[FirstEliminator]

Hey guys,

What I have is a cast iron exhaust manifold that has a crack. The easy thing to do would be to replace this manifold. However, it is original to the car with the correct date code and in excellent shape minus the crack. The repair I am looking for needs to be not visible. A row of dimes would be o-k on just about anything else, but appearance is important on this. I'm trying to determine what is the best approach this repair? A couple thoughts are heating the manifold above brass melting point and trying to feed brazing rod into the crack---like soldering in a way. Or pre-heating and welding then cleaning and blending. The gasket surface will also be milled or surface ground for flatness when done. A line of brass would be visible, but the manifold will be painted with high temp exhaust paint before installation.

What would be the best course of repair for this?

Most things I try to do myself, but I believe this process is delicate and the part is important. Maybe sending this to someone with the proper equipment and experience would be the best way for repair.

thank you,
Mark

[cj737]

Give this a watch -

https://www.youtube.com/watch?v=xQN_yz-4Hhg

[FirstEliminator]

hi CJ737,
I've seen that episode before. Jody did say he thought it wasn't a good repair for a manifold that goes through heating and cooling cycles.

[cj737]

The best approach is nickel rods, preheating the manifold, cleaning it REALLY well, then post-weld controlled heat/cooling. How in-depth are you willing to go?

[FirstEliminator]

How in depth?---well, I was looking for a heat treat oven for a while to be able to preheat and control cool this part. But, I think sending it out might be the best bet. Just not sure where.

[cj737]

You probably don't need a fancy oven. Preheat to about 500* (household oven will do if the wife doesn't kill you). Thermal blankets for the controlled cooling. You can grab those from online sources maybe even a decent local welding shop. Got pictures of the manifold showing the damage?

[BugHunter]

Jmho here, op is obviously welcome to do as he wants...

Unless this is some one of a kind, uber-rare 100 point car, which I doubt since he's said manifolds are available to buy new, then I'd just buy a manifold and be done with it. Ymmv.

Often times, folks go off the rails keeping old crappy parts on a car that's old just because of some wives-tale about 'original parts'. They don't stick serial numbers on exhaust manifolds, and they'll be rusty in no time anyway. And I say this as an owner of a rather collectible car.

[drizler1]

You probably don't need a fancy oven. Preheat to about 500* (household oven will do if the wife doesn't kill you). Thermal blankets for the controlled cooling. You can grab those from online sources maybe even a decent local welding shop. Got pictures of the manifold showing the damage?

I welded my vise in our propane barbecue . It’s a large barbecue though. Got it hot, hit with the rosebud. Welded tapped with hammer ,rinse and repeat Till done. Lots of intermittent tapping Then tossed in a pile of sand. It worked great on my vise !
My concern is it better be out of the car to weld on if it’s a newer car with innumerable computer modules. Otherwise grind a super clean area and ground it WELL and CLOSE . Then cross your fingers.


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[FirstEliminator]

The manifold isn't available new. But, there are plenty of used ones. I'd gladly go that route if date codes weren't important. I have a few of those and none are as nice as this one. This manifold is original and has the proper casting and date code. The manifold will be painted and the car isn't a daily driver, so looking rusty isn't going to happen. The attempt is to restore to a concourse state. It's a 1969 Cougar Eliminator that is the lowest vin number of all Eliminators made----like my user name FirstEliminator. It's not a million dollar car, but Cougars done correctly can sell for over 100K. Value is a moot point as I'm an actual enthusiast, not an investor using cars as a commodity. Repairing this manifold is what I feel is the best course for restoration.

Can you define uber-rare, jmho, and Ymmv? I got the original poster acronym. I'm curious, what is your collectible car?

Jmho here, op is obviously welcome to do as he wants...

Unless this is some one of a kind, uber-rare 100 point car, which I doubt since he's said manifolds are available to buy new, then I'd just buy a manifold and be done with it. Ymmv.

Often times, folks go off the rails keeping old crappy parts on a car that's old just because of some wives-tale about 'original parts'. They don't stick serial numbers on exhaust manifolds, and they'll be rusty in no time anyway. And I say this as an owner of a rather collectible car.

[FirstEliminator]

Thanks for the how-to replies. I might have to attempt it on my own as I haven't yet found a shop that this is their forte. I don't want the "well, I'll give it a try..." and have it not go so well. There are guys around me that are very good welders, but no specialist of cast iron.

[FirstEliminator]

The crack is in the up close pic.

[BugHunter]

I had an exhaust manifold on my boat freeze and crack many years ago. I took it to a local shop where I purchase my welding supplies and had the guy there weld it up. He's been around a while, vastly more experienced than myself , especially then. I believe he's in his eighties now. He was reluctant but gave it a shot. He brazed the cracks while keeping a propane rosebud on the thing for a very long time, I want to say hours. Now keep in mind on a boat the manifolds have water going through them so they never get hot. It's a totally different arrangement. They probably only see 160 or 170 degrees. They held up for many years and I'm sure are still on the boat just fine. The drain plugs tricked me when I opened them and nothing came out. Well there was water in there all right.

Imho = in my humble opinion.
Ymmv = your mileage may vary.
Uber rare, imho = very few examples surviving.
Collectible = 60th 427 Convertible (only made 1 year, likely never again 7L car)

[BugHunter]

I was sitting here thinking about how to resurface your manifold when you get it welded. It will need to be very flat before you install it or you will put a lot of stress into the thing and likely break it again.

I have a flywheel grinder at work which has a big flat table and then a probably 13 or 14 in face wheel which you can adjust the height to match the table. In that way you slide the flywheel using your hands over the wheel and very slowly dress the surface. I wonder if something like that wouldn't work on the manifold. If you have an engine shop nearby you might see if they can do something similar to grind the mating surface when you are ready.

[FirstEliminator]

If I have to try it I might. I saw a video of a guy welding a crack on a cylinder head in a BBQ grill like mentioned above.
427? The way you say 7 liter makes it sounds like a Galaxie. Or do you mean Chevrolet?

[FirstEliminator]

I have a 6x18 surface grinder to resurface the manifold. If you meant Ford 427 before, you are probably aware of the long cast headers. I have a set of C5 headers in my 68 wagon that took a lot of flat sanding on 60 grit paper glued down to a drill press table. It was probably still quicker than setting up an exhaust manifold on the surface grinder.

[BugHunter]

Corvette.

I don't mean a surface grinder per se. I have several of those also. The thing I'm talking about, at least the one that I have, think of it like this. Imagine a table at about countertop height with grooves in it all ground and Polished for the purpose of having Parts slide on top of it. It's about four and a half feet wide and let's say 20in deep. In the center of the table there is a hole and within that hole there is a grinding wheel which is self-balancing, with a downdraft fan and is adjustable for height so it matches perfectly to the table itself. So you slide a part around on the table and whatever goes over the wheel gets dusted ever-so-slightly. In the case of a manifold like your V8, you could have the two outside Runners still on the table while just touching the center two with the wheel or you could have three on the table and the end one on the Wheel. Not sure if that makes sense. But you're using the mating surface of the manifold as the reference to the table and whatever High spot or low spot gets hit by the wheel and made Flat.

I looked for a picture online and I couldn't find one.

[FirstEliminator]

I believe Van Norman made a resurfacing grinder like that. A guy in the Albany, NY area had one for sale that I came close to buying, but didn't. I'm long since out of space due to my machine collecting habit. Imagine the game tetris with all the blocks shaped like lathes, mills, grinders, shapers, saws and welders. That is my shop. Now I am trying to determine how to fit a J&L turret lathe.

[BugHunter]

Mine is a "Lempco Model DSM Surface Grinder". Without the brand and model, you can search surface grinder till you're blue in the face and not find a pic. Here's a pic of what mine looks like, except mine is mostly used as work table and all covered up with stuff for adjacent machines. Given your statement about your shop, you probably know what I mean.

[cj737]

Grind a V into the crack. Drill a small hole at the ends to prevent further cracking. Preheat it at 400* to check for any other cracks. Then preheat to 500* and weld it. If you post-heat it, and control cool it, you should be perfectly fine. I don't believe you will need to regrind any manifold surfaces or suffer distortion provided you do the heat-cool thing. Gaskets will accommodate for any surface irregularities anyway. These are vintage cast parts and were never manufactured to flatness tolerances that modern machining can produce.

I'd grab some nickel TIG rods and do it. Worst case, you send it out or redo it later if it doesn't hold up. You can use a 60 grit flap disk afterwards to get a good looking surface followed by some sandpaper and bead blast it if cosmetics concern you.

[clavius]

I don't have much practical experience to share, but if you end up attempting this on your own, maybe it would be valuable to pick up some random old cast iron manifold at a junk yard. You could crack it in a few places and get some practice on that. It would give you some firsthand feel for how difficult (or not) it is for you to do, without risking something you can't easily replace. It will either be a great confidence builder or a flag that you would be better off farming out to a specialist.

Whatever you end up doing, I hope you will post a follow up here. It's always interesting to hear how things work out.

[Camaro77]

is this cast iron or cast steel? I would V that crack out preheat it with a torch weld it up wrap when done to cool slow and feather the weld area. tig it with a nickel rod like 312 and dont worry about it.

[cwby]

Hey guys,
The repair I am looking for needs to be not visible.
What would be the best course of repair for this?
thank you,
Mark

Might be a good solution - The DHC Cobra torch is a niche tool. but plenty cool for some uses.

https://youtu.be/CorPYHHOpus