Exhaust Guide Cleaning

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proppastie

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I need to de-coke my exhaust guides again.....my IA has died....he had a brass expanding ream to do the job...I can not find one. there are piloted cutting tools for the job at Mcfarland, there are also expanding cutting reamers at reasonable costs.......I was thinking maybe a flex-hone
https://www.amazon.com/12-7mm-Flex-Hone-Cylinder-Silicon-Carbide/dp/B002T0AX6U
might work well, or a brass brush https://www.grainger.com/category/cleaning-and-janitorial/cleaning-supplies/brushes/pipe-and-tubing-brushes?attrs=Bristle+Material|Brass&filters=attrs&ef_id=EAIaIQobChMIn4jBwtmh6AIVJYFaBR0yBgihEAAYASAAEgLzRfD_BwE:G:s&s_kwcid=AL!2966!3!317451745872!b!!g!!&cm_mmc=PPC:+Google+PPC......any thoughts?
 

delta

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I find your post confusing because either your guides are worn or not. Does the valve wiggle in the guide more one way than another? There shouldn't be any carbon buildup on the inside of the guide anyway. You do not want to do anything to increase the tolerance between the valve and guide. They have knurlers that create valleys and hills in the guide that can then be reamed to the correct diameter. I'm not sure if it's advisable to do that more than once however. Sounds like you need to get a few gear heads involved and come up with a second opinion, because mine involves changing 'em out.
 

TFF

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The Lycoming bulletin has the proper ream size needed for each engine. Buy the ream that pulls the debris toward the handle. Grainier has them. Newer guides are looser than older ones to help prevent sticking , so the ream may be loose, which is good.
 

proppastie

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Sounds like you need to get a few gear heads involved
that is the reason for the post.....

I have not done the wobble test.....I have had this problem before and know what it feels like. Changing the guides are a cylinder overhaul because no cylinder shop that I talked to when I did my overhaul would just change the guides, and it is not an easy job in a Lycoming.

After I posted I took a ride and talked to a flight school mechanic, and he used the flex-hone. said you can screw up a guide pretty easily with the cutting tools....

Anybody ever use a brass brush ?... the idea not to remove any metal from the guide.
 

TFF

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Brass brush is ok. Just don’t get bristles down in the cylinder. The ream of the correct size only knocks out carbon. If the ream goes through the valve should. Ream is designed to be fool proof where a brush you have to make sure it’s clean. If it is cutting into metal, something else is going on.
 

proppastie

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is there a good solvent (Marvel, Hopps) ? will help with the carbon?
 

proppastie

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If it is cutting into metal, something else is going on.
I read if the carbon holds it off on one side it could cut metal on the other side. .....but I agree the proper piloted reamer should work well.
 

proppastie

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I have never had a stuck valve. I have used Marvel Mystery Oil in the fuel since about 1970.
I have only had one once....what is going on now is rough running and not able to reach peak rpm until the engine is very warm....and taking longer. It used to be when everything was in the green I could apply full power and the engine would go to 2650 (constant speed prop) and not be rough. Lately it has required 2 full power run-ups after it was well into the green....When it is hot I do not have this problem. Very annoying, and now that it is warm I have decided to try to fix it.
 

Pops

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I have only had one once....what is going on now is rough running and not able to reach peak rpm until the engine is very warm....and taking longer. It used to be when everything was in the green I could apply full power and the engine would go to 2650 (constant speed prop) and not be rough. Lately it has required 2 full power run-ups after it was well into the green....When it is hot I do not have this problem. Very annoying, and now that it is warm I have decided to try to fix it.
Have you cleaned the plugs ?
 

proppastie

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Just had them out for injecter cleaning and new crank seal. They looked ok but that's a good idea.
 

dino

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Seafom has worked well for me. Try a Megadose initially by direct intake injection,
 

proppastie

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pretty sure it is not the fuel system.....was looking for something to dip the brass brush in or loosen the carbon in the exhaust guides after I do the rope trick and have dropped the exhaust valve into the cylinder....I would think anything in the fuel would be burned up by the time it gets to the exhaust stem and guide. There is some though to soaking the exhaust guides ........is that what you meant by direct injection?....Would be great if I could pull the valve covers, squirt Seafom or Marvel and it would loosen the carbon and next time I run the engine it would flake off,....without going to the trouble to drop he exhaust manifold and do everything that needs to be done in order to clean the guides on the engine.
 

TFF

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I Have never found anything special for cleaning carbon. I find whatever you spray in acts more as a wash for the brush or tap or whatever you put in. I always do it dry with the tap and then clean. I can see better that way. It’s not going to matter one way in the end if it’s krull or mineral spirits or LPS or whatever. It’s hard crunchy stuff that does not dissolve. It just floats away when chipped at.
 
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