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Crud

C

cubdriver

Registered User
Oklahoma
This year at annual, I noticed a lot more build up of crud on the valves, pistons, exhaust and even intake of my cylinders and exhaust system.

It was so bad that the lower plugs were completely full of grit and the exhaust stacks were so crusted that a rotary brush wouldn't scratch it, had to scrape it out the best I could with a knife. Had to stake one exhaust valve to bust up the crud.

Since my overhaul, 4 years ago, I have run exclusively 100 LL and lean a little at cruise. I think this crud is lead residue. Don't know why it would be worse this year than others.

Has anyone else ever experienced this and if so how did you remedy it. I am considering a blended fuel, 50/50 with premium unleaded car gas and/or adding TCP to the fuel.

I would welcome some advice on this.
 
I used to clean my plugs every 50 hrs. because of lead build up. I started leaning all the time even on the ground and I don't have that problem anymore. MMO and TCP also work. I have tried them both. You can tell engines running MMO. You pull a rocker cover or a cylinder and everything is wet.

Steve
 
Interesting. I use to use MMO before the overhaul, mostly in the oil.

Can you mix it in a bulk tank, say 500 gallons? Will it stay suspended?

The TCP people say their product will stay suspended in a bulk tank. I remember as a kid seeing at the auto gas station, that TCP was an addative to Shell gasoline. My dad called iit Tom Cat Piss.

As far as oil additives, what about Avblend. I have been advised to start using it in my oil.
 
Correct me if I'm wrong, but I started using Aeroshell 100 plus in the summer. Someone told me that the -plus indicated that Avblend ( or a similar additive) was included in this formulation.
 
Shell 100Plus Oil

The additive is the one required for certain Lycoming engines, The "H" ones I think. You used to have to put a little bottle of it in at each oil change, the Plus stuff has it in the mix and takes care of that little chore.
 
Avblend seems to do an excellent job of keeping things clean of the crud. The stuck valve problems the training 172's at BRD were always having disappeared once they started using AvBlend.

Brad
 
A couple of years ago, I was getting a lot of crud buildup on the plugs from my Cessna 180. Replacing the plugs with Iridiums seemed to help.
 
Cubdriver......

Cubdriver,
You would do well to switch to auto fuel if your engine is STC'd for it. Auto fuel will substantially reduce deposits and residue due to the fuel. Remember, 100LL IS NOT low in lead. Auto fuel has NO lead. Lower plugs almost never get gooped up using mo gas as well. Also saves money.

Mike
 
I have read that 100LL has 4 times the lead of 80/87?? Does anyone else agree or can confirm this?
 
That is what I was implying. The lower compression engines were designed for 80/87 and if the lead content is 4 times higher in 100LL, it cannot be good for the lower compression engines?? The C-85/90 engines seem really a problem for the high lead content. :drinking: :drinking: that 6% Canadian beer dont make you spell to good or have gooder grammer ider. :D
 
As noted on other posts, though, I'd run a little avgas through the engine, either via mixing auto gas with avgas, or by just running a tank of avgas through it occasionally.

All these engines were designed to run SOME lead, so to "simulate" the lead content of 80/87, you could run 1/3 100 LL and 2/3 auto fuel, or???

The point is, the valve train in particular needs some lead, just not as much as straight 100 LL has.

Auto fuel, as noted, has none.

Also, read the auto fuel stc requirements carefully. They have a lot of caveats.

MTV
 
I find it hard to believe that no one mentioned the fix that doesn't cost a dime. You need to lean the engine more and run a little higher RPM. The lead deposits are typically a sign of running to cool. Heat burns off the lead. The O-300 Continentals are known for sticking valves but this can be fixed with running the engine a little harder. A good tell tale would be your percentage of power and then fuel burn. Compare with other people. You might be a gallon more than your buddies.

A guy in Alaska stuck a valve on his Franklin 165 and no one at Lake Hood would touch it. They all showed him which cylinder it was and said it need to come off, but they wouldn't do it. It finally ended up on my door step and I did 30 minutes worth of rope trick and showed him how to run the engine and he didn't have any more problems. And we never pulled a cylinder.
 
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