[327amc]

86' 305 sbc. Not sure on the history of the motor, other than it was never inconvenienced by pesky oil changes.


Anyways, what causes these 'dings' in the piston surface?

Piston #1 is the worst (pictured) #7 has a half dozen of these 'dings' and #2 and #6 have a small amount aswell.

And the corresponding chambers have the same 'dings' aswell.
All 'dings' are in the upper areas of the pistons only. None in the lower areas.

 

[64nailhead]

Debris in cylinder at some point. Looks like it enjoyed being for for a minute or two :0

 

[cozwurth]

I'm sure it sounded nice while it happened, too. Whatever it was is probably in the cat converter or muffler of whatever car it was in at the time.

 

[johnsongrass1]

Did it eat a bag of BB's?

 

[327amc]

Who knows. I think a crackhead built it. I also found a 1/4-20 bolt laying in between a couple of rockers on the drivers head.
On the plus side, all the sludge held it in place. It wasnt goin no where.

 

[BogiesAnnex1]

Never seen anything quite like it. It looks like steam pockets exploding in thick or carburized oil. I’d say like water drops turned to steam exploding in well cooked STP.

What I do see in the corners of valve reliefs is a goo that looks like a mixture of oil and water or coolant. Can you check that out and try to describe how it behaves when disturbed with a sharp tool?

Bogie

 

[cerial]

I am guessing head gasket (fix in a can) material and oil/water/hardening stuff trying to be compressed.

 

[ericnova72]

Seen it before, even on better maintained stuff....something foreign and hard got in there, whether it be loose carb throttle plate or baseplarte fastener or something dropped in the intake by accident..
Dents in the cylinder head say it was a hard material,not aluminum or brass, most likely steel. I've had pistons lift ring land chunks out and that won't dent the head unless ring chunks are also involved.

 

[st3gamefarm]

Yes, some foreign material bouncing around in there. I had an Oldsmobile come in the shop one time with an awful racket, which would swap places. With use of a long 3/8 extension and my ear, I discerned that it was in the top. Pulled the heads, and found a small dowel looking piece of steel. Mabe 1/16" x 1/2" on top of one of the pistons. How it could swap from left bank to right bank, is beyond me, but it did. Put it back together and it's still going strong.

 

[ericnova72]

Yes, some foreign material bouncing around in there. I had an Oldsmobile come in the shop one time with an awful racket, which would swap places. With use of a long 3/8 extension and my ear, I discerned that it was in the top. Pulled the heads, and found a small dowel looking piece of steel. Mabe 1/16" x 1/2" on top of one of the pistons. How it could swap from left bank to right bank, is beyond me, but it did. Put it back together and it's still going strong.

I've personally seen damage from one cy;inder end up in five different cylinders before.

The beyond hurricane-like dynamics in the intake tract and the fact that the intake valve typically opens before TDC lets chunks get out to be drawn into other cylinders.

Jon Kasse, the big Ford guru, has a couple video's on YouTube that are quite enlightening....he has a couple of clear tube runners and clear plenum box on a tunnel ram, alomg with a port hole big enough to put your finger in, so he could see and feel flow dynamics in a running engine during dyno pulls.
He about gets the end of one finger tore off with it in the port during high rpm, it gets thrashed by airflow in both directions in the intake port.

 

[PHWOARchild]

I know... whoever did head work on it left blast media trapped somewhere then assembled the heads.