Cracked exhaust manifold (1 Viewer)

[Nado FJ]

I've known it has been there for a while, but it is time to get around to the crack in
my 1977 exhaust manifold. Any way to fix something like this or do I just have to suck it up and look for another manifold? Any advice would be appreciated! Thanks, Paul

 

[reddingcruiser]

Welding cast iron is quickly becoming a lost art. Your best option is to look for a replacement in good condition. I would have it magna-fluxed before I shelled out any cash, just to be sure it's "crack free".
If you decide to have yours welded, do your homework and look for people/shops with a proven track record with cast iron, 'old school' guys (blacksmiths) are usually the best. I had a blacksmith weld up a broken vise years ago and I never had a problem. Still, there is more risk in the welding approach.

 

[3_puppies]

is that the thermo nuclear reactor setup? go as @reddingcruiser suggested and just replace with good used. I don't have to deal with smog but I thought CA officials were accepting the later manifold with no issues as the exact replacement is not available.

 

[Pin_Head]

Good used one is good solution. Brazing works well. I brazed a crack on my thermonuclear reactor manifold and it lasted 10 years.

 

[iptman]

I replaced my TR manifold with a Fed spec unit out of a FJ60. Had to swap the EGR pipe as well.

 

[Nado FJ]

Thanks for the advice everyone. I figured I was up the proverbial creek. It gets tough when you start dealing with finding the much rarer post-8/76 manifold. Doesn't seem to be a lot of options out there that won't break the bank. Just sold my other project (FJ80) because this FJ40, although I love her, has been cleaning me out!

 

[shawnfj40]

There are a ton of the manifolds kicking around. Every v-8 swap you see out there is a 2f looking for a new home.

 

[Nado FJ]

There are a ton of the manifolds kicking around. Every v-8 swap you see out there is a 2f looking for a new home.

Good point!

 

[Pin_Head]

You will need the front half of the exhaust pipe too.

 

[DougAustinTx]

If you want to try to repair yours, clean the area with a carbide die grinder to get to clean shiny metal. Then use a stick welder and get some nickel rod made for welding cast. It isn't vey expensive and you only need the bare minimum they will sell you. Do small fast welds and don't let the manifold get too hot at one time. I weld broken ears on exhaust manifolds fairly often. Sometimes I have to build up the entire missing ear with the rod. Bear in mind that the repair will be much harder metal than the cast iron and if you have to drill and tap the repair, it will take some sharp drill bits and taps. On your crack, just clean the area, groove the crack with a die grinder and do small hot welds, letting it cool between welds. If you build up the heat too much in a small area, then you get into the problem of differential expansion and you develop more cracks.

 

[White Stripe]

Manifold cracks can be caused by worn out motor mounts that allow excessive engine movement. Rock auto sells fj40 motor mounts. The DEA brand are the cheapest, they are also the company that makes the mounts for Toyota but getting them through rock auto you save about 40 bucks per motor mount.

 

[iptman]

Mud member @harry_apple mocked up a flange for me for my manifold swap. He sells them on this website for $20. I went 2.5 from the manifold back.

EXHAUST FLANGES

 

[Nado FJ]

If you want to try to repair yours, clean the area with a carbide die grinder to get to clean shiny metal. Then use a stick welder and get some nickel rod made for welding cast. It isn't vey expensive and you only need the bare minimum they will sell you. Do small fast welds and don't let the manifold get too hot at one time. I weld broken ears on exhaust manifolds fairly often. Sometimes I have to build up the entire missing ear with the rod. Bear in mind that the repair will be much harder metal than the cast iron and if you have to drill and tap the repair, it will take some sharp drill bits and taps. On your crack, just clean the area, groove the crack with a die grinder and do small hot welds, letting it cool between welds. If you build up the heat too much in a small area, then you get into the problem of differential expansion and you develop more cracks.

Thanks for the great advice. Unfortunately, I have not gotten into welding yet. It looks it might be a necessity soon though given some of the other issues on my rig!

 

[Nado FJ]

Manifold cracks can be caused by worn out motor mounts that allow excessive engine movement. Rock auto sells fj40 motor mounts. The DEA brand are the cheapest, they are also the company that makes the mounts for Toyota but getting them through rock auto you save about 40 bucks per motor mount.

Great point. I really should put the engine and start from the beginning.

 

[Nado FJ]

Mud member @harry_apple mocked up a flange for me for my manifold swap. He sells them on this website for $20. I went 2.5 from the manifold back.

EXHAUST FLANGES

Thanks!

 

[Pin_Head]

I wouldn't weld cast iron unless you do it properly, like Dick said above. This means heating the whole thing up to about 1400F, welding the crack with cast iron filler and then letting it cool slowly below 600F, like 1-2 degrees a minute.

If you don't do it this way, it will eventually just crack no matter how you weld it or with what you weld it. The reason is that just heating it alone to 1500F or more and letting it air cool makes it brittle.

 

[Nado FJ]

I wouldn't weld cast iron unless you do it properly, like Dick said above. This means heating the whole thing up to about 1400F, welding the crack with cast iron filler and then letting it cool slowly below 600F, like 1-2 degrees a minute.

If you don't do it this way, it will eventually just crack no matter how you weld it or with what you weld it. The reason is that just heating it alone to 1500F or more and letting it air cool makes it brittle.

That sounds above my skill level, but would love to see it done. Thanks!

 

[shawnfj40]

Pin_Head nailed it. For the time and expense of doing it right, why not just replace it. I could see going the extra mile to save a 1902 ford manifold or something but not something so plentiful.

 

[Nado FJ]

Pin_Head nailed it. For the time and expense of doing it right, why not just replace it. I could see going the extra mile to save a 1902 ford manifold or something but not something so plentiful.

I agree. I just haven't seen anything local in Southern California. Hopefully something will come up!

 

[Mace]

That is not a "typical" 2F manifold. But a Cali spec manifold.

It's not that plentiful compared to other 2F manifolds.