Piston problems
 

I have a .28 engine and I had rebuilt it recently to get some carbon off the piston and then I ran it for it a few weeks. Then it sat for about 3 weeks with after run oil in it. Today I ran it and afterwards I then took the head button off to find that the piston and head where very rough as it had been it had been eating itself apart. I was wondering if this could be corrosion or something els? And does anybody think this problem can be fixed?

Thanks for your help
Ajkracing

RE: Piston problems
 

R U sure the piston and glow plug weren't contacting?

RE: Piston problems
 

What % fuel are you using, head shims, and what heat range of glow plug? Sounds like detonation to me. Try adding a shim and getting a colder plug, or just lower your nitro %.

RE: Piston problems
 

It's probably pinging (detonation)
It happens when you're running too lean, too high of a compression (add shims like mentioned before) or too high of a nitro level.
What happens is the engine heats up so much and it ignites the mixture on the upward stroke instead of the downward, causing damage

Here is my head from a OS CVR which has detonation marks on it, the piston head has similar marks as well
http://i26.photobucket.com/albums/c1...3/IMG_0230.jpg

RE: Piston problems
 

yep that looks about right I am running 20% with a o.s 8 plug. I will try to put a shim on the head.

RE: Piston problems
 

What brand fuel and blend are you running? High oil content in fuel can cause a person to over lean. What engine is it? OS plugs are a short plug and most engines other then OS take a standard long plug.

RE: Piston problems
 

Its wildcat 20% nitro 20% oil. I know it is way to much oil but its the only fuel my shop had. The engine is a sh.28

RE: Piston problems
 

High oil content can't cause overleaning because the engine only sees how much nitro/methanol is being fed into it and that's the only think the needle valve adjusts for. The oil is only along for the ride. If you change oil content then you have to retune to account for the change but the end result is still to have the same amount of nitro/methanol going into the engine. All that 20% oil is likely to do is make the engine last longer.