Hi guys,

I need some help. So i’ve been hearing a knocking noise coming from the oil pan. I took the spark plugs out and put in the borescope. The pistons seem to have carbon buildup and slight rust. Cylinder #2 wall has 2 vertical scratches and Cylinder #1 has some horizontal dot indents.

I guess my question is how concerned should I be?

Cylinder #2







Cylinder #1

 

It isn't the pistons knocking......

 

I checked the flywheel and everything was tight so I dont think its that either. I’ll post a video of the knocking when i get home.

 

As said earlier that scratch and those strange dents are nothing to worry about, the knocking may be something to worry about.
it might be a secret but could be useful to know how many miles are on the engine and what the oil pressure when it's hot is.

Keep in mind that with your model year the 331 head/ bearings/oil pressure can be an issue.

 

I dont know about the dots, but it appears to me the bore is showing cross-hatch, so that is either OEM or it has been honed

I guess the vertical scores may be the result on an original non-rebuilt engine that has sucked i small bits of debris over the years

If I was you, I would perform a compression test and monitor oil consumption (easy)

Technically, it would be best to perform a "leak down test" as this will indicate by % whether each cylinder is a pass/fail

 

It has about 216k miles on it and at idle oil pressure is between 20-30psi while driving it sits around 40-50psi
I also did a compression test and each cylinder is giving an about 130-135psi reading

 

OP is ok, and I cant recall spec on compression

On the face of it I would not consider take apart that motor unless more than 10% below spec...even then probably not, as it will need a complete rebuild

If you are worried about bearing wear, have your oil tested, which will show high levels of certain metals if the bearing is too far worn

Knocks get worse. You should be able to narrow down it source with an engine stethoscope (or screwdriver)

pull one plug at a time gives a clue which cylinder

 

Im going to send oil to blackstone for testing and see what comes up.

i used a very long flathead and noticed that the noise was the loudest toward the back end of the oil pan.

I already have planned buying another engine to rebuild while i use this one.

​​​​​​​i really appreciate the help, ill report back with what i find.