355 Piston DeCarbonization

My take on this would be to leave it alone. Trying to take carbon off of the top of the psiton with it still in the cylinder is bound to drop stuff down between the piston and the cylinder wall....

If you really wanted to clean them then I'd suggest pulling them from the bore and doing it correctly.

 

If the carbon build up is so bad that it is a problem there is more than likely issues that will require piston removal for correction. The ideal situation is to pull the pistons, disassemble from the rod and clean by hand. If you just want them to look good and clean prior to putting the heads back on you can carefully use a little scotchbrite and carb cleaner and scrub the tops by hand while the piston is at TDC. Use compressed air and be sure to clean the bore out when done. Many will scoff at this method but a little care and common sense go a long way and just be sure to have the bore and the area around the piston crown clean before installing the heads. Use your best judgment but this can easily be done with good results, just be sure you don't wash debris down the bore.

Good luck.

 

How about some plain old acetone and a rag?

What do you ya think James? Or is the scotchbrite pad a must?

 

I did the same with a 928 engine (aluminum block, no sleeves). I covered the area around each piston with towels to keep the green stuff from getting into everything.

I went one step further and soaked each piston top with parts cleaner. Most will say this is about the dumbest thing you can do since some of the fluid will eventually drip past the rings & wash off the cylinder walls. I did it anyway since I didn't know any better (this was a while ago on my car). Once everything was cleaned up I did soak each piston top with oil and moved the engine up and down quite a bit by hand to re-oil the cylinders. 5+ years later my motor is still going strong making over double the original horsepower.

Be careful & take your time. After doing some scrubbing I would rotate the engine to drop the piston I was working on down a bit, most of the "gunk" would be stuck to the oil film on the cylinder wall. I would do this over and over while scrubbing to avoid buildup on top of the ring.

 

A like the scothcbrite for giving a little abrasion to knock down the stuff, but it ain't rocket science. A rag is fine you just need to put more elbow grease in the job. I think the most important issue, as in all service procedures, is don't be messy.

 

Okay, rag or Scotchbrite and carb-cleaner. Piston at TDC, use care not to damage anything. After you're done and EVERY TRACE of carb-cleaner (explosive) has evaporated, use the shop-vacuum to clean the piston/cylinder gap area to get the debris out. I prefer not to blow things out with air, especially the abrasive grit from the Scotchbrite.

Finally put a small amount of oil around the top ring before the head goes back on.

You can't be TOO CLEAN.