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Spark plug life in terms of TBO

maus92

Well Known Member
I'm pretty sure that my plane has its original spark plugs installed when new in 1999 - some flavor of Champions standard with O-360-A1A. I was wondering if there is some sort of time-based life associated with the plugs. Hour-wise is OK with about 330 hours. They have been rotated several times according to the logs.
 
300-400 hours is about when most Champion massive electrode plugs start to get high internal resistance and start showing lots of center electrode wear. I have seen people run them a little over a thousand hours a few times, but they were completely shot and caused rough running and starting issues due to internal resistor degredation. Do youself a favor and buy the Tempest brand plugs if you think you need new ones.
 
I ran stock Champions over 1,000 hours. As Mike noted there was considerable degradation on center electrode. Then I switched to Tempest and have almost 500 hours on a set of 8. They show some wear but still running strong.
 
Thanks. I reread my initial post, and I wasn't clear about what I was asking - although you have answered a part of what I was after. I think these are the original plugs, which makes them 15 years old. Seems to me that their age makes them a candidate for replacement (although at 330 hours they *might* still be OK.) From the two answers so far, it looks like they could last for a couple hundred hours more, but due to Champion's quality issues, it may be a logical time to replace them - does this seem like a prudent course of action?
 
15 years ago Champion made a darn good product... just not so good in the last 5 or so. If the plugs test and pass, fly'em. :)
 
15 years ago Champion made a darn good product... just not so good in the last 5 or so. If the plugs test and pass, fly'em. :)

I personally wouldn't go as far to say Champion made good plugs in the past. I have cut open a few (two or three) plastic sleeves with brand new REM-40E plugs to find them with no threads! I have also seen many cases where the insulator housing portion of a Champion plug was swaged into the lower half at such and angle where a plug socket would barely fit over the plug.

When I was a boat mechanic we used to buy Champion plugs by the gross (24) and out of any given box of 24 we would have at least two that were bad and would not fire under compression and would cause a dead cylinder. We switched to NGK plugs and never had anymore issues.

The Unison aviation (AutoLite) plugs were a huge improvement over the Champions, but they had some really crappy nickel plating that corroded pretty quickly. Tempest (Kelly Aerospace) bought the product line from Unison and restarted production and they now are being produced with a much better nickle plating finish which does not corrode nearly as bad.

Check you're plugs resistance and electrode erosion to determine their condition. From my experience, the center electrode can actually be worn to, or even beyond service limits without causing performance issues such as rough running or hard starting. When the internal resistance or electrical insulation begins to degrade is usually when you start to have intermittent cylinder misfire and starting issues.
 
What I've gathered from the answers so far is that there really is not a time limit in term of years in service for Champion spark plugs, but I should at least check their resistance. I have the bottom plugs out now because I'm changing the CHT sensors. On inspection, I've noticed no wet oil, one for them had grayish ash, two of them whitish ash, and the forth I'll have to go back and check. I did notice on one of them a "chunk" of white material way deep in the electrode side of the plug, which I *thought* might be lead. I'll have to dig it out with a dental pick to see what it really is - hopefully not a piece of insulator. The electrodes themselves seem to be in good shape, i.e. no visible pitting or erosion. I'm also reading that a standard shop multimeter is OK to use to check resistance? Thanks!
 
I feel like this is overthought a TON with everyone worried about internal resistance. I've run Champions and Autolite/Unison/Tempest plugs for thousands of hours (2000 in some cases) in various applications with no issues. Keep them clean (50hrs) and test them regularly with the Champion cleaning/testing box.

If you want fine wire, I've seen a major quality issue with Champions, but the massive have been fine. I have a 20 year old set in my Citabria right now, bomb test fine, and run great.
 
I feel like this is overthought a TON with everyone worried about internal resistance. I've run Champions and Autolite/Unison/Tempest plugs for thousands of hours (2000 in some cases) in various applications with no issues. Keep them clean (50hrs) and test them regularly with the Champion cleaning/testing box.

If you want fine wire, I've seen a major quality issue with Champions, but the massive have been fine. I have a 20 year old set in my Citabria right now, bomb test fine, and run great.

A multimeter is much cheaper than a pressure test chamber! The pressure test chamber and a multimeter accomplish the same check in different ways.
 
My Propeller balance problem went away after I found a high resistance Champion plug! :rolleyes: (I estimate that plug is 40 years old, still looks good)
I keep that (NG marked) plug for 'show & tell' so other aviators can see a practical resistance test and learn how to do it.
New Tempest plugs are very nice, but I've picked up a set of adapters, some MSD plug cable and boot ends, and read the G3i website on converting a mag harness. I'm about to go to 'the dark side' and try auto plugs.
 
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