Advice needed on manifold repair

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Brooks James

Brooks James

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Got this in a swap

lots of cracks

Wasn't too interested till I found out it's 68-70
340.

Isn't this the best 340 manifold or was the 71 better

Looks like someone attempted a jb weld patch on the back of the manifold

I have never seen a manifold crack this extensively

Not concerned that it will appear patched

Was this one of the manifolds Mopar copied or vice versa

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All 340/360 4 barrel manifolds are very good. Take it to someone who can weld cast iron and get an estimate first, then you can make a good decision. For me that would probably be too much, but I have had exhaust manifolds welded with at least 40 years of service and still holding up fine.
 
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66fs said:
All 340/360 4 barrel manifolds are very good. Take it to someone who can weld cast iron and get an estimate first, then you can make a good decision. for me that would probably be too much, but I have had exhaust manifolds welded with at least 40 years of service and still holding up fine.
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I have very little in it, $150 to fix would be worth it to me
 
Brooks James said:
I have very little in it, $150 to fix would be worth it to me
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Remember, even if you can get it welded up for $150, you'll also have to spring the coin to have all the gasket surfaces re-machined, and then need to use thicker gaskets to make up for it... and if you plan on using a big carb on it, you *may* need to have the throttle bores opened up.
I'm all for saving the good stuff if I can, but there comes a point where the cost to repair exceeds the cost to find a different good original.
 
If you get it welded up, just remember that there may be cracks you don't see until it's bolted down and heat cycled a few times. You may end up down the rabbit hole.
 
You should be able to find a "2100" manifold.. I wouldn't use that... air leak is one thing //coolant leak into a running engine is going to cost you more than a manifold !!!
 
Lets call it what it is. JUNK!. Welding that would be a waist of your money. Looks like it was on an engine that was full of water and froze. I bought this on Facebook for $25. then glass beaded it. Take your time and search for another intake. You'll thank yourself in the end .



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I think the 71 was a spread bore manifold, so that one is different.

Seems like there are used aluminum manifolds around not much more than the repair cost. Shipping is a killer though.
 
Both are spread bore manifolds.

It’s a project type repair, be prepared to be frustrated. Still good wall art thought.

If you are bent on repairing and using it, consider brazing it. Anyone with a torch can do that. It needs to be thoroughly stripped and cleaned, then checked for the cracks. You can get kits from a moldmakers supply house. If your lucky, the cracking itself didn’t distort the machined surfaces. If not, it will need to have surfaced to the head cut.

The 71 is a better manifold and easier to port from the top.
 
Oldmanmopar said:
... Looks like it was on an engine that was full of water and froze. I bought this on Facebook for $25. then glass beaded it. Take your time and search for another intake. You'll thank yourself in the end .
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Thanks, I was trying to figure out how that happened.
 
That thing will warp like a potato chip with all that welding. Even with preheat and welding very slow.

If I was going to try and save it, I would pin it. You can buy the pins on the internet and you can easily do it at home by hand.

Not saying it would 100% fix it, but pinning stuff like that is a better option IMO.
 
when people talk about manifold door stops on here, this is what they mean.

you could repair it, but the cost to do so would far outstrip what you could source another one for. and even then, i'd be wary of any aftereffects-- ie warp from repair, unseen damage that didn't get repaired.

unless it was 1000% numbers matching car with crazy low miles and super duper OG, then that thing is fit for the bin.
 
junkyardhero said:
when people talk about manifold door stops on here, this is what they mean.

you could repair it, but the cost to do so would far outstrip what you could source another one for. and even then, i'd be wary of any aftereffects-- ie warp from repair, unseen damage that didn't get repaired.

unless it was 1000% numbers matching car with crazy low miles and super duper OG, then that thing is fit for the bin.
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Yeah, that would end up on my "keeper" junk pile. I've got some mismatched junk heads, a cracked 318 block, etc. to go with it. Someday I'm going to clean them all up, put it together and make a coffee table out of it. Well, if I can sneak it in past the wife...
 
Professor Fate said:
Yeah, that would end up on my "keeper" junk pile. I've got some mismatched junk heads, a cracked 318 block, etc. to go with it. Someday I'm going to clean them all up, put it together and make a coffee table out of it. Well, if I can sneak it in past the wife...
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the war department will never know!

(oh, and put it on casters. my back hurts just thinking about moving that thing!)
 
There's no distortion on the intake port crack, or other shift that would require machining. I'm thinking about about what CH 1 II said about brazing it. I had good luck with that before. I have practically nothing in it.
 
Brooks James said:
There's no distortion on the intake port crack, or other shift that would require machining. I'm thinking about about what CH 1 II said about brazing it. I had good luck with that before. I have practically nothing in it.
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Good luck!
 
Brooks James said:
Some of the best advice I got was when I was a CPY in the Army and I was in an extremely frustrating situation and full bird Colonel told me "don't ever give up".
It has served me well but has also bitten me in the ***.
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If it's your life on the battle field, that's different. "Attempting" to fix that manifold just doesn't make good sense to me. I'll say it again, goid luck.
 
If that was just a crack and a manifold worth fixing and you were capable of drilling the end of every crack it’s doable. But that thing is crack in many different directions and even after welding it you would have to magniflux it to see if you caught everything. Do yourself a big favor and write it off as a learning experience.
 
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