Detonation damage?

[Captain75]

Hello friends!
When giving my 2.7 Looper some winter maintenance, I discovered some alarming marks on #2 piston and head squish band. Picture quality isn't top notch, but think you get the idea...
Is this due to a lean contition? I am running 110psi comp, good fuel. Pistons in port bank are all black, but the stbd ones are showing some wash...
My intention was to give the heads an additional shave, but I feel that I need to sort this out first!

Btw I´m running midbores with an airbox w/o baffle. Mains drilled to .076(cyl 1, 2, 3, 4) and .078(cyl 5 &6)
106 Pullovers, 26mids, 48idles.
Timimng is set to 18deg, last checked 2 years ago.
Detonation damage on the edge of piston?

Head damage in the squish band.

Port pistons, all black...

Stbd pistons showing some wash... The one on right is #5(drilled jet 0.078")

What do you guys think, is the mixture too lean?
Will an additional head shave (~0.020 - 0.040") require a switch to an non-gutted airbox, together with something like 68D´s (stock is 62D)?

Looking forward to your thoughts on the subject!

Best regards!
//Anders

[racer]

Something went thru the engine.

[Captain75]

Racer, glad you replied! Can you tell me anything about the piston colour? The motor was driven really hard before I
I want to shave another .020" - .040" off the heads, just need to have some pointers in order to create me a baseline concerning jetting.
Btw heads were shaved 0.039" two years ago

[Snotrekie]

motor ate something take it apart.

[flabum1017]

Something went thru the engine.

Possible broken reed, broken ring or chipped off a piece of cylinder by ports. Any scoring in the cylinder walls?

[Captain75]

Possible broken reed, broken ring or chipped off a piece of cylinder by ports. Any scoring in the cylinder walls?

No scoring in the walls. Just some damage to the piston edge, something I think I managed to fix by use of some 320grit paper. Do you have any ideas concerning piston colour vs jetting?
I was hoping i could give the motor one more season before rebuild, and the plan is to raise compression a bit by a head shave and also raise the primary compression which is described in another thread.
What are your opinions on the idea of giving the upper, compression part of the bores a run with a 320grit ballhone when the motor is still assembled? I think you should be able to do this if you cover the ports by laying a "lid" on top of the piston!?
//Anders

[Capt.Insane-o]

What are your opinions on the idea of giving the upper, compression part of the bores a run with a 320grit ballhone when the motor is still assembled? I think you should be able to do this if you cover the ports by laying a "lid" on top of the piston!?
//Anders

Umm.....no.

[outasite]

Umm,,,,,no. You already have worn rings.They will not reseat,that would only burn up what's left in a very short time.

[Snotrekie]

Take it apart

[baja200merk]

Slide that piston out, block off the exhaust and crank case. Hone it, install new rings and run it.

[Captain75]

Thanks for your replies! Any thoughts on piston colour/wash?