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Welding an engine block

CJ: 
2K views 15 replies 11 participants last post by  chadcooper55 
#1 ·
The block on my inline 6 cracked. Wondering if anyone knows what kind of rod I will need to weld it?
 
#7 ·
You need a nickle rod to weld cast iron. To do it you need to preheat the block to 550 degres and cool it slow. I usually wrap it in a welding blanked and let it be. On the crack v it out good and drill an 1/8" hole at the end of the crack to stop it from spreading. I know this is not what you were looking for being an assembled motor, But it is the proper way to weld cast iron. also be aware, welding can arc between your bearings in the crank and pistons to cylinders ect.
 
#8 ·
so keep your ground as close as you can to the spot you're welding.

also, if it's just a water jacket you can use JB weld, buddy of mine had an old 79 blazer with cracked water jackets that someone just plastered JB weld all over the side of the block, it was compleatly fine until you started beating on it alot and it'd leak a little bit.
 
#11 ·
I've welded three blocks while in the truck. I used a high nickel content rod. I never did any preheating. I did drill small holes at the ends of the crack and all has been fine. They all are on the road still. One was in father in laws dodge. His cummins had a three inch crack just above the oil pan. That one was a pita due to oil seeping thru the crack. Was very hard to get it clean enough to weld it. If your not sure about welding it I'll help you out if need be.
 
#12 ·
Thanks for all the advise guys. Does anyone have any specific specs for the rods? Like what numbers and stuff? Just want to make sure I get the correct amount of nickel and what not so it is a good weld and will hold for a bit. Granted this jeep is my toy, but I don't want to be redoing it. And it is cracked below the exhaust manifold, far enough down to just have to pull off the fender and the exhaust to get to it. Made the mistake of leaving water in it over the winter.
 
#16 ·
If you don't preheat it and arc weld it you are asking for problems. To arc weld cast you must preheat, weld, peen to distress, post heat and cool very slowly. If you do not do that you are asking for stress cracks and you completely wasted your time. I would be curious to see how some a2 bronze tig rod would work If you can get it clean. A softer more pliable fill rod wont stress the cast as much. If you insist on arc welding I would pull the belt off so you don't run a dry water pump and fire the motor up until it is good and warm (borderline over heating). Then I would weld and peen with a center punch to de stress it after every rod. After I was done welding I would fire then motor up and let it warm up a bit and shut it back down quite a few times so it cools very slowly. Also as somebody else stated make sure to drill the ends of the crack or it will continue to crack. A good even preheat with a very slow cool down is very very important and don't let anybody tell you otherwise. It is especially important because you can't get it to the full temp that you really should have to repair it correctly.
 
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