Cracked cylinder head. Stitching pins and new seats

[scsmith42]

Years ago I owned an automotive machine shop and worked on a lot of heads - including welding them up and reprofiling combustion chambers and ports.

The advice from others in this thread is valid. Diesel engines have extremely high compression ratios and also internal harmonics due to the combustion process. To properly repair that head, it needs have both pre and post heat after the repair is made. As I recall, post heat is a 24 hour process.

If the tractor means that much to you, drop the grand in the properly repaired head, or better yet contact the repair shop referred to by Garwood above.

Best of success to you.

 

[john.k]

I would not spend 10 bucks on a 'repaired head'.....because its likely a monumental bodge done by ripoff merchants.........the only 'repaired' heads that work are done by cutting out the entire cylinder top,replacing with a new made part ,welding the joint (which is outside the pressure area),and sealing the intake and exhaust passages by using long valve seats.........KC s used this method on GM 71 and 92 series diesels.........others used the same method on big Caterpillar heads .........Cats are all direct injection now ,so the heads dont crack .

 

[Wlhequipment]

I decided to weld it, and if that fails, I’ll buy the junkyard head. I bought a box of nickel rods (for 100 bucks wow), and I’m going to use my grill for pre and post heating. Then all I have to do is re-grind the valve seats and maybe it’ll work, maybe not.

 

[gbent]

Please let us know how it works out. Personally, I would buy the junkyard head now, while it is still available. Then if the repair works I'd sell the replacement.

 

[cg285]

i've welded a shit load of cast iron exh manifolds over the years with o/a and complete success. you get no penetration on the cast iron so the crack needs to be "U'd" not V'd to avoid stress
i always used a rose bud for pre and post heat. certainly not 24 hours. maybe 24 minutes. your head however is much larger

 

[PackardV8]

I decided to weld it, and if that fails, I’ll buy the junkyard head. I bought a box of nickel rods (for 100 bucks wow), and I’m going to use my grill for pre and post heating. Then all I have to do is re-grind the valve seats and maybe it’ll work, maybe not.

You'll need a really large, really stout grill to pre-heat a diesel cylinder head. Will the cover on your grill close over the head?

jack vines

 

[Wlhequipment]

It's a 2 cylinder. It's maybe 8" x 10" by maybe 3" thick. My grill, incidentally is cast iron also. So it retains heat pretty well.

 

[Wlhequipment]

I'm learning the ins and outs.

 

[gbent]

You need flux to gas weld cast iron.

 

[eKretz]

I decided to weld it, and if that fails, I’ll buy the junkyard head. I bought a box of nickel rods (for 100 bucks wow), and I’m going to use my grill for pre and post heating. Then all I have to do is re-grind the valve seats and maybe it’ll work, maybe not.

You'll need to recut the head flat also.

 

[cg285]

You need flux to gas weld cast iron.

welding supply stores should have cast iron rods (and flux)

 

[Wlhequipment]

You need flux to gas weld cast iron.

Hah! Well that’s probably why it went so badly

 

[Wlhequipment]

The head is already in the …”kiln”… I’ll leave it in there for a couple hours, weld it, then stick it in a bucket of sand. I was going to just turn down the grill a little every hour, but I got too much to do today. Yesterday I made a plate out of 1/2” that I can use to bolt up to the head and pressure test it, after the weld. We’ll see what kind of warpage happens as well.

 

[Wlhequipment]

I tried to take a pic, but it didn’t post, and I’m not going to spend time figuring out why. In any case, I peeked at it a couple hours in, and it looks like maybe it’s getting moisture baked out of it, because what was shiny metal now has a slightly rust look to it. Ill have to take a Dremel to it again before I weld. Also, I noticed when it’s hot, the crack is invisible. I didn’t expect that much expansion movement in the material. If it moves enough for my blind eyes to see it cold and not see it hot, I’m thinking for sure this crack will return.

 

[eKretz]

Not necessarily. The material is far more ductile while it's hot. That's why you absolutely need to SLOW cool it, so that it can give a little as it comes down in temperature. You need to keep it hot while welding also. This isn't likely to work well if you put it in a grill, then take it out to weld, then put it back in a grill to slow cool. I always keep a torch on the work while welding if it's not a very substantial piece. You might want to try welding in the grill with the heat still on. And you can try to keep the part in the grill to slow cool, but at bare minimum, wrap it in something like an insulating blanket (after the fire is out...) or put it in a metal tub of sand that has been preheated in the grill.

 

[cg285]

DO NOT grind with any kind of abrasive. a chisel is actually a recommended way

 

[gbent]

You will have to install valve seats after welding, the filler is unsuitable as a valve seat.

 

[Garwood]

You will have to install valve seats after welding, the filler is unsuitable as a valve seat.

I was wondering if the OP was going to discuss what he was going to do for seats. Seams to have skipped right over that part. This sure seems like a great way to spend money and time and not get a useful result. I'm suspicious the purpose is not to get a working cylinder head, but drum up some Youtube views.

OP- nickel rod welding cast iron has it's place in some repairs, but I think you'll find you are tackling a repair that is not suited for nickel rod.

IME, nickel is a very bad choice where the repair is central. It's good to reattach an ear or a small flange. If you try to build up nickel in the middle of a large part it doesn't work well. Nickel is also really bad for anything you need to post-repair machine. The HAZ from nickel welding is as hard as carbide. It is carbide. So welding on this head, through the valve seats, means you'll have to machine pockets for hard seats through the nickel and through the HAZ.

My cast iron repair decision tree goes something like-

1) Buy a new one

2) Oxy/acetylene braze

3) remake entire part from steel machine from solid/weldment

4) Have Diesel Cast West repair the part using their furnace TIG welding process.

5) Maybe consider nickel rod, but probably just decline the job if nickel is the route the customer wants. nickel looks like shit, makes the part impossible to machine and just never seams to be a reliable repair method. Sometimes it holds, sometimes it looks OK, but cracks propagate elsewhere in the part. I've found that a lot of cast iron is nodular grade and at elevated temps it will weld rather nicely with standard old 70 series MIG wire. I've repaired dozens of CAT, Cummins and IH turbodiesel exhaust manifolds and windowed engine blocks with preheat and MIG wire.

 

[john.k]

Back in the day when hillbillys owned old broken bulldozers ,it was reckoned to weld cast cylinder heads,you either arc welded in spots never letting the head get hot so you couldnt put your hand on it.....alternative was to heat the head red hot and gas weld using broken piston rings as filler ..............here is a bit of good advice......cast iron is very fluid melted ......if a piece is heated to melting heat ,it will run away like water...........so ,the weld needs to be supported with a moulding sand or the like

 

[eKretz]

I never had trouble machining nickel rod on cast iron as long as the heat was done correctly. You want it VERY hot, closer to 800° works good. Kept hot while welding and slow cooled (slow like over 12 hours minimum), just like any other weld on iron. I did an unobtainium dump truck wheel hub with Ni99 last year, cut beautifully. Someone had put the wheel on but must not have had it seated correctly and it came loose while the dump was fully loaded with chipped wood from a tree service. Roached the hell out of the hub. I welded up all the eroded areas and remachined everything afterward; went great. Good heat is key regardless. The hotter the better IMO. And I've repaired countless iron connecting rods from punch presses up to 350+ ton with nickel rod. Nary a problem.

We've had this discussion here before about whether iron can be "cold" stitch welded. I have done it with no issues but be sure to peen the hell out of it, and you better hope you don't need to do any machining of THAT interface or weld. It will probably also be brittle as hell, won't take impacts well.