TCM O-470 Spark Plug Lead Fouling

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Denis17
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TCM O-470 Spark Plug Lead Fouling

Post by Denis17 »

Hey guys,

What is your experiences regarding moderate to severe lead fouling on bottom spark plugs :?:
I am working on a TCM O-470 annual inspection. 100 flight hours since last spark plug service. Engine MAG drop was normal at 75 R and 75 L . However, the considerable amount of lead buildup on the bottom spark plugs caught my attention.
What is the cause of this condition :?: I am wondering if this is an issue and whether to consider installing warmer plugs to prevent lead build up :!:

Please share opinion, experience or fact !!!




P.S. I will post picture and plugs P/N as soon as practical.
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photofly
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Re: TCM O-470 Spark Plug Lead Fouling

Post by photofly »

How about teaching the pilot to use the red mixture knob properly?
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TeePeeCreeper
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Re: TCM O-470 Spark Plug Lead Fouling

Post by TeePeeCreeper »

photofly wrote:
Sat Mar 14, 2020 6:26 pm
How about teaching the pilot to use the red mixture knob properly?
You took my breath away. Why pilot owners don't know more about this is beyond me!
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J31
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Re: TCM O-470 Spark Plug Lead Fouling

Post by J31 »

Denis17 wrote:
Sat Mar 14, 2020 6:18 pm
Hey guys,

What is your experiences regarding moderate to severe lead fouling on bottom spark plugs :?:
I am working on a TCM O-470 annual inspection. 100 flight hours since last spark plug service. Engine MAG drop was normal at 75 R and 75 L . However, the considerable amount of lead buildup on the bottom spark plugs caught my attention.
What is the cause of this condition :?: I am wondering if this is an issue and whether to consider installing warmer plugs to prevent lead build up :!:

Please share opinion, experience or fact !!!




P.S. I will post picture and plugs P/N as soon as practical.
Maybe check to make sure they have the correct spark plugs installed. However 100 hours between plug cleaning is a non issue. Clean them up, rotate top to bottom. Suggest to the operator there should be more aggressive mixture leaning both on the ground and in flight.

Heck the 0235 gets plug cleaning every 25 hours and it was built for 100LL!
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Denis17
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Re: TCM O-470 Spark Plug Lead Fouling

Post by Denis17 »

Hey Guys,

Thanks for the input!
The plugs are RHB32E. Below is a picture to get a better idea:
https://photos.app.goo.gl/bBGRiE6dYEkW61my9

I'll clean the plugs up and remind the pilot to use the mixture knob :D
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iflyforpie
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Re: TCM O-470 Spark Plug Lead Fouling

Post by iflyforpie »

I found that doing plugs every 50 hours rather than ever 100 hours got rid of 99% of the problems. Even with aggressive leaning, due to the poor distribution of the O-470 intake manifolds you’ll always get fouled lower plugs.

Also check your primer. Sometimes they leak.

But yeah.. lean on the ground, lean in the air, climb lean, descend lean, land lean. Never had any problems with CHT or burned valves and we all know that TCM leak down values are bunk. If it’s the 230 HP O-470 it’s so derated in comparison to other versions that it’s practically idling at “full power”.
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