I bought a used set of pistons and they have some carbon on the top of them. Should I clean them? How would you clean them? Also I don't have a part number on them. I spoke with the manufacturer to try and get some info on the rings. He just said measure the lands and it will either be close to 1/16 or .043" or 3/16 or 3 mm and that will tell me what rings to get. He also said they are file fit rings. What exactly is the process for file fitting? Or what kind of gap am I looking for? It will be a supercharged engine I have never set up some used pistons before - any pointers or help would be appreciated. Hey Hog Mtn Dave - Can I come over and use your head CC measuring tool to measure the dish? I said head and tool and measure in the same sentence. Thanks CHUCK
Yes you should clean them. I've never had to clean used pistons before but I'd think anything that doesn't scratch the piston deeply or damage it chemically should be fine. Carbon in the combustion chamber can lead to hot-spots and pre-ignition or pinging. File fitting rings involves filing the ends of the rings to get the proper gap when the ring is in the bore. Put the ring in the bore and square it up by pushing it in with a piston top. Then using a feeler gauge, measure the gap. File to get the proper gap for your application. The gap will be dependent on the ring manufacturer specs for the specific engine and aspiration. That's all I can offer you based upon my limited knowledge. Someone else can probably give you more specifics.
I'm thinkin' oven cleaner if the carbon is "wet". If it's dry ya could mask off the ring lands and bead blast the tops. But I'm interested in hearing any other ideas.
Most piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches. For the 2nd compression ring, the standard end gap recommendation for most stock engines is typically .005 in. x the bore diameter. So for a 4 inch bore, the minimum end gap on the 2nd ring would be .020 inches. For a modified street performance engine that generates more horsepower and heat, the end gap should be opened up a bit to compensate for increased thermal expansion. The recommendation would be a minimum top compression piston ring end gap of.0045 to .005 inches times the bore diameter. For a 4 inch bore, the ring end gap on the top ring should be increased to .018 to .020 inches. For the 2nd compression ring on a modified street performance engine, the recommendation is typically open up the end gap to .0055 inches times the bore diameter. For a 4 inch bore, the 2nd ring would be gapped to .022 inches. For a nitrous or blown racing engine, the top ring end gap sould be opened up to as much as .006 or .007 inches times the bore diameter. Now we're looking at a 2nd ring end gap of .024 to .028 inches in an engine with 4 inch bores. For the 2nd ring on a nitrous or blown motor, the recommended ring end gap is even wider: .0063 to .0073 inchestimes the bore ( or 0.025 to 0.029 inches with a 4 inch bore). The recommended ring end gap for oil rings regardless of the engine application is typically .015 inches. Some racers believe that opening up the 2nd end gap even more (say an additional 10%) can improve overall ring sealing by allowing trapped gases to escape before they blow past the top ring and cause ring flutter at high rpm (say above 5000 to 6000 rpm). NOTE: These recommendations are rules of thumb only. Always follow the end gap specifications recommended by the piston ring supplier or engine manufacturer.
Water actually works pretty well on piston tops...it takes time & elbow grease, but it does the least amount of damage. A soft wire wheel would be another choice, but keep it away from the skirts. So far as gaps are concerned....what engine, what bore, what boost? The stuff listed by r8odecay is pretty close for an average small block or "regular" big block. Bore sizes that are very small or very large compared to the norm may vary a bit depending on use. The big thing is to keep the ring ends square. You can do this with a hand file, but if you've never really done it before you might want to get one of the ring filers sold by Summit or whoever- makes life easier. Pick rings that are .005 larger than your finished bore size- you'll see rings measured in .005, .035, .065, etc.
Are you SURE you have to get file to fit rings? If they are a super thin low tension plasma moly ring, they are most likely file fit, but other than that, you ought to be able to get some pre-sized rings. Hell, it IS a small block Chevvie...can't you just run down to Wal-Mart and get a set of rings??? (ha ha!) File to fit is no big deal if you can work a feeler gauge and ring file. My file is a Summit brand clamp it in a vise deal. Works great..39 bucks or so. There is a trick to it though... Good luck, -Abone.
Here is what mine looks like... The trick it to practice on an old set of rings to get a feel for how many turns of the handle it takes to remove how much material. Once your gap is too big....well..you know... -Abone.
Like the others mentioned,I would highly reccomend buying a ring filer.It's really a challenge to maintain a high degree of accuracy with a hand held file.
Yes, plain old water works well. We use it a lot on used diesel pistons. Let them soak a bit and most of the carbon will come off with a putty knife and a final touch up with some scotchbrite. If you do decide to use a bench grinder, be careful of a hard wire wheel as it will embed steel into the aluminum piston top and will cause hot spots.
I have had really good luck with soaking the tops of the pistons in a little bit of Castrol SuperClean. Get an old coffee can or tub-o-****er and put just enough to cover to the top ring land. It has always worked well for me and the crud just wipes of with little to no h***le. As for the ring gap just go by what you are building and manufacturing specs and DO go buy a ring filer. Since I bought mine I have used it quite a bit.
If you gap the rings with a hand file, the trick is to clamp the file (fine cut and not too thick) in a vise, hold both ends of the ring between your thumbs and index fingers and work both ends of the ring against the file at the same time. Cut on the push, release pressure on the pull. Gently debur the outside corner with a stone. It's not too difficult to get a good result. I've never had a ring filer but I'd probably use one if I did.
I soak my valves, pistons and what-not overnight in 'Top Engine Cleaner' to remove carbon. It's available at every GM dealer in the world and it works (it is what it is designed to do). Get the plain can of it, not the aerosol
At the Porsche shop I used to work in we used Easy Off oven cleaner to get the carbon off the pistons. Worked pretty well
Hell I think I got some in some crackerjacks last week. they were call belly ****on rings though. J/K Sounds like yer getting ready to build another blower motor. Shouldn't we fire up your first one...........first?
Carb cleaner works really good. If it's real stubborn I'll use a soft br*** wire bruse along with the carb cleaner. I don't know if this is the correct way or the best way but I know it works.
I put a set of pistons in the dishwasher once. Turned the white plastic inside of the washer a nice Dove Gray... Wife said,,, well actually she didn't say anything, just gave me that "look". The washer faded back to white, in about three years...
X2 for doing it the hard way. Then I tried some good ol' oven cleaner and scotchbrite (and rubber gloves). A better method. -bill
Oven cleaner will work...but keep it off the skirts, & especially the ring lands. It can damage the land side surfaces (which are basically a lapped sealing surface) & cause problems. Not saying it will....but it can...seen it happen.
It says right on the side of EasyOff cans, do not use on aluminum. Likewise Castrol Purple cleaner says to use with caution on aluminum (but I use it for that, it usually just discolors it). I use the 4" Scotchbrite "red" wheel in a die grinder, it won't hurt anything.
I use HYDROSEAL, a decarbonizer; just soak overnight and wash off with warm water. Made by Gunk. I never use a wire brush or wheel on pistons; they will leave scratches. I will use a paint brush to get into the ring lands. Kerosene also works but not as good as HYDROSEAL. Nice, shiney, new appearing aluminum pistons! BUTCH.
Paint stripper or the spray on Permatex spray on decal remover work the nuts with only a paper towel to wipe the carbon off with only couple of applications. Another option if you don't want to use methylene chloride (most paint strippers) is to make your way to your local Mercury Marine dealer. Go to the parts counter and ask for a spray can of "Power Tune". Its made to free up stuck rings in the older Mercs that did not use keystone type piston rings. It works a charm on the carbon deposits without much scubbing. In any case you want to minimize any marking or scratching of any surface on the piston. Once all the **** is off the slugs you can mask off the ring lands and skirts and beadblast the surface with a fine gl*** shot/beads. -Bigchief.
Thanks for all the replies - Sounds like I need some decarbonizer to soak them in. I'll probably go the non abr***ive route, they are not really covered up. I measured the lands last night, they are 1/16, 1/16, 3/16 lands. I appreciate the gap information, I will follow the manufacturers instructions. Jeff - the guy at Manley told me to get file to fit rings. So I guess they are. You are right any old chevy rings would probably work. I spoke with Hog Mtn Dave and they have a ring filer. Probably go over there and get some help. And yes Dave - I probably should fire up the other motor first, but I am sort of shooting to stick this inthe 46 for run what ya brung This way I might have something for Pauly.
i wouldn't go less than .020 on top rings. Get a name off the piston and check with manufacturer as some like KB require a lot. You will get recommendations with the rings also. I file with a points file, inward strokes.
File fit rings should come with gapping instructions based on your intended usage. Blower / Nitrous / Alcohol etc. The use of file fit rings is based on your bore size, not the piston type. Check your piston/cylinder wall clearance. Old forged pistons had a low silicone content so they tended to grow more with heat, and therefore can be run with up to a .010 clearance, with minimum of .003. Newer forged units with higher silicone content require less clearance. Around .0025-.0045. Cast pistons don't grow nearly as much and require about .0015-.003. Don't forget to clean your ring grooves! Take an old ring and break it in half, and run it through the grooves, or rent the tool. Ring side clearance should be checked for about .001-.003. These are all typical clearances. Check manuals for your specific application.
Would love to make it. Never been, but I've heard a lot about it. Could you PM me some details? Thanks - Mike
Thanks Josh--I feel a whole lot better now about my shop full of half-finished junk! I don't know what the RPM rating is, but you can get a br*** wire wheel at the hardward store. Br***, being softer than aluminum, shouldn't leave any scratches in the pistons. I've got one, but never put it on a grinder--just a hand drill. -Brad
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