Re: How bad do my pistons look?

Posted by Duncan Michael On 2019/12/18 21:41:43

In the photo of cyl #2 (marked in red) , a small piece of the piston is missing, or burned away. With the exception of cyl #5, all are using oil. The pitting in the cylinders is the result of long term storage without lubricating (aka pickling). When rust forms in the bore, and the engine is rotated, the rings will scrape the oxidation loose , where it will lodge between the piston ring and the ring land. When the piston changes direction, it rocks. The particles that have accumulated will cause the ring to stick, resulting in lost cylinder sealing. The 2nd ring's primary function is oil control. If the cylinder is worn,or out of round, the ring cannot seal and the engine will use oil. Oil in the cylinder will cause detonation. Detonation burns pistons, breaks rings etc.

Assuming that your engine has mechanical tappets, roll the engine over and measure valve lash. Measure the intake lash when the exhaust valve starts to open, and the exhaust lash when the intake valve starts to close. Record the results. Examine the valve springs, observe the motion of the valve.
While the valve is open, look for cracks in the seat area.

Good luck.