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Unread 05-16-2013, 02:41 PM   #1
AVR2
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Two possibly dumb questions about pistons/cylinders

I'm about to start cleaning up my piston tops. It's OK for me to turn the crankshaft by hand in order to bring each piston to the top of its cylinder and make it easier to clean, correct?

And once I'm ready to put the head back on, should I give each cylinder bore a coat of oil?

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Unread 05-16-2013, 02:44 PM   #2
gearheadnick
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Yes and yes. You don't want a lot of oil in the cylinders, just a thin coat. And use brass tools on the pistons so you don't gouge up the aluminum.
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Unread 05-16-2013, 02:49 PM   #3
AVR2
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Cool, thanks.

Any recommendations for carbon-removing solvents?

EDIT - I can't find any brass scrapers locally, but I have got some stiff brass cup brushes which I use in my drill. Are they safe to use on the pistons?
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Unread 05-16-2013, 04:18 PM   #4
ratmonkey
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soak in seafoam or kerosene. use brass or stainless wire brushes. never scrape or use power tools.
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Unread 05-16-2013, 04:30 PM   #5
jm8881
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Quote:
Originally Posted by ratmonkey View Post
soak in seafoam or kerosene. use brass or stainless wire brushes. never scrape or use power tools.
I cant say anything for kerosene but seafoam works amazing for soaking into the carbon stuck to the top of a piston. I used it on my mothers plymouth breeze when I did the headgasket.
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Unread 05-17-2013, 04:08 AM   #6
gearheadnick
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Either solvent will work, just make sure you do an oil change since some of it is bound to get by the rings while cleaning.
I don't even remember where I got my brass scraper, but it came in real handy for the tough deposits. Short of that, a hard plastic scraper, even a homemade one, with a good edge would help the tough spots. Just be careful when scraping.
The brass brush in a drill should work, just go easy with it. Try it lightly in the center of a piston and see how it works. You're not going to need a lot of pressure, especially if the carbon has been soaking. I would try a brass hand brush first, and go to the drill if you find hard stuff.
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Unread 05-17-2013, 09:41 AM   #7
zjosh93
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As long as you are just cleaning the tops of the pistons you don’t need to worry too much about small nicks, scrapes and gouges. It used to be fairly common practice for high performance shops to hand fit domed pistons to a combustion chamber using a safe edge bastard file. A lot of people will clearance a piston for larger valves using a dremel. Shops will routinely mill a piston face down a few thousandths to set the piston relief and quench volume. Heck, I’ve seen engine rebuilding books recommend stamping the piston number in the piston face during disassembly. If you want to ceramic coat pistons the first thing you do is sand blast the crowns to give the coating tooth to adhere to. Small nicks won’t make your piston unbalanced or shatter under load. As long as you aren’t sitting there watching the wire brush dig a channel into your piston you’ll be fine.

Ring lands on the other hand need to be protected. And watch out that you don’t get and stray wire shed from the wire brush or wheel stuck between the bore and the piston. They will work their way down to the rings and make trouble.
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