Cracks in CH

[ducked]

After wipe down with white spirit, soot seems to make a pretty good poor mans crack detector, assuming Im not misinterpreting these marks.

From the way dye penetration is discussed in the manual, seems like this might be a generic Yanmar faullt, here on a 1GM10.

Since I assume theres nothing practical I can do about it (best guess desperate countermeasure would be stitch-drill and then braze with zif-bronze. I think I have some rods somewhere and MAY still have the bits of a twin carbon arc torch for use with an ac welder, but I have never used either) Im probsbly going to do nothing.

 

[Anibal]

Would you say they are cracks as opposed to fuel varnish stains? Maybe try polishing the surface or at least the surface where you see one marking, with a light metal polish to see if they come off before anything else?

 

[ducked]

Yes I would say they are cracks, though happy to be wrong.

However, not really worth investigating further this time around, since I ve put the head back on, and if they are cracks I doubt theres anything practical to be done about it anyway

 

[Mark-1]

OP, you clearly know far more about this than I do, but if those were cracks running perpendicular all the way to the exterior wouldn’t they be visible on the outside? As far as I can tell, there’s no sign of any cracking on the exterior, only on the face.

And wouldn’t actual cracks show up as thin, sharp lines rather than broadening dark patches?

If so, that does suggest Anibal may be right.

 

[dansaskip]

Don't look like cracks to me

 

[ducked]

i dont know much at all. Only diesel Ive ever opened, and if its cracked only the second cracked head Ive seen, the first being on a SAAB 900, associated with HG failure, and running between the valve pockets, as you might expect and as is probably classic.

That said, and while I am of course happy to hear its not cracked, I wouldnt expect to have necessarily seen fine cracks on the surface, because its rougher, was dirtier, I ground aluminium onto it with a sunflower oil binder, and because I didnt really look.

 

[ducked]

Clean up with pie dish aluminium. There are silvery lines corresponding to the “cracks” but only show at certain angles and not on camera.

 

[ducked]

Aluminium wiped off with white spirit soaked towel. The “cracks” ate still there, but then so is some of the varnish. Id say still look like cracks to me, but by no means vonclusive

 

[Momac]

I think there could be tracking marks . I had similar on a water cooled 2 stroke cylinder head off an outboard . The advice I received was to to carefully grind the head face on a sheet of something flat like plate glass . In fact I used a porcelain tile as the flat surface and some very fine 1500 grit abrasive paper lubricated with water. PS I also used some Wellseal sealant on reassembly.