Welding Cast Iron Exhaust Manifolds

[qwik240z]

I am trying to use Cast Iron exhaust manifolds on my LS1 240Z project. The stock Camaro manifolds won't fit but I picked up a set of Hummer H2 manifolds and with some modifications they seem like they can be made to fit. The drivers side flange might just need to be trimmed a bit where it is hitting the frame and the original flange should work. The passenger side is way too tight to fit. I need to cut off the flange and weld a piece of steel exhaust pipe to it. I was told to try to press fit a steel exhaust pipe into the cast manifold and then have it welded around the seam.

 

I am getting mixed opinions on welding cast iron. Some say yes, some say it won't hold.

 

Anyone have any experience in this?

 

Also, anyone know about this stuff?

 

http://www.muggyweld.com/castiron.html

 

Thanks!

[Mike kZ]

I have heard of that muggyweld, but have never used it. Here are some other ideas ,hope they help: http://www.enginads.com/extras/2003stor.cgi/noframes/read/49078&expand/1

[johnc]

Some cast steels are very weldable with the proper technique. There are four main types of cast steel:

 

Grey Iron - very high carbon and some free graphite - weldable.

White Iron - very high carbon with a cementite granular structure - not weldable.

Nodular Iron - same as grey iron with magnesium or silicon added for ductility - weldable.

Malleable Iron - reheated and processed (annealed) white iron - weldable.

 

You exhaust manifold is most likely Nodular Iron. There are two ways to weld it:

 

1. Pre-heat to 600-1200F.

2. Stick weld it using an ECI or an ENI rod. TIG weld it using 308L filler. MIG weld it using ER70S-6 filler.

3. Skip weld using 1" beads and peen each weld with a sharp pointed hammer as the bead cools.

4. Maintain interpass temperature above 600F.

5. After welding the part must be cooled slowly (over an 8 hour period) to room temperature. Bury it in deep lime or dry sand, put it in an oven set at 500F, or fire up the grill.

 

Another way:

 

1. No pre-heat.

2. Stick weld it using an ECI or an ENI rod. TIG weld it using 308L filler. MIG weld it using ER70S-6 filler.

3. Skip weld using 1" beads and peen each weld with a sharp pointed hammer as the bead cools.

4. Make sure the part doesn't get any hotter then 250F except immediately around the weld you just finished. Be prepared to stop welding for a 1/2 hour at a time to let the part cool.

[Clifton]

I've welded (mig) on Toyota and Nissan manifolds but never domestic stuff. I tried weldeing a GEO manifold but it wouldn't have anything to do with it. I would try laying a bead on the back before cutting it up. On the last Toyota one I did I had one weld crack at the manifold when cooling. I preheated it before I went any further. I didn't have any problems. I just let it cool naturally. 105* air temp helps to I think.

 

Clifton

[ToplessZ]

I think if I were to do this I would go the gas welding route. Either way make sure to get good penetration which is harder when welding on cast. This will prevent cracking. Im interested in the muggy weld stuff myself sounds a little good to be true. Basically looks like a brazing technique but I wish someone else would chime in on that.

[johnc]

Either way make sure to get good penetration which is harder when welding on cast.

 

Not true when welding cast steels. Too much penetration draws carbon out of the base metal into the weld and makes the weld brittle. You want the weld as ductile as possible to prevent cracking and you don't want to draw carbon into the HAZ.

[waynekarnes]

my 240, using the scarab kit, has the cast iron rams horn exhaust manifolds, with air injection ( smog legal ).

 

to clear the steering shaft, the lower portion of the manifold was cut off, tilted and welded back on.

 

i did not do the welding, i was told my friend's uncle did the welding, he installed the V8 into the 72, back in '77, in his driveway and his garage. the weld is solid ( i had to drop the exhaust pipes, when i pulled the heads, i was turning so hard on the bolts at the bottom of the manifolds, to get the pipes free, i was rocking the car. 27 years and the weld holds strong ).

 

so, the answer is ... if you know what you are doing, cast iron manifolds can be welded and last as long as the rest of the manifold.

 

wayne

[jgkurz]

Some cast steels are very weldable with the proper technique. There are four main types of cast steel:

 

Grey Iron - very high carbon and some free graphite - weldable.

White Iron - very high carbon with a cementite granular structure - not weldable.

Nodular Iron - same as grey iron with magnesium or silicon added for ductility - weldable.

Malleable Iron - reheated and processed (annealed) white iron - weldable.

 

 

Just for future reference, does anyone know which type the Nissan L28ET manifolds are?

[Clifton]

L28ET is very weldable with MIG. I have some pics on my link of mine with a T4 flange and external wastegate.

[jgkurz]

L28ET is very weldable with MIG. I have some pics on my link of mine with a T4 flange and external wastegate.

 

Do you know which one of JohnC's recommended method's would be preferred?

[johnc]

First method, starting with the part over 600F, keeping it over 600F during the welding process, weld it using Stainless 308L filler, and slow post-cool down over 8 hours back to room temperarature.

[Clifton]

L28ET is very weldable with MIG. I have some pics on my link of mine with a T4 flange and external wastegate.

 

Do you know which one of JohnC's recommended method's would be preferred?

 

I used ER70S-6. There are pics of the 3 I've done, 3VZE Truck, 7MGTE Z and L28 Z scattered in my Yahoo folder.

[Drftn280zxt]

they are very weldable. For my exhuast being done by "pros" at the muffler shop they just welded the pipe right to the exhuast manifold with MIG. Next time in the future , I'll have flanges made to work with custom headers as well as mandrel bends versus crushed bends.

[Dan B]

If you have a tig machine, go over the weld many times without adding any filler rod. When you do this you will see some black stuff come out. This is contamination, that causes the weld to crack. After each pass clean this off, and when it stops coming out you should be good to weld it

[ozzzzz]

First method, starting with the part over 600F, keeping it over 600F during the welding process, weld it using Stainless 308L filler, and slow post-cool down over 8 hours back to room temperarature.

 

First method using a high nickel rod /arc welding would be best.The stainless rod is good too. Also do not use a abrasive grinder on cast iron before welding it. This will smear the graphite casing poor results. Use a file or carbide burr or HSS burr. Wire wheels are ok. To increase penetration without adding more heat you should vee out the edges(chamfer) or add a small gap between parts. The slow post cool down is critical. The high nickel rod is going to be the most forgiving due to its ability to stretch during cooling. The steel and cast iron are going to contract at different rates during the cooling process. Handling 600deg metal is not fun. Make sure you have a spare set of hands to help and they are wearing the proper safety equipment . 600deg will melt flesh like butter.

 

You should use the least amount of heat when welding it cold. Skip welding and peening as John said. Back welding is another method. I have welded a few VW exhaust manifolds with E70s6 with good results.

Edited July 18, 2010 by ozzzzz