Crack in Aluminium Crankcase (MIG help)

Your beetle block is likely a magnesium alloy. It is not impossible to weld but certainly difficult. To do a proper job it will have to be TIG welded. Every bit of oil contamination will have to be removed. Argon shielding is standard. Unless you have done this kind of repair before it would be unlikely you would be successful at sealing the crack. Randy

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No, this is definitely aluminium alloy as it's a late (Mexican) case. Early cases were magnesium though.

It is not impossible to weld

The case was cleaned thoroughly before I cracked it so there shouldn't be any oil contamination unless it has absorbed into the metal due to porosity.

Grrr :'( Cheers for the reply Randy. I shall try "Quick Steel" or something similar if there's no other advice to be gained here. Or I suppose it's pay someone ;-)

I know I did a Bad Thing (TM) live and learn :¬) I would like to be able to rectify my own mistakes if possible though. I have just signed up for a course that covers a bit of TIG. I like getting in there and learning. My local TIG welder shut up shop a while ago. The hunt will continue, I'd like someone who will let me watch & learn at the same time.

If the case is bare (and it should be if you're drilling on it) take it into your class after one or two sessions and ask the instructor for help.

If your case is an aluminum alloy and really clean you might get by with welding it with MIG. Vee out the crack, put a backup plate behind to support the material and prevent melt through then wire feed weld it. Someone might be able to recommend the suitable alloy. If it is a die cast alloy it might no be regular aluminum alloy but a zinc aluminum which is difficult. From the sound of it all you need is a small spool of aluminum wire. If you are going to glue fill repair there are some excellent products that will take the heat also. Shop around before just grabbing the first avialable. Randy

Unless you are prepared to pay £2000 for a reasonable AC/DC TIG machine, then going on a course doesnt seem to be that much use.

You can certainly pick up the basics of TIG welding on a course, but I found it was really a matter of practice, practice, and more practice.

ken

Thanks for all the replies guys!

I have another 'gash' case so I shall practice with ally wire in the MIG. I have also found where I can get HTS-2000 in the UK. So I have a couple of options.

UK supplier is

It's not a highly stressed area which is fortunate and it's just a hairline crack. Will V it out as Randy has suggested.

Thanks for the input.

Being a big Volksie aircooled freak, this is a subject near and dear to my heart.

Being a big fan of the Zimmer, when the Man speaks, the freak listens.

A quick google search of the web at:

AS21:

4.3% Al .35% Mn

I assume that "Mn" is Magnesium. If so, and if the analysis is correct, then you will see that the AS21 alloy contains even more magnesium than the As41 does.

Therefore, just as Randy states, this is a repair worthy of being done with square wave TIG and by a consummately experienced weldor.

Gentlemen, start your welders. Fix your engines. Then start your engines.

Vern> Your beetle block is likely a magnesium alloy. It is not impossible to weld

You need to worry about porosity if the crack and weld is near fluid under pressure. What I've found welding (using Tig, not Mig, but the theory probably transfers) old dirty aluminium is that you can put a bead down, grind it out, put another bead down, grind it out, and each time you add new filler you get a cleaner base to work with, and the last bead is perfect.

Brian

AS21 and AS41 type 1, 2 and 3 cases are magnesium alloy with a very small addition of aluminum. "Mn" is manganese. Type IV cases are aluminum. AS41 alloy was supposedly used for casting later VW engine cases and replacements since it was more resistant to age-hardening and cracking, from what I've read.

I've got a couple of old books on aircooled VW engine building and modification, one of the books details how to weld up cracks in engine cases and heads. Unfortunately, they're buried in the heap and I don't remember the author or title right off hand. It also detailed when the changeover in alloy types was made and what other mods were made to the engine cases during production over the years.

Warpage is the big problem, IIRC, they built a fixture to bolt the case half down to first, then preheated the works in an oven before welding. Used cases had to be carefully solvent degreased before welding. Even then, there were problems with the welded areas cracking again. In some cases, a small plate was welded over the area instead of trying to weld the crack up. They used TIG with the proper filler for magnesium, I'm not sure what would happen if you used an aluminum filler rod instead of the right stuff. Looked like a job for the pros to me.

Stan

Good point and likely a fire hazard too. Randy

The site you quoted is a bit incomplete, it didn't list the Magnesium content!! Matweb comes up with this for AS41

Mn is Manganese

Vern> Being a big Volksie aircooled freak, this is a subject near and dear to > my heart.

Well, I ran the repaired Brodix head with a fix on the #7 cylinder. I had to fill in a spot where a valve dropped and before going through the piston gashed the top of the combustion chamber big-time and it is right near the area the cylinders meet and snapped off and tore up everything. So I had to fill that back in, machine it back down on the Sunnen and c.c. the head back down after I got the chamber cleared. (202/186 so you know the valves are super close) I don't have any problems with it. All the EGT's remained consistent, I did have a problem indexing the plug at first because when the valve let go naturally, the plug got mashed up and I had to heli-coil the plug. That was a bitch but I drilled out the coil, used the filler and tapped it clean and It's now back on the shelf after I magnafluxed it and there is no problem I saw and I had two guys re-check it after I left and we are all in agreement, this is a solid fix for the head. I ran out of three MAPP cylinders but it salvaged a $1500.00 head. Proof is in the pudding. The heads will be back on the car Tuesday when the new block shows up. I'll append this once we get a few runs on it too. We had to knock off the dyno as mine is now being moved and I have work backed up.

All the best guys,

Rob

Fraser Competition Engines Chicago, IL. Long Beach, CA. ( Soon!)