Anybody ever seen a mis-sized spark plug gapper?

[ForYourOwnGood]

This morning I went to check my spark plug gap and how the electrodes looked since I am running the FP tune now I wanted to be sure they were all good. I discovered a few strange things along the way, the first being that plug #3 was loose already. When I installed them I used a torque wrench and set the to whatever the value is supposed to be, I can't remember off the top of my head now, like 7 to 10ft-lb? Anyway, not sure how that happened but the gaps were my big concern and how they looked.

I had bought a new disc gapper tool when I put the Brisks in the car and set them to somewhere around .028" or .030", or so I thought. I went to check them and couldn't find that one so I used an older one I had in my tool box. Imagine my surprise when I couldn't even fit .025" in there, the gap appeared to be a little less than .020".

Turns out the little disc gapper I used to gap the Brisks is about .010" too thin after I found it, it was brand new when I used it. I got my dial calipers out and measured it, its thin around the entire diameter. Maybe mis-cast?

I ended up bending one more than I was comfortable with trying to open them back up, so I used a set of brand new Ford plugs that I had spare. What a MASSIVE difference in drive ability. Its like a whole new car at low RPM and off idle from a light, and it no longer stumbles at idle either. What a weird problem. I used to use a feeler gauge set to check my gap but I lost it when I moved, never bought a new one. :frusty::frusty::frusty:

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[jbailer]

Yeah torquing down spark plugs well really relies a lot on feel. I carefully insert the spark plugs down into the hole by putting about a 1 foot long piece of 3/8" rubber fuel line over the end of the spark plug and start threading it using the fuel line. That way I can really feel the threads of the plug. I can also tell if it seems to bind up early. Because it's such low torque to tighten the plugs, you might hit that and not have them fully inserted. This way you get a better feel for the plug going in cleanly until hand tight. Then pull the fuel line off and finish with the torque wrench + socket. If it's questionable like the threads are a little gritty, I've pull it back out and clean the threads, reinsert it and if necessary over torque it to maybe 15 ft lbs, back it out and then torque it properly.

I've never used a proper platinum plug gapping tool. I still use the old method before the tools became readily available of pliers to open them, set them in a vise and tap lightly with a hammer to close the gap.

That really sucks getting a feeler gauge that isn't accurate! I've never seen that before. That far off, closed down would definitely rob you of a lot of power. The trick is to get them open as far as you can without blowing out the spark. From memory, I can't remember exactly where I ended up, I think I am using .030 with the FP tune and stock plugs. Although many people talk about using smaller gaps and colder plugs, I don't think either are necessary or help with the FP tune.

 

[ForYourOwnGood]

Yeah torquing down spark plugs well really relies a lot on feel. I carefully insert the spark plugs down into the hole by putting about a 1 foot long piece of 3/8" rubber fuel line over the end of the spark plug and start threading it using the fuel line. That way I can really feel the threads of the plug. I can also tell if it seems to bind up early. Because it's such low torque to tighten the plugs, you might hit that and not have them fully inserted. This way you get a better feel for the plug going in cleanly until hand tight. Then pull the fuel line off and finish with the torque wrench + socket. If it's questionable like the threads are a little gritty, I've pull it back out and clean the threads, reinsert it and if necessary over torque it to maybe 15 ft lbs, back it out and then torque it properly.

I've never used a proper platinum plug gapping tool. I still use the old method before the tools became readily available of pliers to open them, set them in a vise and tap lightly with a hammer to close the gap.

That really sucks getting a feeler gauge that isn't accurate! I've never seen that before. That far off, closed down would definitely rob you of a lot of power. The trick is to get them open as far as you can without blowing out the spark. From memory, I can't remember exactly where I ended up, I think I am using .030 with the FP tune and stock plugs. Although many people talk about using smaller gaps and colder plugs, I don't think either are necessary or help with the FP tune.

Yeah I've put in hundreds of plugs, I thread them by hand every time until snug. I'm not sure how one came loose because I always make 2 passes over them to double check the torque. Worked in QA too long not to be anal with that kind of stuff.

I've also never seen a gapper be that far off, I'll try and get a picture of it later. The .010" end of it is almost as thin as construction paper which I didn't notice before.

 

[dgc333]

I don't think the manufacturers of those circular gapping tools really expect anyone to use them. They are mostly made as a marketing give away.

 

[MakStang]

For those who don't have a torque wrench (including myself), this is what Adam suggests: Hand tighten the plugs then do a 1/4 turn with the ratchet. If you put the ratchet on and turn it and it becomes "free" again, re-tighten with your hand until you can't turn anymore. Then 1/4 turn.

 

[trippleyelo]

For those who don't have a torque wrench (including myself), this is what Adam suggests: Hand tighten the plugs then do a 1/4 turn with the ratchet. If you put the ratchet on and turn it and it becomes "free" again, re-tighten with your hand until you can't turn anymore. Then 1/4 turn.

Wow mates

Changing spark plugs without a torque wrench is like going fishing
With can and string use the right tools . By the way12lbs is what
the manufacturer recommendation are..

I had one of those rings and they are way off feeler guage is best..

 

[dgc333]

Wow mates

Changing spark plugs without a torque wrench is like going fishing
With can and string use the right tools . By the way12lbs is what
the manufacturer recommendation are..

I had one of those rings and they are way off feeler guage is best..

I have been changing spark plugs for over 40 years and have never used a torque wrench. Never had a plug come loose or had one I couldn't get out.

What I learned early in my engineering career 40 years ago was using a torque wrench to tighten a fastener is only slightly more consistent than doing it by hand. Do to friction in the threaded joint from variations in lubricant, inconsistencies in the threads and/or damage to the threads you can see as much as 40% variation in the clamping force fastener to fastener. That is why critical joints use torque to yield fasteners or measure bolt streach to ensure fasteners are providing consistent clamping force.

I feel perfectly comfortable with the previously mentioned method of run the plug in by hand until it bottoms then add a quarter turn. When tapered seat plugs first arrived on the seen the FSMs used to specify that method for tightening.

 

[TorqueMan]

I feel perfectly comfortable with the previously mentioned method of run the plug in by hand until it bottoms then add a quarter turn. When tapered seat plugs first arrived on the seen the FSMs used to specify that method for tightening.

Not to mention this is an acceptable method for many types of fasteners and fittings used in aviation applications.

 

[TheD-List]

Also, it is important to know that your torque wrench is accurate at such a low torque level. Typically if you're using a torque wrench that is in ft/lbs and didnt cost you your first born, it's probably only fairly accurate at 12ft/lbs. But if you are using a torque wrench for in/lbs and you have converted or are using the value for in/lbs you are probably safe.

Just for reference: 12 ft/lbs is a reasonable estimate for the max torque you could put on a relatively small handled screwdriver if you were tightening a screw down. This is why it is strongly recommended to use the aforementioned technique of hand tight, and then a quarter turn. Probably more accurate than that harbor freight torque wrench you've been letting the kids hit each other with ;)

 

[dgc333]

FWIW, Hot Rod did a comparison of torque wrenches and the $39 digital Harbor Freight unit won the comparison for accuracy and long term repeatability. The comparison included high end units that cost several hundred dollars.

 

[Juben]

FWIW, Hot Rod did a comparison of torque wrenches and the $39 digital Harbor Freight unit won the comparison for accuracy and long term repeatability. The comparison included high end units that cost several hundred dollars.

Yeah, this is true. The HF torque wrenches are pretty good units. HF was running a big sale where you could get them for $13 and we picked up a 1/2 drive model to compare to our Snap-On and Kobalt units we already had. The HF torque wrench was spot on with those two.

 

[trippleyelo]

Not to mention this is an acceptable method for many types of fasteners and fittings used in aviation

If I had any idea that major airlines have a procedure to like above
Mentioned I would not fly.. are you a aircraft mechanic and if you are
we're..

 

[TorqueMan]

If I had any idea that major airlines have a procedure to like above Mentioned I would not fly.. are you a aircraft mechanic and if you are
we're..

Worry not, people a lot smarter than you and me figured out a long time ago that there is more than one way to skin a cat. Here's a tech discussion about achieving acceptable torque on hydraulic fittings on a blog maintained by Parker-Hannifin, a company that manufactures products widely used in the aerospace industry):

http://blog.parker.com/turn-vs-torq...-your-hydraulic-fitting-connections-leak-free

I've also attached a PDF from Aeroquip, another company well known in the aerospace industry. It describes three different acceptable methods for achieving satisfactory torque with their products.

FAA directives list minimum torque specifications for a variety of different components, but also include the caveat that manufacturer specifications take precedence over FAA guidance. That means the TFFT (turns from finger tight) method is perfectly acceptable for achieving proper torque (on those components where the manufacturer allows it).

Here's directions from a spark plug manufacturer:

https://e3sparkplugs.com/torque-chart/

They specify 1/16 TFFT for their plugs unless the engine manufacturer says otherwise.

TFFT has been around a long, long time. You just have to be careful that the threads haven't been boogered up, contaminated with something or that they aren't binding for some reason that prevents you from getting the component (fitting, bolt, spark plug, etc.) all the way to finger tight. It should be readily apparent as soon as you start turning the wrench whether or not you started from finger tight.

BTW, I am not an aviation mechanic, but I did build an airplane and hold an FAA-issued repairman certificate (equivalent of an A&P license) for that aircraft.

 

[HoosierDaddy]

Not to mention this is an acceptable method for many types of fasteners and fittings used in aviation applications.

I heard that is only common among mechanics who never fly.

 

[Juben]

At times when I haven't had a torque wrench readily available, I always went 1/16-1/8 of a turn after finger tight. And like TorqueMan said, you'll usually know if anything is gumming up the threads, etc.

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