Cracked Cast Aluminum Block

[mikeo56]

I'm in SW Florida, and just created a hairline fracture in a cast aluminum block in a Briggs and Stratton engine for a Troy Built generator. I turned the oil chnge screw past its bedding point. The screw was steel and the block cast Al....crack! Anyway to weld or repair this? There is a second oil drain screw so the first one can be welded or left alone.
Thanks, Mike.

 

[TVP]

It is possible to weld Al castings, but you will certainly change the mechanical properties, if the block was heat treated. Perhaps something as simple as JB-Weld will be adequate for this issue.

 

[boo1]

The Al alloys in engine block castings are typically 4xxx series. They are readily welded, consider TIG process using a 4043 rod. The issue with welding is cleaning the surface. The only really effective way to clean an aluminum casting that has been around oil in preparation for welding on, is degreasing. Methylene chloride vapor cleaning, is the most effective method.

The JB Weld might work….

 

[swall]

With either weld repair or JB Weld, be sure to stop drill the end of the crack first.

 

[attilon]

I repaired once a Mercedes 500 sport Al block by welding.
I can tell you that it can be pretty tricky.
First, it only worth doing it if that part of the block is not solicited dynamically. If that's the case, you can do the welding.
Then as the others told, stop the crack with drilling holes at the ends, and also clean the surface as much as you can.
Then there are two possibilities:
1. If there are little internal stresses due to the casting process in the block, then you are lucky and you can weld it from one end to the other.
2. If there are lots of internal stresses - this was my case - when I welded it, other cracks appeared in other places of the block, and these had to be welded as well. I only managed to weld all the cracks by welding 1 centimeter and then stop and cool it with compressed air, and then weld again 1 cm and then stop and cool... and so on. This way new cracks could not emerge, but the internal stress status surely grew. And that's why it won't hold if there are dynamical stersses.
Anyway, in any of the cases do not grind down the weld if not specifically necessary, because Al welding has micropores by nature, you will never get rid of those.
Then check the whole block with penetrating liquids.
My engine is working ok now, and I did the welding two years ago.
Good luck.