What happened here - pics of eroded hole in piston... (1 Viewer)

[erics]

Doing post mortem on a 2F that died... think this is the culprit?

Two questions:
1) what would cause this to erode/burn away like this?
2) I notice the "49" marked on top of each piston is different than "46" which I find in another engine I opened up... does this indicate that the dead engine had been rebuilt/bored out with oversize pistons and they possibly used poor quality parts leading to the failure (and others starting to show degradation around the edges as well)?

 

[brian]

pre ignition

 

[erics]

Google tells me a burnt valve or high carbon buildup are likely causes of pre ignition - what's the best guess here (ie most likely in a 2F)?

Can anyone tell me about the 49 marking on the cylinder tops?

 

[brian]

is it just crud? but it looks like the other two pistons are also showing signs of erosion also.

 

[pb4ugo]

Google tells me a burnt valve or high carbon buildup are likely causes of pre ignition - what's the best guess here (ie most likely in a 2F)?

Can anyone tell me about the 49 marking on the cylinder tops?

Could be to much timing, poor or low octane gas, a lean condition creating hot spots, etc. There's certainly no carbon on those pistons.

 

[Skreddy]

How does the exhaust valve look for that cylinder?

 

[erics]

a couple pics of the valves in question - I don't know what I'm looking for...

 

[Skreddy]

What’s the backstory on the engine? Those Valves look too good for that head….

 

[Skreddy]

I meant…. Those valves/that head look too good for that engine. Combustion chamber looks clean and crisp but cylinders and piston look worn out.

 

[erics]

Engine was in a basically one-owner 150k++ truck that we bought from that owner's widow a number of years after his passing after being connected with her by one of the tech guru shop owners on here. Said shop owner isnt aware of any major rebuild or head replacement kind of work having been done, but that doesnt mean something wasnt done without his knowledge/involvement. A couple folks have told me the piston markings I asked about above probably don't indicate anything either - but interested in any opinions on that.

Current plan is to have machine shop check head out and if good pull pistons to verify whether cylinders workable. If so then reassemble with new pistons and try to run it (albeit in a different rig as there's a 1HZ now installed in its place).

 

[pb4ugo]

No much carbon there either. You can poor acetone in the chambers and see if it leaks past the valves.