Well, that is not what I planned

[240dkw]

I have had a plan to swap out the non-original motor in my car with the original, correct motor at some point and decided it was time to do it. I have been very happy with how the motor has been running, just want the number correct motor in it. First little problem I found was a broken cam oiler tube. This is very common and as I had checked the valve settings this spring and saw no problem then it is a fairly new problem. I have another oiler to replace it. 

The next problem was a bit disappointing. It seems I have developed a crack in my E30 non-emission exhaust manifold. The second photo shows the pattern of the exhaust on the back side of the heat shield. Now to decide if I try to weld it myself or pay someone to do it. 

[Patcon]

Cast iron is notoriously hard to weld. Doable but it takes the correct approach and the right welding rods or wire

[grannyknot]

and the right guy.

[240260280]

I read that Nissan cast manifolds are easier to weld as the alloy is more favourable than typical North American manifold alloys.

[dutchzcarguy]

Shot peen it is another approach.. google it..  they do this also with cracked cast iron motorblocks..  an old english? way to repair things?

[240260280]

FYI:

https://www.zcar.com/forum/10-70-83-tech-discussion-forum/116018-welding-manifold-safe.html

https://forums.hybridz.org/topic/29099-welding-cast-iron-exhaust-manifolds/

[Mark Maras]

 Been there, done that. I drilled a hole in the ends of the crack, ground a vee in the crack, preheated with a butane torch, welded the crack with nickel rod (I've also used rod for stainless steel) and buried it in dry sand to let it cool slowly.

[240dkw]

Mark: that is how most of the youtube's show it being done. Now to see if I have the wherewithal to give it a try.

Edited January 29, 2019 by 240dkw

[240260280]

This is not recommended but a good watch at 2X: https://www.youtube.com/watch?v=Pq0wfU4ZaKk

 

[Zed Head]

I'd leave it.  It looks small.  It might even be sealing itself once the manifold gets hot.  

[240dkw]

So after a very skilled welder (not me) tried a few different options, what worked best was a brazed repair. 

[Zed Head]

Nice.  Didn't even have to remove it.  I wonder if Mark meant braze when he said weld.  They're similar.  You can probably accidentally braze when you meant to weld also.

Be interesting to see how it holds up.  If you didn't pin the ends with drilled holes, as suggested, the crack might just continue to grow from the ends.  But they'll be small cracks.

https://www.machinedesign.com/fasteners/when-brazing-beats-welding

https://www.lucasmilhaupt.com/EN/Brazing-Academy/Metal-Joining-Welding-vs.-Brazing-vs.-Soldering.htm