I replace my head with a junkyard head. After setting the valves and getting it worked on by the machine shop I noticed what appears to be a hairline crack. I'm not 💯 sure that it's a crack or casting mark. I think that whatever it is it shouldn't be a problem.

 

Where exactly is that? The shop should have magnifluxed the head.

 

It's below the injector cup

 

Has the head already been installed and torqued?

 

No but the injector cups have been installed and valve job ready to go in

 

Thats a hard nope........

Until proven otherwise, but doubtful you could convince me to put that in.

 

Not sure what machine work has been done. Did the machine shop pressure check the heads? Did they install the cups? What did they recommend?

 

Isn't the deck directly opposite of what we're looking at? If the head isn't installed flip it over look at the other side. If there's no hint of even a shadow of what we're seeing on this side on the other side, it may not be conclusive but, it'd go a long ways toward easing my nerves

 

Dye penetrant
unless you have a magnuflux.

 

I thought he said the cups are already in place. If so the cup would have to come out to access the questionable area. Of course that is easy enough if the head is on the bench and the price of 1 new cup is nothing compared to what you'd be looking at if it's bad and goes into service.

 

If it's cracked it should be cracked through to the opposite side.

Personally, I'm not going through the effort it takes to install it without Magnafluxing it.

 

I learned the hard way on my rebuild there was a crack up in the glow plug hole, that wasn't visible and caused my engine to overheat and dump coolant into one of my cylinders.

I would give it a hard pass on that head and find another one, or you'll find yourself tearing into your engine again like I did.

 

I vote look for another cylinder head as well. Any crack is a ***** in the armor.

 

I'd not run it. Best case scenario you get to replace it a little down the road. Worst case, you get to replace a bunch more.