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Old 06-24-2019, 09:17 PM
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Default Aluminum casting marks

Hey, one of my dealers sent pictures of this crankcase and he thinks it's cracked and needs replacement. I've seen these marks before but don't know the correct terminology. Any suggestions? Thanks
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Old 06-24-2019, 10:42 PM
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This may help - https://en.m.wikipedia.org/wiki/Casting_defect
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Old 06-24-2019, 10:51 PM
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Quote:
Originally Posted by MotorDoctor View Post
Hey, one of my dealers sent pictures of this crankcase and he thinks it's cracked and needs replacement. I've seen these marks before but don't know the correct terminology. Any suggestions? Thanks
Seems to me the case has taken some abuse. They do look like cracks. A Dye Penetrate test should be able to confirm if they are cracks. They can be welded to correct the defects, in IMHO.
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Old 06-25-2019, 12:08 AM
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It had been 41 years since I read those lines from a Master caster course . Looks to be a cast defect ,is there any other accompanying issues I.e. oil leaks . Other failure to the engine .
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Old 06-25-2019, 01:18 AM
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It looks like it cooled too quickly after removal from the mold, or it was removed too soon.

I base this on lead casting experience, which may not apply at all. I just know that I would get slugs that looked like that if I failed to get my mold hot enough prior to filling it, or if I dumped them out too soon...they still shot ok but they looked wrinkled...
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Old 06-25-2019, 01:32 AM
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Are you referring to all the crazing on the surface of the casting or the single horizontal line which runs across the casting about mid-frame in the first two pictures?

The horizontal line could well be a crack--have to see it to be absolutely sure. Sometimes if you apply a little heat to the crack it will expand ever so slightly. You can also tap lightly on the casting right at the line of the crack. If there is in fact a crack the sound will be a little duller with less ring than you would get if you tapped in the middle of an unbroken section. It's usually pretty easy to tell if you've actually got the thing in your hands. Dye penetrant would likely work although we rarely if ever had to use it when we were doing a lot of that work.

A welding repair may or may not work on that piece. If the aluminum is decent it will weld fine but you have to remember that inside that case are a lot of bores and bosses that hold shafts of various sizes. They all have to maintain their alignment and when you apply that much heat to the casting it is really easy to warp it enough that things simply won't line up.

I'm pretty sure the rest of those marks are casting defects. I've seen them on many thin-wall aluminum castings that we have worked on but they're not usually that extensive, or, from what I can see, that deep. I think they're a form of hot cracking or hot tears as described in the link above. They can look pretty ugly but they're almost always just surface marks that look bad but don't leak.

It's interesting that this thread appeared now. Going back 25-30 years we used to do a ton of repairs to all sorts of aluminum casting but we do almost none these days. However this afternoon someone dropped off an old Turbo 350 housing that needs some welding. Weird...
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Old 06-25-2019, 06:17 AM
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Sure looks like the casting was bad from factory. They could mostly be cosmetic, but looks like some of them were seeping oil.

Either way, I probably would be upset if I had bought something brand new, and had it looked like that.

If it did not need to be leak proof, it may do the job fine. It may have been the first one off the mold line that day, and the quality check inspector was still hung over from the weekend and passed it anyways.Click image for larger version

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Old 06-25-2019, 07:15 AM
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Those photos are of the inside of the crankcase with the oil pan removed. They sent me a couple of other pictures but I'm still trying to figure out where they took them.
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Old 06-25-2019, 09:50 AM
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The quick and dirty method of checking for cracks on a aluminum casting or for pin holes when Tig welding is:
Put liquid dish soap on the inside of the casting. Take an blowgun and blow with 100+psi air on the outside. If there are cracks or pinholes in the casting the soap will blow bubbles.
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Old 06-25-2019, 10:36 AM
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1. Unlikely any are actual cracks.
2. So what if they are they are internal to the engine and oil pan.
3. Most high volume aluminum casting are polymer impregnated to seal the casting.
4. The defects are cosmetic, most likely due to a cold die/mold.

https://www.loctiteimpregnation.com/...tal-parts.html
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