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Torque Wet or Dry?

Partly from here

I ’m starting this thread both to keep Peter happy (new threads!) + it relates to the brake Calliper job I am doing in a couple of days.

For example, when I refit spark plugs, following the recommendations from Mike Busch, I always torque wet with lots of engine oil on the threads. I also try to bring things up to torque in one sweeping action as the “stop start” friction on nuts will be a factor if it’s not done in one sweep towards the end.

So this is why “in theory & with no prior knowledge” I would prefer use copper grease on the bolts of my Cleveland brake Callipers but we’ll see what people think? Clearly a lower wet torque would be required but I stress that have not read the manual yet so any comments welcome.

United Kingdom

Archer-181 wrote:

when I refit spark plugs, following the recommendations from Mike Busch, I always torque wet with lots of engine oil on the threads

Even though you mention god-almighty Mike Busch, this doesn’t sound like good advice. Don’t use engine oil on the spark plug threads, they can become virtually unremovable. Use a special carbon based compound designed for that purpose.

https://www.aircraftspruce.com/catalog/eppages/t556sparkaniseize.php?clickkey=112695

Also I have never seen a professional aircraft mechanic use a torque wrench on spark plugs. The range of acceptable torque is so large (check your engine manual, better than the aircraft maintenance manual) that the wet vs dry doesn’t really matter.

Archer-181 wrote:

So this is why “in theory & with no prior knowledge” I would prefer use copper grease on the bolts of my Cleveland brake Callipers

That’s what I see aircraft mechanics use for this purpose.

Also I have never seen a professional aircraft mechanic use a torque wrench on spark plugs

I better hide then All real engineers I have known always use a torque wrench on spark plugs. And all real engineers go around the engine twice, with the torque wrench, without having a conversation while doing it.

I would prefer use copper grease on the bolts of my Cleveland brake Callipers

That’s what I see aircraft mechanics use for this purpose.

If you use copper grease on spark plugs, this tells you who doesn’t do oil analysis

If you use copper grease on spark plugs, you get a huge spike of copper in the oil analysis, equivalent to bush flying in Africa with the alternate door open.

That spark plug lube (there is a Champion version which is probably identical) is the correct stuff to use.

If you strip a spark plug hole, it’s gonna cost you 1000 quid, plus tons of extra avgas burnt over 50-100hrs to bed-in that freshly honed cylinder. Plus, the likelihood that you will lose the balancing which the original builder should have done by matching an underweight piston+pin to an overweight conrod small end.

Administrator
Shoreham EGKA, United Kingdom

I never said to use copper grease on spark plugs, the opposite, I said use the Tempest compound.

I said that I see people use copper grease on break caliber bolts.

Archer-181 wrote:

I also try to bring things up to torque in one sweeping action as the “stop start” friction on nuts will be a factor if it’s not done in one sweep towards the end.

Sounds weird to me. Most things that needs “accurate” torque, also consist of major parts going together using several bolts. The normal procedure is to torque all the bolts in 2-3 steps, increasing torque for each step. For really accurate stuff, you wouldn’t come near it with a torque wrench in any case, as it is not an accurate method of achieving the pre-stress in a bolt. The idea with a torque wrench is to get enough torque so the bolt has above minimum required pre-stress, but not too high so the threads start shedding. That’s all there is too it.

The elephant is the circulation
ENVA ENOP ENMO, Norway

If you strip a spark plug hole, it’s gonna cost you 1000 quid

Is that what they charge for a Helicoil insert these days :-) Only messing … If money was no object you would change the cylinder. I’ve one dodgy spark plug boss and I dread going near that cylinder. I’m all for tempest plug lube and a torque wrench. Even career mechanics can screw up torques, such as the small drain bung on the carb which a common one that gets literally welded in.

Buying, Selling, Flying
EISG, Ireland

I am seeing some misinformation here.

When using a torquing down a bolt, each swing of the wrench from start to finish must have movement. Meaning as you turn the torque wrench, when you start the swing, it must move. If you stop the swing of the wrench before the “click”, the bolt will be under enough load to cause a click when you start turning again. The only time you need to step out a torque is the value is large, say your propeller bolts. Mostly this is the case to not cause tension on the other bolts and everything tightens evenly.

If I may be honest, if the mechanics are not using torque wrenches for your spark plugs, they are no professionals…

I have seen copper lubricant used on spark plugs but its not common. The aforementioned spark plug lubes and anti-seize compounds are designed for this. Use it. Do no use oil on your spark plugs, that is crazy. I would be extremely careful with this. Imagine how much additional torque is being applied to the housing because of this.

My answer of whether to torque wet or dry….What does your maintenance manual want you to do?

From Lycoming Service Instruction No. 1042AC:

Use a copper-based anti-seize compound or engine oil on spark plug threads starting two full threads from the electrode, but DO NOT use a graphite-based compound.

and as long as the copper grease is applied sparingly, and as instructed, I don’t see a lot of it getting into the engine oil.

As for wet or dry, as NJ wrote, RTFM.

Glenswinton, SW Scotland, United Kingdom

Thanks Jacko. Don’t worry, I will RTFM before a do the job! I was trying to open more of a pros and cons debate.

I’m glad the Lycoming manual mentions engine oil! – That’s what my last two maintenance organisations told me to do which is why I was doing it. I do follow the torque in the Lycoming manual and to be honest it never feels tight enough to me! I always check the torque wrench about three times and go around twice (which defeats what I was told about keeping the nut moving until the click). However on the plus side it proves that you have not been distracted and totally missed a plug.

I’ve never had the slightest problem pulling out spark plugs but there again I get to 50 hours quite quickly (and will now be pulling out the top plugs at my 25 hour oil changes). I’ve probably been lucky.

BTW if anybody knows where I can get a decent 6 point 1 inch plug socket (preferably in Europe) please let me know. Mine is a 12 point socket and is far to thick so only just grips the top of the plug. I have to be very careful.

Thanks all who post for your knowledge and such useful information.

United Kingdom

Given that the anti-seize compound is quite slippery, it thus sounds like the spark plug torque is specified “wet”, so putting oil on the thread is probably OK.

That would be the safer way to do it because if you specified it “dry” then any slippery stuff on it would over-stress the threads and there would be many problems in the field.

I used to use copper grease carefully (not in the first 2 threads) and it still got into the oil analysis.

Archerthis post should point to a suitable plug spanner.

Administrator
Shoreham EGKA, United Kingdom
17 Posts
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