Very disappointing Ken,
If you have a chance some more information would be a help.
1. You mentioned melted pistons 70K back, did you find the cause?
2. Are the notches only around the edges of the pistons (photo)?
3. Impact damage is usually fairly obvious can you be more specific.
4. Any impact damage inside the combustion chamber or on the valves?
5. Any signs of aluminium specks on the plugs or inside the combustion
6. Any history of lean running (fuel pump, carb faults etc.)?
From: firstname.lastname@example.org [mailto:email@example.com] On
Behalf Of Freese, Ken
Sent: Tuesday, January 09, 2007 10:17 AM
Subject: Pistons damaged again
I cleaned up the compression reading columns.
Saturday, I removed the head from my BJ8 to have steel valve seats
installed because of #4 exhaust valve recession and low compression. I
figured #4 was now burned enough, I should get it fixed. After putting
on the hardtop on New Years, I could hear rougher running.
Now I see that #2, 3, and 4 pistons have 1/16 to 1/8 inch notches
missing and I can see the top ring on #4. Preliminary inspection of the
notches don't show smooth melting. So, new set of problems. I figure the
1. Swallowed debris
3. Defective pistons
A - oil never filtered only changed for about the past 40000 miles due
to faulty spin on filter adapter.
B - last rebuild in 1982 and 70000 miles ago due to melted pistons
Compression 1997 Compression 2004 Compression 2007
165 130 110
155 135 90
150 145 70
150 90 70
155 130 115
175 150 145
Any thoughts on the cause until the pistons are actually out?