Brass Brazing

[Alex94TAGT]

Do we have any brazing gurus in the house?

I'm needing to do some brazing on my cast iron engine block. I hit some water jackets in a few small spots, so I'm going to have the block baked/cleaned and shotblasted, then I'm debating on brazing it myself with an acetelyne torch. I found some fluxed brazing rods intended for this purpose.

From what I gather from various machine shops, this is done regularly. But what about the heat -- I'm obviously going to destroy the temper in the block. I guess this is ok?

The reality of it is I just need something to seal the coolant. There wont be much pressure or heat at the bottom of the block. I'm also going to back-fill the coolant passages with an engine epoxy, then I'm doing a short-fill of Hard Block. I figure this will strengthen any weakness I create by messing up the temper...

What do you think?

[Fire67]

Braze, epoxy, then some rock... Outta work out pretty good. Wouldnt it be a little stronger if you welded the areas instead. I know cast iron can be welded, Ive seen it done. To me it would be stronger than brazing because your actually fusing metal to metal. Ive always thought a braze didnt penetrate the metal, just stuck to it. I could be wrong though.

[Alex94TAGT]

Justin,

Thanks for the reply.

I haven't worked on this engine since I cut into those waterjackets several months ago. Of course, there were other extenuating circumstances, but d@mnit, I gotta get this motor finished. My goal is to have it buttoned back together in a month or so.

I own a Lincoln MIG, but I was told I couldn't just weld it because of the expansion rate of the iron. It can be done, but it's very tricky, and the weld can separate from the block. Supposedly this isn't a problem with the proper brazing rod.

I've been looking at THESE special brazing rods -- I'm not even sure if it is a brass rod, but it is supposed to work on engine blocks, and they claim it is stronger than a weld. I guess brazing is somewhat like very-high-temperature soldering, but this stuff WILL penetrate the metal and create a weld. I'll be getting the engine block far past "red hot" just to use this -- perhaps hot enough to burn a hole through it, which is why I'm concerned about the temper.

Dunno. I've never done any brazing, but it cant be that hard. My only concern is that the braze will be too fluid and just drip through the small holes I have in the waterjacket. I guess that's where the flux comes in. I'm going to do more research before I make a decision...

Thanks,
Alex

[Fire67]

Those rods look like they'd work...
The braze will definitely want to seep through the holes if their big enough, so if you have some gaps large you might want to try and "plug" the hole with a like material.
Its my understanding that brazing will seep into tight small spaces to seal and bond. Think pipe fittings, cause thats what I think when I hear brazing. Another use for brazing that Ive seen is to bond sheetmetal together in body work, but my point is that the gaps it fills are small. The flux is ususally a sheilding or bonding agent depending on the rod material.

[Alex94TAGT]

Thanks Justin.

I'm going to do more research, but I think this is the route I'm going to take. If it doesn't work, I'll just blame you, and move on to the next solution. ;D

-Alex

[Fire67]

There ya go... I get blamed for enough, one more wont bother me. Like I said, if you find the brazing material falling through the holes, try wedging a piece of iron or something into the hole to hold the braze in place

[Alex94TAGT]

Well, if that's the case, I might just go against popular opinion and weld up the darned thing. It's not like this is a major stress point -- I'm not welding a crack in the wall of the block, just a tiny 1/8" hole near the pan rail. Even if the weld fails, the coolant still has to make its way past an inch or so of cement & engine block epoxy. I think it'll hold just fine.

And I was just joking about blaming you if something goes wrong. I really appreciate the help~

-Alex

[thebird]

When i was younger all my dad had was a torch and brazing rods. Until of course i got older. $hit, i bet i was 9 or 10 when i learned to braze, of course i didnt become an expert and its been 15yrs since. It is kinda becoming a lost art if you ask me.

Although, I think it should be a good route to go as long as your not near a cylinder wall. but then if its on the outside of the block or on a water jacket then i'd say take a look at JB weld. Ive seen that hold up on diesel engine blocks before. Although i dont think either is going to penetrate the block, like welding would. Just thought you could use another option to look at. But maybe you already thought about it. I would be kinda sceptical using it... but its got to be better than getting your block red hot...

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