Changing Spark Plugs; what should I know

[thomas1142]

First time changing the plugs on my 1997 J, anything special I need to know? 

[Andy95W]

Have one of your hangar neighbors who’s done the job check your work.  Take a cooler of beers and sodas out to the airport as payment for his/her time.

It’s a simple job once you’ve done it.  But there are pitfalls if you haven’t.  Proper torque, use of anti-seize, gapping, and not cross-threading are a few.

[N201MKTurbo]

Are you replacing them, or just inspecting, cleaning and gapping them? If you haven’t inspected them, how do you know they need replacing?

[thomas1142]

25 minutes ago, N201MKTurbo said:

Are you replacing them, or just inspecting, cleaning and gapping them? If you haven’t inspected them, how do you know they need replacing?

During Annual I was informed they performing as required, and since then I’ve been having starting issues. So…

[N201MKTurbo]

1 minute ago, thomas1142 said:

During Annual I was informed they performing as required, and since then I’ve been having starting issues. So…

Probably not the plugs.

[KSMooniac]

How many hours on the plugs, and what type/brand are they?  With what they cost these days, I would want to have a compelling reason to change them, especially if you haven't done a full diagnosis yet of your starting issues.  Did your shop measure the resistance of each plug while they were out for inspection? 

If you just want a fresh set because that is what you want, there is nothing wrong with that sentiment.  Especially if you're upgrading to fine wire plugs...   I would highly recommend Tempest for either style.

My biggest bit of advice is to NOT drop them!  Be very deliberate when removing and reinstalling them... if you drop one, throw it away.  Don't look at it and think it is OK for us, just throw it away.  Maybe hit it with a hammer a few times so a frugal Piper owner doesn't pull it out of the trash and try to use it.

Aside from all of that, it is a simple task.  You'll need a torque wrench, appropriate plug socket, proper anti-sieze for the threads, new copper gaskets (unless installing new that come with some), and gap tools.

[EricJ]

5 hours ago, thomas1142 said:

First time changing the plugs on my 1997 J, anything special I need to know? 

Here's the latest Tempest Installation and Maintenance Manual Guidance which has a wealth of info on handling aviation spark plugs:

https://tempestplus.com/wp-content/uploads/2020/12/1710A_Rev-E.pdf

I think Champion may have a similar document.

Edit:   Here's Champion's equivalent doc, which also includes oil filter handling:

https://www.championaerospace.com/wp-content/uploads/2015/06/AV6-R-Aug20141.pdf

[GeeBee]

Two words. Fine wire.

[toto]

17 minutes ago, GeeBee said:

Two words. Fine wire.

+1

Tempest fine wires were a game changer for me. 

[LANCECASPER]

1 hour ago, GeeBee said:

Two words. Fine wire.

I'll add one word . . lol. Tempest Fine Wire

[Hank]

3 hours ago, bluehighwayflyer said:

It is a very easy job.  Just follow the advice here.  Torque correctly and don’t get carried away the anti seize.  The special wrench for the leads is nice but not required.  

On a J I would install Tempest fine wires, though. They are spendy but worth it for improved LOP ops and should last the life of the engine.  

I recently changed from the copper-based stuff in a 1 lb jug with a huge brush that makes a big, goopy mess on the plugs to this. The brush is more like a fingernail polish brush, and permits good control of the amount and exact location of the compound. 

Too much of the thick copper paste will interfere with good cylinder function. That can't happen with this little bottle of secret sauce that I ordered from Spruce. 

Use a new copper qashwr, torque them properly and DON'T DROP THEM! Every oil change, rotate them top to bottom in the same cylinder, after cleaning,  gapping and testing.

[ZuluZulu]

Make sure your torque wrench has been calibrated recently so you know you're using the right numbers.

[thomas1142]

I have Tempest Fine Wire. Thank you all for the advice.

[Fly Boomer]

8 hours ago, thomas1142 said:

First time changing the plugs on my 1997 J, anything special I need to know? 

Because our plugs are shielded, you may need a specialized socket like this

https://www.aircraft-tool.com/shop/detail.aspx?id=ATS950

[PT20J]

Fine wires have gotten really expensive. They have two advantages over standard massive electrode plugs: They last longer, and the electrodes are more exposed so that they often improve starting and LOP operation and don't oil foul as easily. You get the second advantage with BY extended electrode plugs plugs without the cost of fine wires, but there is more maintenance because you need to gap them every annual and they don't last as long.

[PT20J]

1 hour ago, Hank said:

rotate them top to bottom in the same cylinder

This is only true if you have a Bendix dual magneto. If you have two magnetos, you should rotate plugs between cylinders in the firing order. This is because the magnetos fire every other plug in rotation at the opposite polarity. If you keep them in the same cylinder, then one electrode (center or ground depending on polarity) will wear more than the other. Rotating them evens out the electrode wear. Rotating top to bottom isn't strictly necessary, but helps with a cylinder that is burning a bit of oil since the bottom plugs get the most carbon deposits. On a four cylinder engine, I find the quickest way to rotate the plugs is to put them in the plug tray in the position removed and then swap them crossways: 1T-4B, 4T-1B, 2T-3B, 3T-2B.

Skip

[M20F]

Lots of advice, the key question sort of was asked.  Why are changing your plugs?  Generally there isn’t a need to change all the plugs anymore than change all the cylinders. 
 
Why are you changing all your plugs?

[Beard]

I changed the plugs in my 84J a few years ago with Tempest fine wires, but only changed the bottom ones. The flying school at my home field only uses fine wires on the bottom clyinders on their twins as they are the ones that foul. I know this sounds cheap, but my J runs very well on just the bottom one changed to fine wires.

[N201MKTurbo]

I run Autolite SH260s I think they run better than fine wires. I buy them on EBay when I can find a good deal. All new old stock. Too bad they don’t make them any more. Most I pay less than $10 each.

[ArtVandelay]

How long do massives typically last?

[EricJ]

3 hours ago, Beard said:

I changed the plugs in my 84J a few years ago with Tempest fine wires, but only changed the bottom ones. The flying school at my home field only uses fine wires on the bottom clyinders on their twins as they are the ones that foul. I know this sounds cheap, but my J runs very well on just the bottom one changed to fine wires.

I do the same, as I think do a lot of people.    The fine wires in the bottom totally cleared up a fouling issue I had, so they've been great that way.   I still run massives in the tops.

[EricJ]

48 minutes ago, ArtVandelay said:

How long do massives typically last?

Seems like a few hundred hours to me before they won't pass the go-no-go gauge any more.    Maybe 400?   YMMV.

[ArtVandelay]

Seems like a few hundred hours to me before they won't pass the go-no-go gauge any more.    Maybe 400?   YMMV.

Mine have 460 hours and just passed my annual, guess I’ll plan on replacing them next annual.

[EricJ]

2 hours ago, ArtVandelay said:

Mine have 460 hours and just passed my annual, guess I’ll plan on replacing them next annual.

Maybe they'll go much longer!   As long as they're good there's no reason to swap them out, and they're easy to test during cleaning, inspection, etc.

[N201MKTurbo]

7 hours ago, EricJ said:

Seems like a few hundred hours to me before they won't pass the go-no-go gauge any more.    Maybe 400?   YMMV.

I believe the no go gauge is a scam to sell more spark plugs. Is that gauge mentioned in any ICA?

When the side electrodes get down to about 0.020 thick I replace them because they may overheat and cause pre ignition. The center electrode doesn’t really matter, even when half way gone there is plenty of meat there. I have ran massives over 1000 hours with no issues.

Thats one thing I like about the SH260, they have massive side electrodes.