Odd Markings on Engine Block

[dwneumann]

I had symptoms of a blown head gasket on my 1966 BJ8 (but it has never overheated during my ownership). I removed the head and found evidence of combustion leakage between cylinders 2 and 3, and between cylinders 4 and 5. I measured 0.004" warpage of the head between those cylinders. I sent the head to a machine shop for resurfacing.
I then cleaned and measured the block deck and found no warpage... not even 0.001" anywhere. However, upon close inspection I found 3 or 4 tiny tiny zig-zag lines. I can't catch a fingernail or razor blade on any of these and estimate them to be no more than 0.001 deep. However, given the unusual zig-zag pattern I'm not sure what I'm looking at: are these cracks to be addressed or casting flaws to be ignored? How can I be sure?
Thanks for all advice.
p.s. I'm NOT pulling the engine and sending it to a machine shop just to have them tell me that it's nothing to be alarmed about.
Regards,
Dean

 

[red57]

They look like scratches more than cracks to me and if so, a light skim might be all you need. I have seen scratches like that when bare heads have been set onto bare blocks with a bit of small grit present and then the head is shifted/moved/slid. If it is scratches, it needs to be skimmed to insure a good gasket surface/seal.

However, you would need to strip it for cleaning if skimmed so I think it makes sense to pull it and tear it down. Have an experienced machine shop perform crack checks/assessment and then you will know if it's a worthwhile effort.

 

[NutmegCT]

Sure doesn't look like cracks to me. I'm thinking they're left from the shop's resurfacing job.

You could email (or take) the photo to the shop and get their opinion.

Breathe easy!
Tom M.

 

[dwneumann]

thank you both. They do look to me like the kind of scratches that would result from someone shifting the head over the block with a bit of small grit present. I'm thinking that a DIY dye penetrant test might be in order.

 

[roscoe]

I'm late to the party but I concur. They don't look like cracks. I've done some NDT, both magnaflux and Xyglo and have never seen a crack zigzag in two parallel lines. You could try some scotchbrite by hand or with a disc on a die grinder to see if you can make part of one of these lines go away. You can also get a dye penetrant kit at most auto parts places that will put you mind at ease. If you are unfamiliar with dye penetrant and how it works I'm sure Google will be able to educate you.

BTW, great pictures. Too often the photos people take are not good enough for a solid opinion.

 

[Michael Oritt]

I'm late to the party but I concur. They don't look like cracks. I've done some NDT, both magnaflux and Xyglo and have never seen a crack zigzag in two parallel lines. You could try some scotchbrite by hand or with a disc on a die grinder to see if you can make part of one of these lines go away. You can also get a dye penetrant kit at most auto parts places that will put you mind at ease. If you are unfamiliar with dye penetrant and how it works I'm sure Google will be able to educate you.

BTW, great pictures. Too often the photos people take are not good enough for a solid opinion.

I had symptoms of a blown head gasket on my 1966 BJ8 (but it has never overheated during my ownership). I removed the head and found evidence of combustion leakage between cylinders 2 and 3, and between cylinders 4 and 5. I measured 0.004" warpage of the head between those cylinders. I sent the head to a machine shop for resurfacing.
I then cleaned and measured the block deck and found no warpage... not even 0.001" anywhere. However, upon close inspection I found 3 or 4 tiny tiny zig-zag lines. I can't catch a fingernail or razor blade on any of these and estimate them to be no more than 0.001 deep. However, given the unusual zig-zag pattern I'm not sure what I'm looking at: are these cracks to be addressed or casting flaws to be ignored? How can I be sure?
Thanks for all advice.
p.s. I'm NOT pulling the engine and sending it to a machine shop just to have them tell me that it's nothing to be alarmed about.
Regards,
Dean
View attachment 104252View attachment 104253

I'm late to the party but I concur. They don't look like cracks. I've done some NDT, both magnaflux and Xyglo and have never seen a crack zigzag in two parallel lines. You could try some scotchbrite by hand or with a disc on a die grinder to see if you can make part of one of these lines go away. You can also get a dye penetrant kit at most auto parts places that will put you mind at ease. If you are unfamiliar with dye penetrant and how it works I'm sure Google will be able to educate you.

BTW, great pictures. Too often the photos people take are not good enough for a solid opinion.

Dean--

At first glance I too thought that the lines were scratches that could have been caused by bits of grit being dragged across the surface, but if that were the case the lines should be parallel and those are not, nor do they match the pattern of the other zig zag lines on the surface of the block.

Short of pulling the engine and decking the block I don't know how you could eliminate them, and any sanding or grinding will only make things worse.

 

[Healey Nut]

For peace of mind I would do the dye test .

 

[roscoe]

One other way to decide if they are cracks, and I still think they are not, is to see if any of them " go around the corner". By this I mean if you can see an indication that is on two adjacent faces of the base metal. When you zoom in on these, on most of them you cannot see any depth, another sign they may not be fault lines. You would be surprised how much you can see with a really powerful 20X magnifying glass and a good light source. I used to have a pocket microscope with a built in light that was very useful to me. Now they make digital ones as well. Many are under $30. Some are not very good and some work well so I won't recommend one in particular but this is the kind of thing they are often very good for. A flat well lit surface. After that, a dye check, which may be done in place remains your best bet as a next step.

Also, when I refer to lines being parallel, I'm referring to the zig zag pattern where each short zig is pretty much parallel to the line next to it. Never seen cracks that ran like that. To have more than one stress fracture right next to another that so closely matches it would be pretty weird.