Re: Coolant Jacket + JB Weld....Good or bad.
On something that old... i'd just JB weld it. But that's only if it was for me.
I would never do it for a customers boat.
Pull your intake off (i'm assuming the crack is right underneath). Use a good heavy coarse wire cup brush on the end of a drill/grinder and don't stop untill you can almost see your reflection in the metal. Next use a small drill bit and drill the ends of the crack to keep it from spreading. Wipe it all down with acetone and allow it to air dry. Then whip up some jb and liberally press it in to the crack. I wouldn't be surprised of you went through a few tubes of it.
Having the block welded means removal and sometimes diassembly... and even then it's a shot in the dark. Cast iron needs to be torch welded using filler rods, ie~ the old school way. You can't just hit it with a mig welder, its not going to work. And torch welding is a bit old school, your not going to be able to find some kid out of a tech high school that knows how to torch weld.
Besides.... what do you have to lose by trying it? Just keep an eye on things after your done.
