The Stovebolt Site Forums The Shop Area Engine Shop Welding a cracked block

What is the thinking on repairing a cracked block? I know it depends on the situation, but does it work? The engine shop said they could groove out the cracks and have it silver soldered. I hadn't heard of this technique before.

Thoughts everyone?

An external crack in the water jacket can be brazed. I've done a bunch of them. Silver solder? I've never tried that. Be sure to find the ends of the crack and drill a hole to prevent it from extending itself as the heat is applied to fuse the brass to the cast iron, and be sure to grind the block smooth for about 1/2" on each side of the crack so the brass can make a good bond. Otherwise, it will leak coolant by following the rough casting surface. Once you've got a good bead of brass built up and fused well, the surface can be dressed flat with a coarse-grit sanding disc and the patch can be painted over. If you want to hide the repair completely, spread a thin layer of Bondo over it and press a piece of 40 grit sandpaper to the patch after it's about halfway cured. The texture of the sandpaper will transfer to the Bondo and hide the repair completely once the block is painted.
Jerry

I've seen on some site where they fix them with overlapping pins in the crack. But I like Jerry's idea also....

John

It's amazing what a skilled craftsman can do. If somebody knows what they're doing its real doable. If you're considering paying a guy to do it ask him/ her if they guarantee their work. Watch them close. If they hesitate, run. If they say absolutely, and can do it without hesitation, do it.

Thanks Jerry and everyone,I am still on the oil and water adventure with the head and am worried about the block too. I plan on pulling it as soon as possible and getting it checked. The head was cracked in three cylinders and the gasket appeared to be leaking as well, not to mention the exhaust manifold leaks.

Not a good news week for my 46, lots to re fix after sitting for a long time and I still have to get the body work going. I am back at square one.

I use the "stitching" method, using overlapping threaded plugs. The real advantage is that it doesn't require any heat. I've used it successfully on a crack across the top of the block also, where welding could cause warping.
Doesn't take any special tools, just patience.

Dad was following too close behind a truck that lost an outside dual,when I was a kid. tire was still upright,when he ran over it,in a '52 Pontiac,(straight 8). Didn't damage the sheet metal,but wrecked the radiator,and both manifolds,plus cracked the block. He had a shop "stitch" the block,and the manifolds. Held-up for 10 years,until he junked the car. I've had real good luck with JB weld,too,as long as you grind the crack,like Jerry suggests. The key is the curing process. Apply a 100 watt bulb,(explosion-proof trouble light),to the repair,and let it set-up for at least 12 hours. We always allowed 24,just to be double safe. We repaired a dozen,(or so),using this method,and never had a customer return with a "repeat offender". just the normal tune-up,brakes,etc. hope this helps.

I think I like Jerry's method the best. Especially yhr 1/2 inch smoothing along the margins. It is also fits with what the shop is experienced with and has suggested. I don't get the silver soldering concept, isn't brazing stronger/ better than solder? At some point I will get this done, but not untill I check my existing block and it it is cracked, I will have it fixed first.

I think that silver soldering is used for refrigeration line fittings. I know that things have to be really clean for it to stick and it requires lots of heat to get it to flow into the joint. I don't think it is suited very well for cast iron, not sure how a person would get the cast clean enough and I would be nervous about the amount of heat needed. I know that brazing takes less heat and the flux used is more forgiving with the dirty properties on cast iron.

Sorry, Don- - - -Brazing takes MORE heat to melt the rod than silver solder and a different type of flux, and the metal needs to be just as clean as it does with silver. At least that's the way it was for the 20-something years I taught a night-school welding course. Silver is a lot more suitable for copper, though.
Jerry

People often say 'Silver Solder' when they mean Brazing which uses a Brazing Rod who's composition contains some small amount of Silver.


Anyway...where is the crack located on the Block?

Thanks for clearing that up Jerry, I must have got my wires crossed up. Used to help a a/c repair guy when I was in high school.

The Crack is on the manifold side of the block in the center section. it is on the front side of what is a raised ares that looks like something would screw into it. I think it could be a second position for the throttle linkage pivot or the pivot point, not sure on this block.It is a very fine crack and circles this raised area. About three inches long. Tthe shop found it when I had it magna fluxed

Does it leak?

I used lock and stitch. My crack was from the petcock to approximately where the exhaust comes down. You can go on You tube and see their demonstration on how to do the repair. First you would want to make sure all of the mud is out from the bottom of the water jacket. It actually hardens like a rock in there, so some picking is necessary. This is why mine cracked. Anti-freeze could not reach it. Much easier to do with engine out, then you can replace all of the freeze plugs. Look at my pics of the engine. You can not even see the repair. Good luck in your endeavors.

Check this "Young'un" out...http://www.youtube.com/watch?v=Yopcz-IYDyQ "Welding cast iron Without Pre-Heat" One of your pupils,Jerry?

Interesting technique! The problem with skip-welding like that is there's a definite possibility of getting seep leaks of coolant where the welds overlap. Here's an obscure little fact some folks don't know- - - -once a root pass of nickel welding rod is laid down and well-bonded to the cast iron, regular mild steel welding rod can be used for an overlay. I like #7014 rod for a cap pass over the nickel rod. 7014 can be run with an AC buzz box welder like the little Lincoln tombstone style welder, and the bead lays down flat with a slag layer that curls up and almost falls off by itself. I like to post-heat the workpiece with a torch, and then bury it in a pile of sand overnight for a slow cool-down.
Jerry

Nickel rod, is it for DC or AC welders?? John

It works best on DC, reverse polarity like 7018, but AC will do a pretty fair job. The bead just isn't quite as smooth.
Jerry

Jerry,You "DA MAN"!! I APPRECIATE ALL YOU DO,to help people on this site! I like your idea! A bit more insurance against further cracking- BRAVO!!

Consider the cost.

A repair vs a tested replacement block.

Can all this welding magic be done for less than $250 or so? One or two $100 more and you can have a crack free block.