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Cleaning Carbon out of Cylinder Head

N

nekit

Active Member
Rebuilding a fairly low time O-320. Wondered if anyone had a trick tool for cleaning carbon deposits in combustion chambers, with the cylinders off the engine. On automotive heads I've used wire wheel and scotchbrite wheels. With the attached cylinder configuration of aviation heads it a little harder.

Any insights on tools or chemicals that help out?
Thanks,
Rob
 
Hoppes won't touch carbon buildup. In fact I find it barely usable on guns. Like the smell though for some strange reason.

Nothing the average consumer can buy from an auto parts store will soften carbon deposits. Been there done that.
 
rocketbob said:
Hoppes won't touch carbon buildup. In fact I find it barely usable on guns. Like the smell though for some strange reason.

Nothing the average consumer can buy from an auto parts store will soften carbon deposits. Been there done that.
Click to expand...

Bob,

Maybe the grocery store . .

In my former employers' development lab, the fuel systems guys used a detergent bath heated to 180F. They used a fancy product, but said they would use Wisk mixed rich with water too when they ran out. It would soften and break loose the diesel combustion carbon deposits on injectors, even in the orifices. I tried this on some parts at home and and it easily cleaned the varnish from lifters, connecting rods etc. It smells up the kitchen.

I might be concerned about aluminum, though, due to the resulting pH. No help to the OP in that regard. YMMV.
 
There are lots of detergents that will work but what effect do they have on the aluminum...that's the thing. Simple Green should work but I'm not sure I would use it. In the shop I have the PPG product and I put whole cylinders in a turkey fryer pot I throw on the stove for a couple of hours, and that usually gets things nice and clean.
 
I have used a heated ultrasonic bath with mild dish soap solution for 15 minutes, then used walnut shell or plastic media in a blast cabinet. Use as mild a solution and as little pressure as possible to accomplish the job.
 
In the world of 2-stroke racing, we used oven cleaner. Takes the carbon right off with very little work.

I have not found any commonly available chemical that does a better job.
 
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Walt,
It is true that basic solutions will attack aluminum, but it takes time for that to happen. It is far from instantaneous.

Same is true for mag wheel cleaner such as Blechwite (very handy degreaser). I have used both for "warned" applications for 30 years on motorcycle guts and exteriors.

The simple trick is to pay attention and don't let the chemicals sit on the base metal (or paint :eek:) for long periods of time. They will stain or etch depending on how long you allow it to sit.
 
rzbill said:
Walt,
It is true that basic solutions will attack aluminum, but it takes time for that to happen. It is far from instantaneous.
Click to expand...

True, but my fear would be having some leach its way into a crevice where it is not easily rinsed out (like between the barrel and head/guide to head/valve seat etc.).
 
Walnut Shells

I think the best option is to blast them with walnut shells or other similar media. Do not use sand. You can look it up in the Lycoming Direct Drive Overhaul Manual. It talks about cleaning carbon deposits. Good luck.
 
One of the things I do after cutting valve seats is fill the cylinder with solvent to make sure the valves seal well, and let them sit overnight. The next day after pouring the solvent out I blow the inside dry and often I will see streaks come from around the valve seats while doing that. The solvent will work in between the seats and the casting. Using something that would cause corrosion there especially between two dissimilar metals is probably not a good idea.

The other thing to consider is most of the deposits aren't carbon, they're lead with a bit of carbon, oil, and combustion byproducts such as sulfur. Most household/shop chemicals won't touch this stuff.

Its not necessary that the cylinders get perfectly clean, because they will get dirty again in short order...
 
McKay Parts Dip. Evil stuff. I wonder sometimes how many years I've cut off my life by getting that stuff on my bare hands back in the day. Sure did a good job on carbon/lead/oil deposits though.
 
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