cheetah chrome

Here is a summary of my removing carbon from 951 piston domes experience. My goal was to remove the carbon from the piston domes while minimizing the risk of carbon deposits being left behind and scoring cylinder walls. I followed the below procedure to the note and it was surprisingly easy. Thanks to everyone that I was able to beg/borrow/steal info from!!!

Coarse Cleaning:
- Clean pistons in pairs: Set pistons 1&4/2&3 a third of the way down in cylinder bores.
- Fill cylinders w/ Mopar combustion chamber cleaner until the full dome is submersed in the cleaner.
- Let domes soak over night
- Wad up paper towels and soak up the bulk of the cleaner that is in the cylinders. Once the bulk of the cleaner is removed wipe the domes w/ fresh paper towels.....continue to wipe until domes are dry and all loose carbon (which is the consistency of sludge) is removed. I used nitrile gloves for this step and in just this step alone I remove 90% of the carbon that was on my pistons.
- Apply a liberal coat of Vaseline to the edge of the domes/cylinder walls and rotate the pistons that you are working on down a 1/2". The Vaseline will help "stick" any carbon sludge that has settled down at the rings to the cylinder walls. Using a clean paper towel wipe clean the cylinder walls. Add more Vaseline and repeat...it took me a couple of times to get the gunk out of there but now I can crank through a complete rotation w/o anything showing up on the walls.

Fine Cleaning:
- Again clean in pairs: Set the pistons 1&4/2&3 down so the top of the dome is at the carbon ring on the cylinder wall at top of the cylinder (the “carbon ring” is roughly a 1/3rd of an inch down from the top of the cylinder…where the top of the ring sits when the piston is fired….this will protect the mating surface of the cylinder getting accidentally touched w/ the Scotch Brite pad and the cylinder wall because it is above where the ring will ever contact it).
- Apply a liberal coat of Vaseline to the edge of the domes/cylinder walls that you are working. The Vaseline will help minimize any carbon dust/chunks getting down to the rings.
- Use a Scotch Brite pad to clean any left over carbon from the coarse cleaning.
- Rotate the pistons that you are working on down a 1/2". Using a clean paper towel wipe clean the cylinder walls. Add more Vaseline and repeat until all domes are clean and cylinder walls are clean through an entire rotation.

Before Reassembly:
- Spray down each cylinder w/ Mopar combustion chamber cleaner being sure to spray the edge of the domes/cylinder walls to remove any remaining Vaseline. Hand rotate engine one more time just to be sure you are as clean as can be. Liberally coat cylinder walls w/ assembly lube, reset piston 1 to TDC and you’re done.

*For my rebuild I am also doing the pan gasket so I will dip tank the pan itself. If someone wasn’t they could do this as an added safety measure: once they have the motor fully assembled and filled motor oil, run the “initial oil” for a short period of time and then do a change to ensure any combustion chamber cleaner that got past the rings is not in their oil supply…I will probably do this regardless of replacing pan gasket.

Thanks again everyone!

UK952

I used grease in the bores rather than vasalene and a soft nylon brush in a dremel,
Tony

Laust Pedersen

And after this somewhat risky clean-up effort, what prevents the carbon from coming right back after a few hundred miles?

Laust

UK952

took 170k toget that bad in the first place - and it wasnt that bad
Tony

Fishey

DieGrinder and Fine Wire Cup 2" + Brake Clean

Turn to TDC and go to town works better then anything else.

cheetah chrome

I think that the carbon on my domes was pretty characteristic of a 100k mile engine. My PO had autothority software/jetted banjo bolt...which I've read were pretty rich down low and pretty lean up top so that maybe a contributor to my build up. At the build up's thickest point(s) there was some "scaling"...if you would run along it w/ your finger nail you could break free some of the carbon deposits. For my own piece of mind and trying to minimize the chance of detonation from carbon hotspots and the chance of getting scored cylinder walls from a loose piece of carbon breaking free....w/o pulling the pistons (unfortunately, financially that is not an option at this time)...I did it this way. The Mopar cleaner work great...after a 24hr soak you literally wipe off 90% of the carbon that was on the pistons.

Fishey, using a rotary tool at TDC, even w/ a soft wheel...do you let it hit the wheel hit the mating surface of the cylinder?

Albeit the carbon build up is unavoidable...I'm hoping to minimize it w/ getting my AFRs right w/ hardware and software changes going in at reassembly. Laust, "in block" method aside, on refreshing a motor would you reinstall carbon coated pistons back into the block?

Fishey

When the piston you are cleaning is TDC there is no way to hit the cylinderwall with the rotary tool. Just remember to crank over the motor to clean each cylinder.. Also cleaning the head/block mating surface this way is also very effective...