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What spark plug tools do I need?

kcameron

Well Known Member
I'm want to clean and regap or replace the spark plugs on the RV-4 I bought a couple of months ago. This is my first airplane and I've never worked on this stuff before. I've perused Aircraft Spruce's sparkplug tool offerings but I'm not sure what's really needed.
The engine is an IO-360-A1B with dual slick mags. The plugs are Champion REM38E.

Here's a breakdown of the issues I can think of:

Socket:
Is 7/8" the correct size?
ACS sells this one for ~$50:
http://www.aircraftspruce.com/catalog/topages/gapsettingtool5.php
Is there a more reasonably priced aircraft plug socket?
Can I just use a standard deep socket?​
Cleaning:
Does the "clean screen" work? http://www.aircraftspruce.com/catalog/topages/gapsettingtool6.php
or should I resign myself to setting up a sandblast type cleaner in the hangar (including air compressor)?
Gap adjustment:
Wire type feeler gauge or flat?
Do I need special gap-setting tools such as these?
http://www.aircraftspruce.com/catalog/topages/precisegap.php
http://www.aircraftspruce.com/catalog/topages/electrodespreader.php
Thread protection:
Do I need a thread chaser?
Do I need to use thread antisieze?
Any tips or guidance about standard practices would be appreciated.
E.g.: Do I need to use a torque wrench? I never bothered when working on auto or motorcycle engines but maybe it's more critical on a Lycoming.

Thanks,

Kev
 
To properly maintain your plugs you will need, at a minimum:
7/8" deep socket. If you have access to all the plugs, this is all you need. Sears sells really nice ones. You can also get one with a hex end so as to put a wrench on it for hard to get plugs, behind the baffling where the socket wrench and extension won't fit.
A gapping tool to regap the plugs.
A gauge, either wire or flat, but I prefer the wire type sold by Champion, etc.
A plug holder to hold them all in order when you have them out. (You can make one of these or buy any of the types available.)
I use a cheap spark plug sand blaster. You can get these from Harbor freight for about $10 and they work great.
An air gun to blow out the grit.
Some kind of pick to get inside the plug for any lead deposits that need to be removed.
Anti siezee for the threads when you replace the plugs.
Some people replace the copper washers each time they remove and replace their plugs....you decide.
There's nothing special going on here, so you don't have to spend $50 for a plug socket. The gapping tool and gauge are rather specific, but other than that just get good local stuff.
That's my opinion, anyway.
 
A 7/8 deep socket is fine.

If you use Unison plugs, they are a bit shorter than the Champions, and you can cut the deep socket down in length.

If you do this, you can usually use a standard torque wrench, and still get it inside the baffles on the #4 cylinder.

gil in Tucson
 
A few other points

You need a special tool to adjust the gap. Spruce sells several types. You can't just bend them like on a car. And don't use automotive anti-seize. You need the graphite-based stuff that you paint on the threads. Spruce sells Champion's antiseize. Stay away from the last two threads.

You'll need a torque wrench. Aircooled engines run much hotter than the automotive engines you're used to and you can easily wind up with a plug that can't be removed if you don't use antiseize and a torque wrench. The recommended torque is 35 ft-lbs.

You're supposed to replace the copper gaskets every time you replace the plugs. They work by being a soft metal that can be squeezed to form a seal. Once they've been work-hardened, they don't seal as good.
They're cheap. Or you can reuse them if you heat them up with a torch until they're cherry red and let them cool naturally.

Be aware that the gap guage Spruce sells, with what they call the "standard sizes", is probably wrong for your engine. I discovered this the hard way and wound up with fouled plugs. Their "standard" guage is two wire feelers, with a .014 on one end and .018 on the other. The idea is that you tighten down to .014, it springs back to about .016, and you verify with the .018. The problem is (according to the A&P who helped me straighten out my problems), the plug gap (at least on my engine, according to him) should be .020 minimum.

Now here's the amazing thing -- nobody seems to know exactly what the gap should be on any given aircraft engine, including Lycoming. Well, I suppose Lycoming must know, but it's apparently a state secret. Good luck finding a publication that tells you what to use on YOUR engine. It's certainly not in the owners manual. So you just have to ask around and see what other people use. You'll find that every one you talk to knows the exact correct answer -- but none of them agree (sort of like religion). Fortuanately, aircraft engines seem much less effected by plug gap than cars (unless you set it so narrow that they foul, like me). I flew my plane for 200 hours without changing the gap because I couldn't decide what to set it to. Then, I decided to use Spruce's recommendation and wound up with fouled plugs. Incidently -- there's no good way to enlarge the gap by bending. I used some emery cloth and just ground off about a 100 hours of useful life to get them to .020.

A dental pick is handy for digging the lead chunks out from around the insulators. A piece of safety wire works, but not as good. Be careful, you could probably break the insulator and not know it. It's hard to see the lead all the way down at the bottom, but you can feel it as you run the pick around the insulator. Oh, and by the way, get yourself one of those spark plug holders to keep them in while you're working on them. If you drop one, you have to throw it away -- and they cost about $15 apiece. And when you blow the plug out, use a mask. Most of the dust that comes out is lead.

When you put them back in, rotate them. You'll find about a dozen different rotation methods out there. Another religious issue. I personally go top to bottom, then bottom to next cylinder top. You need to rotate them because the lower plugs are worked harder and get dirtier than the uppers.

Oh, one last thing that I learned recently. When you have a plug that isn't firing, you can tell be looking at it. It will be oily! Yes, that's right, aircraft engines have so much blowby even when they're in good shape, that you can see it on the plugs because the oil won't be burnt off! I freaked. If it had been my truck, I would have been shopping for a new truck the next day. But I whipped out my compression tester and it was 74/80. The A&P said it was perfectly normal to see oil on a bad plug -- in fact, that's how you diagnose it.

Welcome to bizzarro world of aircraft maintenance, where engines are designed to burn oil, brake fluid is flammable, most of the technical data is word-of-mouth, and what you don't know can kill you! :eek:
 
Spark plugs

How long should spark plugs last ? I have an RV6 with a O-320 B2C which has done close on 400 hours over three years. Hot starts have been a problem with this motor. Otherwise the engine runs smmothly. The plugs have been serviced annually at inspection time i.e. twice in 400 hours. Should the plugs be change and will this make starting easier ?

Thanks

Mervyn
 
YES, you need a torque wrench. And a std. deep socket will work. (50 bucks for a "spark plug socket"???)
Yes you need Champion anti-sieze.
Yes you need a gapping tool. Avery has one for a little less than ACS, but the ACS one has ball ends on the screws, nice feature, but you can grind your own on Avery's. If you're very careful, you won't need to expand the gap. Sucks if you do. I saw the "spreader" you linked to...but I'm not sure how it's used. The one time I pushed one too far closed, I just inserted the plug into the gapper tool, put the tool in the vise and tapped lightly with a screwdriver. It worked, but it's scary. Better to under tighten originally and check regularly when gapping!

As has been said before...if you drop it...throw it away.

I use .016 gap on my Unisons, same as I used on my Champions...I'm happy with the results. Your mileage may vary.

Jeff
RV4 Toucan
 
I'm sorry, but that's also a state secret. <g>

Wenjosa said:
How long should spark plugs last ?

Seriously, I've asked that question all over the place for the past 7 years that I've owned a plane and have never gotten a straight answer.

I just replaced one of mine at 250 hours. On the other hand, my previous plane, a Cherokee 140, had 600 hours on the plugs when I sold it, never fouled a plug so bad I couldn't blow it out in the runup area, and all I ever did to the plugs was dig out the gigantic lead deposits every 25 hours.
 
Thanks for the great info, guys. Lot's of tidbits there I wold have never thought of or would have had to learn the hard way. I love this forum!

What torque should I use for the plugs?
I've always used Chilton or Haynes manuals for basic (or not-so-basic) instructions when servicing cars and motorcycles. Is there something like that for Lycomings?

Thanks again,

Kev
 
Plug stuff

I've read that Hopps #9 solvent is good to clean lead deposits from plugs, but haven't tried it. Does anyone have any experience with this? How did it work?

Glenn
 
My Lycosaurus book says 35 foot/lbs. (O-360-J2A)

A bag of 100 gaskets is CHEAP, don't re-use. I tried the crush type once, but crush type gaskets use a different torque than the solid copper, don't know what it is, and you don't really need them.

Jeff
 
It's based on wear of the electrodes, not time. If the center electrode is still relatively roundish, and there is no excessive wear on the side ones, you're good to go. The contact area inside the barrel should not show excessive signs of arcing, but you can usually clean that out, try a pencil with a fresh eraser chucked in a drill.
There are also testers for plugs. Sometimes the problem is internal.

Jeff

Wenjosa said:
How long should spark plugs last ?
 
Seriously, I've asked that question all over the place for the past 7 years that I've owned a plane and have never gotten a straight answer.

I just replaced one of mine at 250 hours. On the other hand, my previous plane, a Cherokee 140, had 600 hours on the plugs when I sold it, never fouled a plug so bad I couldn't blow it out in the runup area, and all I ever did to the plugs was dig out the gigantic lead deposits every 25 hours.

I was given a hint on this when a Mech helped me check my spark plugs:


If my terminology isn't correct - apologies.

He had a piece of metal with a hole drilled in it. If the electrodes can fit into the hole, toss the plug. Naturally I didn't have the native wit to ask what size hole that is but I'll see him next week.

Now...

The center electrode starts out being round. As you use the plug it turns more and more into a football shape - the sides of the center electrode are reducing.
In order to get the proper gap, you are repeatedly moving the outer electrodes in towards that receding center. Eventually you will move them in far enough such that the end of the plug will fit into that hole in the piece of metal.

Then you toss the plug.
 
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YES, you need a torque wrench. And a std. deep socket will work. (50 bucks for a "spark plug socket"???)
Yes you need Champion anti-sieze.
Yes you need a gapping tool.
As has been said before...if you drop it...throw it away.
I use .016 gap on my Unisons, same as I used on my Champions...I'm happy with the results. Your mileage may vary.Jeff RV4 Toucan

This is the plug socket to get http://www.aircraftspruce.com/catalog/topages/ATSmagSocket.php?clickkey=7011 Yes, it's $25, but 1) it fits all aviation plugs (most hardware store sockets don't due to a ridge in them and it's 3/8" drive), 2) the magnet is a big help in drop prevention (one dropped plug and you've spent as much as the socket costs)

The Champion anti-seize is very thin and messy. It easily runs in to the plug, causing misfiring and ruins the plug. A thick, nickel based anti-seize is much better. It is also great for exhaust systems (joints and nuts) and makes removal a breeze.

Asking good questions like this will serve you well.

George
 
I'm with George (above) also, get out your trusty Ohm Meter and measure the spark plug resistor. Put one probe down in the top of the plug, and the other on the center electrode. File or sand the center electrode to get a good electric contact where you touch the probe to it.
The resistance should be (??) 1000-1500 ohms new, and the cut off point is 5000 ohms. High resistance causes problems. Here is a link:
https://www.qaa.com/resource-center...s-the-right-way-to-check-spark-plug-resistors
http://www.vansairforce.com/community/showthread.php?t=155929&highlight=spark+plug+resistance
I have removed the internal screw in a Champion plug suffering infinite resistance, the spring and resistor come right out. I cleaned out the plug interior, the spring and the resistor and reassembled. It then checked fine. I'm chicken to run it, but it was a learning experience.
 
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My Lycosaurus book says 35 foot/lbs. (O-360-J2A)

A bag of 100 gaskets is CHEAP, don't re-use. I tried the crush type once, but crush type gaskets use a different torque than the solid copper, don't know what it is, and you don't really need them.

Jeff

35 is what I read and what I heard as well.

Yet the A&P who replaced two of my plugs insisted that 32lbs was better. He maintains an FBO/flight school fleet of airplanes and that's what he always used - 32lbs.

I wonder about that.....
 
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