Avgas and spark plugs

[BrendAn]

Pulled the plugs out of the 618 for an inspection today and got a fright.

Plugs have a build up of a whitish colour material on them.

Thought I was losing material off the pistons for a second.

Then it dawned on me. Is this lead from avgas. I have run on avgas the last few tanks  because I am too lazy to fill my Jerry cans.

Checked the rave valves ,they slide smooth and easy.

Next weekend I will remove the exhaust and have a look at the rings.

Spark plugs are iridium and have done 43 hours. Look like new again after a quick brush.

All 4 plugs were identical so I take it that's a good sign.

Edited 17 hours ago by BrendAn

[T510]

Make sure you use a soft brush, you don't want to damage the electrodes.

 

Avgas is known for lead oxide deposits building up, it is conductive and can cause misfiring issues. 

There are additives that can reduce it but I always preferred regular checking and cleaning.

 

All 4 plugs being identical shows that the mixtures/fuel burn characteristics are consistent across both cylinders

Edited 17 hours ago by T510

[BrendAn]

2 minutes ago, T510 said:

Make sure you use a soft brush, you don't want to damage the electrodes.

 

Avgas is known for lead oxide deposits building up, it is conductive and can cause misfiring issues. 

There are additives that can reduce it but I always preferred regular checking and cleaning.

 

All 4 plugs being identical shows that the mixtures/fuel burn characteristics are consistent across both cylinders

I started getting a bit of rough running at 3000 rpm and I think this was the cause . I let these plugs run longer being iridium. Now I  will pull them for a clean each 25 hr service and they should good.

[T510]

Idle and low load engine speeds cause a more rapid build up, a good hot run will help keep them clean

[onetrack]

You got it in one, lead fouling. That's pretty severe fouling. Lacquer thinners is a good spark plug cleaner, but I find sandblasting with fine garnet works best. Make sure there's no garnet trapped down the side of the insulator when you've finished.

 

Wire brushes don't clean off deposit coatings properly, and they can leave metal streaks on the insulator, leading to tracking. This bloke has a good video showing spark plug cleaning.

 

 

 

[facthunter]

Anti scuffing additives in the Oil can short out plugs also. Get an old style Hairpin and carefully grind a chisel Point on the longest arm and use that to scratch the deposit from all of the electrode surface.  Use anti seize on the Plug threads. Nev

[BrendAn]

I think I will switch back to 98 from the servo.  The avgas Bowser is too easy.

Traralgon has a Mogas Bowser but we only have avgas at West sale.

Not enough aircraft here to make it viable.