I have taken the head off my engine and the next thing I want to do is clean the pistons while the head is getting rebuilt. I have also heard a lot of ways to clean them like alcohol, simple green and coke but what's the best way? My second question is the exhaust pipe I want to get all the carbon out of the system but I am not really sure what to do or use. Thanks
IMO, If you are just removing head, Do not use any of products you mentioned, you do not want these products in crankcase, clylinder wall, rings. Put each cyl on TDC and clean w/wire wheel carefully, do not damage pistons, cast pistons easily damaged, tape off other cylinders, you do not want dirt, debris in cylinders. Would not worry about exhaust IMO, unless it's horribly blocked, you could remover header and sand blast inside, after typing/thinking, would not clean pistons, check ridge at top of cylinder, if it's big enough to feel step, probably should torn down. Sometimes when freshened heads are put on well used engine, the blow by increases, you end up pulling engine anyway. Just my thoughts from my experiences, the engine experts will answer your questions better than me, Good Luck w/ your project.
What is the engine? Is it in the car? How many miles on the shortblock? How 'bad' is the build-up? As wicarnut asks, and for the same reason, how much ridge? The problem with 'cleaning' the tops is that you will have debris getting into the annular space above the top ring. I 'spose you could rely on a vacuum to suck up the crud as you scrape but you will never get it all, and the problem with the loose crud is that carbon is very hard and you can end up with cylinder wall scratches. If this is an old, tired, shortblock then why worry....but then why re-do the heads? .
It's all been said already so I leave all of you with this. Never start the engine to begin with. It'll stay as shiny as the first day it was put together.
Too late now but an old tried an true method is to pour Marvel Mystery Oil or automatic transmission fluid down the carburetor while revving the engine to about 3000 rpm. You have to do this outside in a wide open area prefereably on a windy day because it will produce a lot of white smoke.
Might be out of date this day and age.. Back in the day, we carefully used a scraper to remove the carbon, but leave a ring about a 1/4 inch around the edge, so as you don't cause the piston to lose it's seal..
So that 1/4'' ring of carbon around the perimeter of the piston is a seal to the cylinder wall. Humm....interesting.
There is no way to get all of the small carbon bits that fall down between the piston and top ring but when in doubt, with the piston down in the bore about an inch put a coating of grease around the bore then bring the piston up to TDC. Now when you scrape the piston top the crap will be stuck in the grease. Clean up the grease and blow out the gap with compressed air. As far as getting carbon out of the exhaust pipe the only way is replace the pipe. If your engine has that much build up a little carbon dust probably won't make much difference.
Wait 'til you put it back together and then set your idle a little fast and dribble water down your carb. It will make a nice little pile of carbon just behind the tail pipe. Totally old school but it works.
http://www.austin7.org/Technical Advice/Engine De-coke/ Old civilian reference to the sealing function of carbon near the piston's edge. (Not saying I'm buying it) http://www.mg-cars.org.uk/imgytr/pdf/pmmc1058.pdf And a clever way to maintain it during a "decoke."
As mentioned in post 2, do not allow any chemicals on the walls of the cylinders as it will wash off the glaze and the rings will be hard pressed to seal again. Bring each piston to TDC and scrape and soft wire brush the tops, blow air to clean when you're done. Carb cleaner and brake cleaner are not your friend in this instance.
Worked well in an era where "Shop-Vac" was a non existent thing. But I'm referring to cleaning as this thread asking. What it's referring to is carbon acting as a seal. But how when the rings have not even reached that destination (carbon) to so. By that point the rings will have or have not done their job to insure proper compression.
A little carbon the exhaust will keep the pipes cooler. Guys with chrome hedders grease the inside of the hedders so it will turn to carbon and help the chrome from turning blue.
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