Piston crud (1 Viewer)

[Rochfort]

Wonder has this happened after less than 500k ...?

 

[charliemeyer007]

So 300 miles. Are you seating new rings? Mixture might be a little rich, timing might be a little retarded. Could be the fuel you are burning too. Looks sooty in the exhaust pipe. Oil viscosity might be low.

 

[Rochfort]

So 300 miles. Are you seating new rings? Mixture might be a little rich, timing might be a little retarded. Could be the fuel you are burning too. Looks sooty in the exhaust pipe. Oil viscosity might be low.

..don't know what I did. Trying to track down a mystery knock.

 

[1911]

..don't know what I did. Trying to track down a mystery knock.

What is your ignition timing set at? For the elevation above sea level of Bogota, you will need a lot more advance than 7 degrees BTDC, but it's possible you could have too much if it's piston knock. Does the knock happen under load (going up a hill, or hard acceleration)?

 

[Rochfort]

What is your ignition timing set at? For the elevation above sea level of Bogota, you will need a lot more advance than 7 degrees BTDC, but it's possible you could have too much if it's piston knock. Does the knock happen under load (going up a hill, or hard acceleration)?

Yes

 

[1911]

Yes

Then it's probably piston knock (pre-ignition). The base timing is too advanced. Retard the timing a small amount at a time and drive it again, until you lose the knock under load. The goal is to have it as advanced as possible with no knock. If it's retarded too far, the exhaust will overheat. But please measure where it is now first, to see where you're starting from. A dial-back timing light will be the easiest way to do that.

 

[Rochfort]

Then it's probably piston knock (pre-ignition). The base timing is too advanced. Retard the timing a small amount at a time and drive it again, until you lose the knock under load. The goal is to have it as advanced as possible with no knock. If it's retarded too far, the exhaust will overheat. But please measure where it is now first, to see where you're starting from. A dial-back timing light will be the easiest way to do that.

OK...tjnx!
There's no preignition stutter when i shut off the engine.