Piston marks?

OffRoad Cowboy · Nov 5, 2012

I got a free 5.7L small block. When I pulled the head off this is what 3 of the pistons looked like. Can anybody help me out? I was thinking debris got into the cylinder, but why 3? I was also thinking detonation problems or maybe the spark plug was too long. The plugs where not installed. There are corresponding marks in the head.
Thanks

nwwheeler08 · Nov 5, 2012

it looks like its either a ton of pre detonation or something got in the cyl and started to distribute itself throughout the bank but some one pulled the motor before hand. whats the crank look like? also do you have any history off the motor? as in why it got replaced?

crash2 · Nov 5, 2012

What does the head look like?

leadfoot067 · Nov 5, 2012

it ate something...ive had those marks in the tops of pistons before...it happens when a screw/chunk of valve/nut/bolt/whatever gets down in the cylinder..

wazz · Nov 6, 2012

leadfoot067 said:
it ate something...ive had those marks in the tops of pistons before...it happens when a screw/chunk of valve/nut/bolt/whatever gets down in the cylinder..

I agree.
I had this happen one time after replacing a head on a Escort that had a valve seat explode. After the new head was installed I found that it had blown chunks of valve seat up into the air cleaner where it was more then happy the get sucked right back down into the new head.

CHOP SHOP · Nov 6, 2012

From the looks of those nasty cast pistons (they look even worse than normal), you just might end up with big chunks floating around.

wazz · Nov 6, 2012

CHOP SHOP said:
From the looks of those nasty cast pistons (they look even worse than normal), you just might end up with big chunks floating around.

good point!
like on that Escort I was going to try and run with just the new head and some spots on the piston that looked like that, well curiosity got to me so I decided I better pull the piston out. Thankfully I did cause I found the majority of the lower part of the piston was in the pan and the rest holding on to the connecting rod by a thread.

OffRoad Cowboy · Nov 6, 2012

I got the long block ( block and heads ) from my brother. It was a new crate engine for a van at Chevy dealer. They put it in and said it had a deep knocking sound. So they took it out and where going to send it back, but he gave it to me.
My next step is to pull the pistons and crank. So I'll update you after I do.
Thanks for the help.