Back around 1998
I soaked eight 1994 Magnum 5.9L pistons in
Chevron Techron (not the current 'Plus' version of today),
Redline SI1,
Liqui-Moly Ventril Sauber (means valve cleaner in German),
Liqui-Moly Jectron,
Chrysler ATF+2,
Aircraft Paint Remover,
70% Walgreens propanol rubbing alcohol, and
Chevron Regular gasoline (not 10% ethanol back then)
The Libui-moly Ventril Sauber
http://www.liqui-moly.de/liquimoly/produktdb.nsf/id/en_1014.html?Opendocument&land=DE did the best job removing carbon from the piston tops during my soak,
and Chevron Techron did second best,
but both took over two weeks to really remove 95% of the deposits.
The Liqui-Moly products used to be in stock at
VW and BMW dealerships,
and some auto parts stores in NC at least.
They were about 50% higher priced than Chevron back then.
the expensive Yamaha 'Ring Free' is supposed to be specially designed for this job too:
http://www.yamaha-motor.com/outboard/apparel/apscitemdetail/3/145/all/1/10007/detail.aspxI also tried taking a second PCV valve and sucking the condensate water from the Ram's air conditioner system drain and injecting it into the intake through the 'test port' nipple on the driver's side of the 'Beer Barrel' factory Magnum intake.
This 'poor man's water injection' seemed to clean up carbon deposits,
reduce full throttle pinging
... but it hurt city driving MPG by about 2 MPG during the time I tried it,
which was about 3 months.
It also caused a noise that could be hear inside the pickup when the radio was off.
A $8 bottle of official
Chrysler Combustion Chamber cleaner
is a good manual de-carbonizer,
and appears to be a brown foam at least partly made of water.
I would rate Chrysler CCC as superior to Sea Foam.
Some years ago I read about a solvent for soaking aircraft engine used pistons to remove carbon deposits,
but I cannot find the link to the magazine article now. This solvent was alleged to do a very good job in less than a day of soaking.
