. I pulled out the torque wrench (yes, a torque wrench) and checked all the lugs on the car: of course every lug on that wheel was loose but there was a remarkable difference in the tightness of every other lug on the car. Some were fine but many were in various states of needing more than 1/4-turn to reach the proper torque. The car had just been in for service at the local dealership and they'd "serviced" the brakes. In other words, the very people that do this for a living put my wife's life at increased risk because someone just couldn't take the time to do the job right.

While a plug blowing out may not carry the risk of a loose road wheel, I still would not like my wife -- or myself for that matter -- to be driving on the highway and finding herself on the shoulder with a dead car, semis whooshing by at 75MPH -- because someone who fixes cars for a "living" couldn't be bothered to walk over to their toolbox and get the right tool.

Crap, I use to work at a German car dealer..we torqued nearly frikin every damn bolt removed except plugs. my redneck Ford doesnt need all that to run top notch like these POS over priced german cars.

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These particular "redneck" Fords have proven themselves to be very sensitive to spark plug torque. Anyone that blithely refuses to learn from the experiences of others with regard to torquing plugs on these cars deserves to find themselves stranded somewhere facing a multi-hundred dollar repair bill. Hopefully their refusal to learn from those incidents doesn't cause someone else the same inconvenience and out of pocket expense.

twogts4us said:

Where did you get your inch lb torque wrench and how much did you pay for it?
Don't tell me you are using a ft lb torque wrench...there is no way it is accurate enough for your specs.

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I use a Craftsman Digitork Torque Wrench, 5-80 ft. lbs., 3/8 in. Drive.

http://www.sears.com/shc/s/p_10153_12605_00944596000P?keyword=craftsman+torque+wrench

Mine is older than above. It has a range of 5-70 foot pounds. Therefore, 11 foot pounds (15 Nm) is within it's range. I have it had for 20+ years. Over the life of the tool, it really isn't expensive.

With regards to the point made by twogts4us and accuracy, I would put it up against any human torque wrench out there.

Personally, I think the fancy “electronic digital” torque wrenches are not worth the added expense for the home hobbyist. Especially if the $$ keeps it from being used.

For the truly budget conscious, there is the old stand-by beam style. I would trust that almost everyone can afford a $30 tool.

I also put anti-seize on the top threads near the seat. This act as a lubricant making more consistent torque readings. Not to mention, makes the next removal of the plugs easier.

Those of you out there that have a 2005+ 3 valve engine, if you don’t use a torque wrench you are in for an entirely different experience. In fact, a torque wrench is needed to REMOVE the spark plugs (do not exceed 35 foot pounds).

the issue I have with torque wrenches? It's a big ass breaker bar. You have no idea of the stress you're putting on things when you use it. Oh sure, you have a number you are pretty sure this bolt needs. But what happens when you apply foot-pounds and the spec calls for inch-pounds? Or you read 125 ft-lbs. but that is for another fastener and the one you are on needs 65 ft-lbs? You are two feet removed at least from feeling the stress on the part, so breaking bolts is easy. You'd know to stop if you relied on feel, but since the torque wrench hasn't clicked, you keep leaning on it until it snaps.

And at the end of the day, you don't know how tight it is, you only know your torque wrench clicked or slipped. You were at the end of a breaker bar, so your concept of how tight it is might as well come from Mars. I'd rather have a tactile feeling of how much pressure I put on things. At least then I know it is tight or loose or whatever. I am not a monkey, so I can tighten things just past snug, or lean on it, or just bring it to the seat. On the end of a breaker bar, I won't know if it is seated until the bolt snaps.

Would you feel better if your engine ejected a plug but you "torqued it to spec"? Or would tightening it by hand so it is snug using a regular ratchet give you peace of mind? I know where I stand. I'm not going to rely on a torque wrench to tell me my lug nuts are tight. You mileage may vary. If my wheel falls off, I'm not going to make it better by saying "but I used a torque wrench!?!"

Torque numbers are just numbers. Kind of like tightening sequence. If you can't look at a part and guess the sequence, you *need* the instructions. But it should be obvious. Engineers aren't geniuses, they just study and break parts and try again. Sometimes they only write instructions after someone breaks parts. The average person can grasp what is required with a bit of thought and a modicum of experience. Tightening sequences and torque specs are written for the idiot quotient. An idiot is someone who can't figure out how to tighten a wheel, or reads the instructions on how to tighten a wheel and doesn't figure out that a head should probably be tightened the same way.

Most people aren't idiots. Just don't tighten everything to German "gooden'tight" specs irrespective of the part. That's just stupid. Plugs only need to be snug. Wheel lugs need to be tight, but only arm tight, not body-weight tight. And not gorilla-arm tight. Check and re-tighten lugs after driving a mile or so. Check plugs the next time you change your oil just to be smart, but use your fingers. If your fingers can move them, get out the wrench, but not before. And grab it around the socket, not at the end. You DO NOT want to break a plug off in your head, or strip the head.

Seriously, you should be able to interpret torque specs into "arm calibration." I understand if you work at shop why you rely on the tool. But even in shops there are gorillas who break bolts, strip drain plugs, and generally make a mess even with torque wrenches. They're the guys telling you that you have stripped wheel studs or need to replace head bolts after an oil change. Obviously torque wrenches don't solve the world's problems :/

All that said, perhaps I'm not typical. I'm not the kind of person to say I have skills you can't learn. But what do I know? Some people have perfect pitch. Is it possible for a person to have perfect torque? (I'm not saying I do. I'm just saying perhaps I'm naive and know things I don't even know I know)

And for the record, Honda's S2000 is known to eject the #4 plug. Same issue, but Honda blames the customer rather than re-spec the part or fix the problem. Think of that before you blast Ford. At least they suggest a different plug.

I'm not disputing the posts before me. They provide good info, and are coming from intelligent people with real world experience. I'm just saying that torque wrenches are not a panacea. They provide "scientific" torque used correctly. But the kicker is the "used correctly" thing. Often you are better off not using one than risking using one incorrectly in your driveway. And truth be told, even "torque to yield" head bolts can be tightened properly without one.

40oz said:

the issue I have with torque wrenches? It's a big ass breaker bar. You have no idea of the stress you're putting on things when you use it.

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On the contrary, you know exactly how much strain you're putting on it. Stretching a bolt a known amount is the reason why torque wrenches were invented.

Oh sure, you have a number you are pretty sure this bolt needs. But what happens when you apply foot-pounds and the spec calls for inch-pounds? Or you read 125 ft-lbs. but that is for another fastener and the one you are on needs 65 ft-lbs?

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Any tool can be mis- or improperly used, sort of like the goodntite crowd using 400ftlb impact guns to speed on lug nuts.

And at the end of the day, you don't know how tight it is...

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On the contrary, you know exactly how tight the fastener is.

I'd rather have a tactile feeling of how much pressure I put on things.

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I'd rather have a calibrated tool telling me that and using good judgement to tell if something is wrong (i.e. the wrench clicked early or is late...)

At least then I know it is tight or loose or whatever. I am not a monkey, so I can tighten things just past snug, or lean on it, or just bring it to the seat. On the end of a breaker bar, I won't know if it is seated until the bolt snaps.

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I said in one of my previous posts that I wouldn't use a 1/2" "breaker-bar"-long torque wrench to tighten low-torque fasteners. For instance, a 3/8" torque wrench like this:



would be suitable for such fasteners as plugs. Or for really low-torque fasteners like camshaft cap bolts (89inlb or 7.4 ft-lb) I'd probably look into something like this:



which can also be used to measure stuff like pinion bearing preload.

If you think the only torque wrenches are the 250ftlb "breaker bar" variety you should check out, say, Snap On's collection of torque wrenches.

Would you feel better if your engine ejected a plug but you "torqued it to spec"? Or would tightening it by hand so it is snug using a regular ratchet give you peace of mind? I know where I stand. I'm not going to rely on a torque wrench to tell me my lug nuts are tight. You mileage may vary. If my wheel falls off, I'm not going to make it better by saying "but I used a torque wrench!?!"

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First, the plug is less likely to eject and the wheel less likely to separate if the fasteners are properly torqued to factory specs.

Second, do you trust everyone else's judgment as to what's "goodntite"? Is everyone's touch as deft as yours? Any variation? Is a 250# strong-man going to feel the same tactile feedback as a 98# weakling wielding a ratchet? Would you feel comfortable letting your wife drive a car that just had major suspension or brake work done by someone else who did the fasteners up "just so"?

Torque numbers are just numbers. Kind of like tightening sequence. If you can't look at a part and guess the sequence, you *need* the instructions. But it should be obvious. Engineers aren't geniuses, they just study and break parts and try again.

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Torque is far more than simply a number and with respect to stress, strain, metallurgy, loading and every other engineering facet of automotive design, compared to most everyone engineers are geniuses. Granted, sometimes they screw up such as not providing sufficient threads in the head for a spark plug. This simply makes the accurate torquing of the plugs that much more critical...

Bolt torques aren't just guessed at. They don't follow the "tighten it till it starts getting loose then back it off a 1/4-turn" credo of the goodntite crowd. I'm not going to bother explaining how different grades of fastener material, thread pitch, fastener diameter and so on all go into determining what the correct torque is to achieve a desired stretch or clamping or preload but I will say these guys aren't guessing.

Most people aren't idiots. Just don't tighten everything to German "gooden'tight" specs irrespective of the part. That's just stupid. Plugs only need to be snug. Wheel lugs need to be tight, but only arm tight, not body-weight tight. And not gorilla-arm tight.

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But a 250# NHL defense man has a different definition of "arm tight" than your 98# accountant does.

^ Amen to everything trinity_gt just said. Engineers *are* in fact geniuses(I know because I'm trying to become one), and there is a lot of math and physics principles that go into these pieces. They don't just make something and see if it breaks, the whole point of an engineer is to apply mathematics and physics to solve a problem, it isn't a trial and error strategy. If they say the torque needs to be X amount, they aren't ball-parking it, and they will do destructive testing to prove their math is correct. And I don't necessarily think the engineers even messed up with the plug threads in the mod motors, there is simply less tolerance for idiots to do it by "feel". If you use the correct torque values *from the very beginning* I'm sure you will never have a problem.

wmburns said:

I use a Craftsman Digitork Torque Wrench, 5-80 ft. lbs., 3/8 in. Drive.

For the truly budget conscious, there is the old stand-by beam style. I would trust that almost everyone can afford a $30 tool.

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Yeah, but your wrench is $110.00...

wmburns said:

Those of you out there that have a 2005+ 3 valve engine, if you don’t use a torque wrench you are in for an entirely different experience. In fact, a torque wrench is needed to REMOVE the spark plugs (do not exceed 35 foot pounds).

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Well how can that be? And what do you do if 35 ft lbs doesn't remove the plugs?

40oz said:

the issue I have with torque wrenches...

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EXCELLENT POST!

trinity_gt said:

If you think the only torque wrenches are the 250ftlb "breaker bar" variety you should check out, say, Snap On's collection of torque wrenches.

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Yeah, the cheapest torque wrench at Snap On is $170.00. The CHEAPEST!

DIERDORF_237 said:

^ Amen to everything trinity_gt just said. Engineers *are* in fact geniuses(I know because I'm trying to become one)

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What? You're already a genius? Or do you mean because you are going for your engineering degree that you will soon be considered a genius?

DIERDORF_237 said:

And I don't necessarily think the engineers even messed up with the plug threads in the mod motors, there is simply less tolerance for idiots to do it by "feel". If you use the correct torque values *from the very beginning* I'm sure you will never have a problem.

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Yes they did, Mr. Idiot Genius - they later fixed the issue.

It's funny how the people complaining about the cost of a tool would willingly cough up way more than that to repair a head when a plug blows out.

twogts4us said:

What? You're already a genius? Or do you mean because you are going for your engineering degree that you will soon be considered a genius?

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When did I say I was a genius? That would imply that I already have my degree, but I specifically used the word TRYING. I meant since I'm in school I'm realizing just how difficult engineering is, and have a ton of respect for engineers. Would I like to be a genius one day? Sure. Who wouldn't?

If the guys that brought the part into reality wouldn't trust their own "feel", why should I? I'll go the fail-proof route and not have to heli-coil my plug holes. The engineers have taken the guess work out of it and provided you with torque values. They've done the work so you don't have to.

twogts4us said:

Yes they did, Mr. Idiot Genius - they later fixed the issue.

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They probably fixed the issue because nobody could grasp the concept that a torque wrench might actually be necessary, everybody was so used to ball-parking it. They design something to an exacting standard and everyone throws a hissy-fit so they have to dumb it down because people are too lazy to do the job right.

Do I know that that is what happened? No, but it sure seems likely.

twogts4us said:

Well how can that be? And what do you do if 35 ft lbs doesn't remove the plugs?

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If that were the case, it would be because either someone didn't torque them properly in the first place(35 ft. lbs. is way too tight, must have been an idiot doing it by their precisely calibrated "feel"), or more likely the dissimilar metals caused corrosion between the steel threads of the plugs and the aluminum threads of the head because they didn't use an anti-seize compound.

If the threads are corroded together and you use more than 35 ft. lbs. you will likely rip all the aluminum threads out of the head. However there are options. I'd soak them in penetrating oil before trying again, and if that doesn't work maybe heat the area.

Either way the only reason they would require more than 35 ft. lbs. to loosen would be because the job wasn't originally done right because someone thought they were smarter than the engineers.

twogts4us said:

You cited the limited threads on the Mod Motor, but I fail to see the connection between using a torque wrench and not enough threads..?
I'm sure I'm not the only one who has never used a torque wrench to install their plugs and never had an issue doing so.
Your argument has no merit.

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The connection between applied torque and the number of threads in the head comes down to shear strength and the axial load due to torque. The shear strength is determined by the shear area which is a function of the thread engagement length. The shear area is the helical contact area between mating box and pin threads. As the thread engagement length increases, the shear area will increase.

Torque results in an axial load that puts the box in shear (for this scenario). For a given thread and material, there is a ‘torque to yield’ which is simply the torque that is required to stress the material beyond its yield strength. As we all know, the head is made of aluminum which has a yield strength that is significantly less than the yield strength of steel spark plug threads. If the ‘torque to yield’ is exceeded, the shear strength of the box thread will be reduced. Once the thread’s shear strength has been compromised, the spark plug is more likely to blow out.

Now going back to shear area, a head with greater thread engagement will have a higher ‘torque to yield’ compared to a head with less thread engagement. In other words, the short thread length in the head reduces the amount of torque required to damage the thread.

With that being said, I agree with twogts4us that there is nothing wrong with tightening down the spark plugs by feel. A torque wrench is a safer method for inexperienced mechanics but as a previous poster mentioned, a torque wrench is just a tool and human error is still possible. If a torque wrench isn’t available, tightening the spark plugs 1/16th of a turn past finger tight will get close to the required torque without damaging the threads.

trinity_gt said:

It's funny how the people complaining about the cost of a tool would willingly cough up way more than that to repair a head when a plug blows out.

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What the hell gave you that idea? I don't think there is anyone who 'willingly' coughs up big bucks to repair a head. It may be because they are 'forced' to cough up big bucks, but I doubt they do it 'willingly'. Furthermore, many go the helicoil route, which isn't big bucks.

DIERDORF_237 said:

When did I say I was a genius? That would imply that I already have my degree, but I specifically used the word TRYING. I meant since I'm in school I'm realizing just how difficult engineering is, and have a ton of respect for engineers. Would I like to be a genius one day? Sure. Who wouldn't?

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My answer remains the same - "...Or do you mean because you are going for your engineering degree that you will soon be considered a genius?" It my opinion that the classification 'genius' belongs on those who are far beyond engineers - somewhat equatable to a prodigy. I suppose your definition of genius is different.

DIERDORF_237 said:

They probably fixed the issue because nobody could grasp the concept that a torque wrench might actually be necessary, everybody was so used to ball-parking it. They design something to an exacting standard and everyone throws a hissy-fit so they have to dumb it down because people are too lazy to do the job right.

Do I know that that is what happened? No, but it sure seems likely.

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Really? Do you really think that the big ol' Ford corporation decided to 'dumb it down'. Man, I would have liked to been a fly on the wall during those discussions at FoMoCo.

Metalli485 said:

The connection between applied torque and the number of threads in the head comes down to shear strength and the axial load due to torque. The shear strength is determined by the shear area which is a function of the thread engagement length. The shear area is the helical contact area between mating box and pin threads. As the thread engagement length increases, the shear area will increase.

Torque results in an axial load that puts the box in shear (for this scenario). For a given thread and material, there is a ‘torque to yield’ which is simply the torque that is required to stress the material beyond its yield strength. As we all know, the head is made of aluminum which has a yield strength that is significantly less than the yield strength of steel spark plug threads. If the ‘torque to yield’ is exceeded, the shear strength of the box thread will be reduced. Once the thread’s shear strength has been compromised, the spark plug is more likely to blow out.

Now going back to shear area, a head with greater thread engagement will have a higher ‘torque to yield’ compared to a head with less thread engagement. In other words, the short thread length in the head reduces the amount of torque required to damage the thread.

With that being said, I agree with twogts4us that there is nothing wrong with tightening down the spark plugs by feel. A torque wrench is a safer method for inexperienced mechanics but as a previous poster mentioned, a torque wrench is just a tool and human error is still possible. If a torque wrench isn’t available, tightening the spark plugs 1/16th of a turn past finger tight will get close to the required torque without damaging the threads.

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Amen. And for the record, I use the tried and true method of utilizing a length of fuel line hose to start the spark plug into the threads. You get a very accurate 'finger feel' doing it this way. Then, as soon as the hose begins slipping and the plug is no longer turning, you are essentially finger tight. And I also use anti seize.
You are so right that a torque wrench is a 'safer method for inexperienced mechanics', but you also have to consider that some people shouldn't be using ANY tools whatsoever. Some people just simply have no mechanical aptitude and should keep the hood shut.