i've got a 71' f-250 and have had 3 390's crack a cylynder on me including my 500 horse motor does anyone know if this is a chronic problem, I'm building a 429 CJ know Im done with 390's.

 

I've heard of a few, but not many.
The folks just have them sleeved and they're good for 100k fun miles.

 

What 390 blocks are you using? I've always had great luck with 390's, but I have a 72 parts truck with a 390 that had crappy headwork and all the exhaust seats fell out. the pistons and chambers look like hamburger meat and 5 of the cylinder walls cracked. Looking closely at the cracked cylinders, the walls were paper thin and the block was only bored .030". The block was the original block from the truck (according to the original owner) and did not have the reinforced main webs. I've built several 390's using the later reinforced D4TE block with no problems. Also have many friends running the early 390 blocks with the monster main webs and crossbolt bosses, but 2 bolt mains and no problems. I've always stayed away from mercury blocks and non-reinforced ford blocks as the reinforced ones are plentiful.

 

keith craft has a main girdle for reinforcement

 

How much were they bored out? That can make a difference. Also, I think the FT has thicker cylinder walls, may want to check into that.

Sounds like bad luck to me.