<VV> Cleaning Piston Crowns

corvairduval at cox.net corvairduval at cox.net
Thu Apr 3 12:27:44 EDT 2014

If we are speaking of cleaning while the engine is still operational, use
the water trick. Just google water decarbonizing engine. This is a good
trick to remember to do before tearing an engine down, as it gets the
combustion chambers cleaner than not doing it.

And of course there is (was) GM Top Engine Cleaner.  Follow directions on

I'm sure there are a number of other expensive snake oil treatments to pour
into the engine while it is running. But water works and is cheap!

As Paul says, keep the engine running, or it may lock up against a carbon
chunk. Besides, pouring anything into a stopped engine will result in
hydrolock. To cure hydrolock, one must remove the spark plugs and bump the
engine over. If it hydrolocks while running... expect bent parts.

Original email:
From: Paul Fox paulvair at yahoo.com
Date: Thu, 3 Apr 2014 05:10:47 -0700 (PDT)
To: corvairduval at cox.net, virtualvairs at corvair.org
Subject: Re: <VV> Cleaning Piston Crowns

I'd be careful doing that any other way than driving it hard. The reason
is, if it comes off all at the once it falls to the bottom of the
chamber and can jam the pistons so you can't turn the engine. I've had this
happen more than once. When it happened I thought something was broken
inside the engine. after I pulled the heads it was just carbon that had
collected in the quench area of the chamber. 
On Wednesday, April 2, 2014 1:13 PM, "corvairduval at cox.net"
<corvairduval at cox.net> wrote:
I don't know a best way, but...

I strongly recommend you pull the pistons out of the engine (by removing
rods from engine) to examine them closely for cracks.

If you find none, you can put them right back in, just keep the same
bearing shells in the same locations.

The OEM pistons crack a lot. Especially around the oil ring groove. This
causes the top of the piston to come off.

Frank DuVal

Original email:
From: Paul Michalczyk paulm at tdl.com
Date: Wed, 2 Apr 2014 10:01:34 -0700
To: virtualvairs at corvair.org
Subject: <VV> Cleaning Piston Crowns

I'm preparing a spare engine for my 65 140 Corsa and don't want to tear 
things down further than I need to. What's the best way to remove carbon 
buildup on the piston tops without removing the pistons and rods from 
the engine?

Paul Michalczyk

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