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Old 11-11-2021, 02:28 PM
orwell84 orwell84 is offline
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Default Question on oxyacetylene aluminum welding and brazing

I know this isn’t metal shaping but I was wondering if it would be possible to weld or braze this with oxyacetylene. It’s an aluminum Vespa engine case.

I would like to build up the case with welding around the cylinder spigots so I can add/enlarge the transfer ports. A lot of Vespa tuners use JB weld if porting breaks through the case, often with good results if it is prepped properly. I would rather use metal. I don’t usually weld aluminum so I don’t have a TIG welder. Is this possible?
EC119290-6258-4438-8CD7-03729A8EC512.jpg

4597953C-9C4B-4FB8-80BA-6C8E9905C25E.jpg
Thank you for the help
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Last edited by Steve Hamilton; 11-11-2021 at 09:09 PM.
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Old 11-11-2021, 06:05 PM
DarkLightning DarkLightning is offline
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It's an alloy, but I don't know the constituents. I'd caution against using a torch. One of my brothers had a Husqvarna, which had a case of either magnesium or a high enough magnesium content that the "welds" were quite spectacular. The weldor pretty much destroyed it, though that was electric welding. That may be why JB Weld is used?
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Old 11-11-2021, 07:04 PM
orwell84 orwell84 is offline
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It’s definitely aluminum, but I don’t know the specific alloy. It’s from the early 60’s and was successfully TIG welded recently. These cases are routinely TIG welded for port work and rotary pad repair. I was hoping to be able to do it myself, though getting set up for TIG isn’t worth the expense for me. JB weld or a similar type epoxy is actually recommended in factory manuals for rotary pad repairs. I just never liked the idea of using JB weld on an engine case. They are very sturdy cases. I recently split one with seized internals that looked like it had been a doorstop for a barn door for decades. I heat and beat the snot out of it as it owed me nothing. Lo and behold, it didn’t crack, no real corrosion of the aluminum inside, rotary pad was fine. It’s a keeper!
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Old 11-11-2021, 10:44 PM
lots2learn lots2learn is offline
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It can be done with flux. But if you dont have a lot of experience with Oxy Aluminum welding I would suggest some of the lower temp fillers. They will probably work if epoxy is holding up for others.

Sorry I dont have any experience with them so cant tell you any brand names.

If the case was magnesium you could weld it with Oxy also. In WWII they did not have TIG for Magnesium so used torch.
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Old 11-12-2021, 07:35 AM
dwmh dwmh is offline
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Yes it's possible, I have welded aluminium engine blocks using oxy acetylene and preheat. But if you get it wrong you could melt the lot. I should practice on some scrap before even thinking about it.
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Old 11-12-2021, 07:57 AM
orwell84 orwell84 is offline
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Quote:
Originally Posted by dwmh View Post
Yes it's possible, I have welded aluminium engine blocks using oxy acetylene and preheat. But if you get it wrong you could melt the lot. I should practice on some scrap before even thinking about it.
Thank you. The lower temp aluminum brazing I’ve seen uses Mapp gas. It does seem to need preheating of the case to work, but I doubt it’s as strong. It looks more like soldering than brazing to me....no capillary action... I used the mapp torch a lot to separate the cases. I can see why oxyacetylene would be touchy if you are truly welding by melting and flowing the base metal.

Maybe better to just have it TIG welded. The gentleman who did the crack in the cooling vane did a nice job.

Sometimes it’s better to hand it off and admit that you can’t do everything, though it’s worth trying out on something easier to replace than a 60’s engine case.7770CCDB-37D2-4478-9CE4-5A8CC91495EA.jpg

Thanks for all the helpful replies.
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Last edited by Steve Hamilton; 11-12-2021 at 05:02 PM.
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Old 11-12-2021, 01:42 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by orwell84 View Post
Thank you. The lower temp aluminum brazing I’ve seen uses Mapp gas. It does seem to need preheating of the case to work, but I doubt it’s as strong. It looks more like soldering than brazing to me....no capillary action... I used the mapp torch a lot to separate the cases. I can see why oxyacetylene would be touchy if you are truly welding by melting and flowing the base metal.
Thanks for all the helpful replies.

It's do-able.
You are right - the MAPP gas fixes are done with ALUMINUM SOLDER, low temp, soft, - but they do not admit it because they prolly don't know.


Students of mine have learned and practiced enough to report their successes using O/A and aluminum welding on Castings .... auto tans cases, engines, saws, etc. etc.
Lots of misinformation out there. But it is free info..... gotta love freebies.


Vespa is what year?
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Old 11-12-2021, 04:40 PM
crystallographic crystallographic is offline
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Hmmm,
I'm seeing one tig weld on the rim, right side.
What goes in the rotted-out center - a machined plug?
I think 4043 filler and Super Premium flux, and some .edu would get this done.
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Old 11-12-2021, 05:02 PM
orwell84 orwell84 is offline
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Thanks! Vespa is a 62 VBB. The running engine is from a 65 Super. The rotted out plug is part of the old bearing seal for the crank. It was rusted to the crank. The main bearings are roller type and fit into a brass bushing in the case. Heat the case on a hot plate a little and it just drops right in.

I will check out the 4043 filler. The areas around the transfer ports are low compression/pressure.
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Old 11-12-2021, 05:26 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by orwell84 View Post
Thanks! Vespa is a 62 VBB. The running engine is from a 65 Super. The rotted out plug is part of the old bearing seal for the crank. It was rusted to the crank. The main bearings are roller type and fit into a brass bushing in the case. Heat the case on a hot plate a little and it just drops right in.

I will check out the 4043 filler. The areas around the transfer ports are low compression/pressure.



Roller crank bearings = cool stuff.
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