team2zon

iTrader: (8)

Is the top of the piston supposed to turn a brownish black after its broken in? or is it supposed to stay shiny silver?

Also, what does pitting look like? I heard this happens from to much compression.

thanks

xDaRReLLx87

That is perfectly normal What do you mean by pitting?

lowblktaco

iTrader: (21)

Pitting is not normal, carbon colored coating is normal as well.

Briguy

iTrader: (125)

Pitting is little pin holes starting to develop in the piston . This can happen from too much compression , not enough shims or longer glow plug .

zixxer

iTrader: (61)

if the top of the piston looks like its been sandblasted ...its been run to lean....carbon build up is always normal

Dalepad

I have heard that running too hot of a plug can also do that.

Briguy

iTrader: (125)

I know with regular gas engines a too hot plug will do it . Not sure about with glow plugs .

AreCee

iTrader: (1)

Pitting is like pinging in a 1:1 engine. It's mostly from pre-detonation of the fuel/air mix. This could happen when the engine is overheated, using a hot plug (similar to advancing the timing), running too lean or not shimmed properly.

Another effect of pre-detonation is excessive wear on the conrod and shaft journal bushings.

asw7576

Pitting is surface deformation on the piston head and underneath the button head. They become sand blasted due to overheating, perhaps due too high percentage on nitro % or running too lean.

I've got this pitting problem 3 times......

To reduce pitting : polish the piston head and button head until they become so shiny. I find this trick work very well to minimize pitting. I use dremel and round wool type tip, especially meant for polishing jewerly.

Don't polish inside the sleeve or inside the engine wall where the sleeve is seated.

Briguy

iTrader: (125)

He asked what it looks like . Not what it is , what it looks like . So not sure why you are laughing at my post .

asw7576

Pitting in this conversation means the surface condition of a piston head :
Look like having a carbon build up is normal.
Look like it has been sand blasted, it's not normal.

Briguy

iTrader: (125)

Ya , I know . Where did I say pitting is normal ?

xDaRReLLx87

TY for explaining the pitting term for me

Briguy

iTrader: (125)

Instead of polishing you should fix the problem why it is happening . That is just putting a band aid on it instead of taking care of it .

xDaRReLLx87

wouldn't using a fuel such as 30% heli fuel with more oil would lubricate the piston enough to minimize pitting? Back when I used 20% I would mix castor oil in it