So, what are the dimples on the valves? FOD maybe?

probably from when his pistons commited suicide

But aluminum putting marks like that on a valve face? I guess it it was moving fast enough.

And at that temperature

Jesus! Yeah post logs so we can see what was the true cause here

Head shop marking

I would assume these dots cause heat spots. Didn't they have edding markers?

Marking them for what? Those valves are rock hard - they'd have to really strike them to get those marks.

Marking them in order to know which goes where - I believe this is not the first head it been done to.

Could it be responsible for hot spots and the pre ignition that melted the pistons ?

Thanks
Elior

No. You are

Lol, fire your tuner.

I tuned it and there were no abnormal signs while tuning, could be the few 20psi peaks did the kill.

I'll try better next time - in a week or two.

Those pistons are eroded, that doesnt just happen with a few spikes. You were consistently detonating. You need to make or get a set of detcans. There most deff was abnormal signs with the way your pistons look, you just didn't pick up on them.

Take pictures of that motor too.

I have heard of dimples on combustion chamber surfaces, to reduce detonation.

Just be sure to set your base timing at idle before you drive anywhere next time.

Never forget Singh Grooves.

Severe detonation can melt a piston nearly instantly. I've had pistons on a two-stroke go from new to totally melted down in less than a 1/2 lap of a track. Mild detonation can also slowly erode the softer metals. But that to me looks pretty catastrophic (instant).

On second look, those are clearly marks from the engine builder. 6 marks on intake/exhaust valve, 7 marks on another set. That is a stupid way to mark them, just use a marker pen. Yes, those could initiate detonation due to a point source of heat forming, but they aren't the cause. The cause is you thinking you can run 20psi without proper tuning and fuel.

-removed my rude comment, unnecessary-

As I said, fuel was 11.5-12 all the time (could be the sensor is off, it is my ls4.2 spartan running for 7 years now).
The timing map is @ less then 10deg from 180kpa and up (could be base timing is off I got -13deg for ecu offset).
I understand the rising edge vs falling can advance timing too.

I'll double check everything on the new build with a new digital WB and 4.9 sensor.

Thanks for the input guys :)

https://cimg3.ibsrv.net/gimg/www.mia...3ec67d3a8.jpeg


New engine to burn :)

I'm impressed, 2 weeks and you got the block re-bored and decked with new pistons? Or is that just new pistons only? No matter, I can barely change spark plugs in 2 weeks.