Piston diagnosis

[Frank Odenthal]

What is causing the top edge of the piston rounding up that much ?
This picture is showing the No1 piston and effect is only present at the exhaust side.
It‘s from my 1966 383,approximativ 125,000 miles.

 

[SIPLOWGUY]

Is the piston loose at the wrist pin?

 

[CBODY67]

LOTS of carbon on that piston crown. Was the carburetor running rich all of the time? As there is no clean spots near the edges, looks like the oil rings were still working pretty good. Otherwise, the outer edges would be "washed' clean.

Any performance issues with that engine? Just curious.

CBODY67

 

[Big_John]

What is causing the top edge of the piston rounding up that much ?
This picture is showing the No1 piston and effect is only present at the exhaust side.
It‘s from my 1966 383,approximativ 125,000 miles.

View attachment 749653

Detonation will do that. Detonation tends to damage the edge of the piston while pre-ignition damages the center.

Here's a pic showing more severe damage.

 

[Frank Odenthal]

LOTS of carbon on that piston crown. Was the carburetor running rich all of the time? As there is no clean spots near the edges, looks like the oil rings were still working pretty good. Otherwise, the outer edges would be "washed' clean.

Any performance issues with that engine? Just curious.

CBODY67

I‘ve already scraped off the carbon from the piston and cleaned a Bit. There was much more Carbon on it.
Yes, Engine was running to rich on some cylinders and were sucking oil through valve guides.
No.6 had a broken compression Ring and spark plug become fould after short Time.
Poor performance and valve Train noise on Right Bank was reason to pull the heads and after this engine was pulled to check the Rest.

Yes, Lots of Performance loss on that engine.
Frank.

 

[MONC440]

Detonation will do that. Detonation tends to damage the edge of the piston while pre-ignition damages the center.

Agreed! Detonation will happen the most in hot spots in the cylinder so that being on the exhaust side makes sense.