First, ...I know the answer is 'subjective', ...it all depends on how bad a crack, ...and where it's located. I'm curious how cracks are dealt with (especially if in a case of a numbers matching block).

I assume there are cracks that can be fixed? but, ...specifically, what area(s) of the block can one be (reliably) fixed? ...where would you not try to fix?
How reliable is a repair? (again a 'subjective' question I know...)
What are the typical/best methods to repair?

Thanks,
Kevin

We have used theis menthod for years with no come backs so far.
http://locknstitch.com/

Carl, ...THANKS for the reply ...
...I had done a Google search and was just reading...
http://www.locknstitch.com/AboutCSeries.htm
http://www.locknstitch.com/AboutLSeries.htm
...the same site you linked to : )

...just for added info for others, ...here's another page I came across that touched on a few of the repair methods...
http://www.aa1car.com/library/ar497c.htm

Imo, the best way to fix a cracked cast-iron piece is to furnace weld it! BUT you have to have a TRUE Pro do it!

The part has to be brought up slowly to temp and then welded while hot and then slowly cooled down so as not to crack or warp it! Then it has to be dimensionally checked and if needed, machined back right..

NOT an easy thing to do at all.

I would hunt up a big Diesel head repair shop and ask them where they get their heads welded/repaired if they aren't capable of doing this themselves!

Years ago when I was working on the RR I watched a Pro do this over at the Chapin Head Shop, Chapin, IL and was most impressed!!

That said, they use stitch pin crack fixing to fix just about everything and it works fine too!

And in all honesty, unless your part is super rare, it will be a lot cheaper to replace it as you probably already realize..

pdq67

PS., and btw, the guy was welding on top of an open topped burning nat. gas fired forge furnace using a loooonnngg tipped gas welding torch and loooonnnng filler rods!!

Cast iron Blocks ,as mentioned above can be repaired...it is expensive by the time machining etc is done (re decking/line boring due to warp)
Unless it is for a matching numbers car, and not going to be a performance engine, I wouldnt bother.
Cast heads/manifolds are far easyier to do.
These are pre heated either in a oven or gas axe, then arch/mig welded with cast rods, then ground off and remachined surfaces.