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Dean Pichon

Well Known Member
I'm doing the first condition inspection since the switch to auto plugs (and PMags). In some cases, the brass thread reducers come out with the plug. Sometimes, the plug comes out and the reducer stays in the engine. So here are my questions:

  • When replacing a plug, do you typically remove both the plug and the reducer and install new crush washers everywhere?
  • If the reducer stays behind, do you remove it to add a new crush washer?
  • When you torque the new plug, what torque is used? I destroyed an insert by attempting to torque it to 35ft-lbs. (There was no plug in the reducer which may have been a mistake.) I destoyed a second reducer when I attempted to remove it from the plug after having removed the plug.
  • Finally, where can I get more reducers and are they all brass?
Thanks in advance for the help.
 
Torque the reducers the same as the original aircraft plugs, which I believe is 25-30 lb-ft? Torque auto plugs 18-22 lb-ft. Use anti-seize on all threads, adapter and spark plugs. Since the torque is so much higher on the sleeves than the plugs, the plugs should always come out first. There's no need to remove the sleeves.

Sounds like you've been overtorquing the auto plugs.

Heinrich Gerhardt
RV-6 w/dual Lightspeed and auto plugs
 
One rule seems to be that the wrong part loosens...

I don't know if the Pmag reducers are the same, but the Lightspeed documentation says 25 ft-lbs for the reducers, 15 ft-lbs for the plugs, IIRC. Be sure to use anti-sieze on both! You can get a bag of copper washers for the reducers from Spruce, and replace them every time the reducer comes out. If the reducer stays put, I simply verify 25 ft-lbs, no reason to take it out.

Even with the torque offset, the reducers will often loosen before the plugs...
 
Torque

Check the manual. I'm at work and can't but I believe the insert is 35 ft lbs and the plugs are 25. I have a small peanut plug that I thread into the insert and use a deep socket to torque. Then I do the plugs. The manual says not to put the insert in without a plug because of potential damage.

I always us some anti seize on the insert and plug.
 
Emag recommends inserting the sparkplug in the adapter and then torqueing the sparkplug, not the adapter, to 15 ft/lbs.

Torqueing the adapter to anything higher w/o the plug inside will crush the adapter.

I suppose you could insert the plug and torque the adapter to a higher value so they say in place when you remove the sparkplug.

When I remove the plugs the adapters come with them. Then I remove the adapter from the plug and put new washer-gaskets in and reinstall them.
 
I should have read the PMag manual first...

After messing up 2 adapters, I decided to review the manual, and found, as previously mentioned, the instructions to install the adapter on the plug and then torque the plug to 15 ft-lbs.

I guess I will accept that the insert will usually loosen before the plug and keep spare crush washers.

Those adapters certainly are expensive...

Thanks for all the advice.
 
As previously posted, Lightspeed recommends 25 lbs for the adapter and 15 lbs for the plugs. I just finished my first condition inspection and the plugs all came out, and the adapters stayed put.
 
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