Cracked manifold fix?

[vacca rabite]

So it looks like my manifold is cracked in three places.

Short of buying a new one, can I weld the cracks up on the one that I have? I have a MIG welder.

Zach

[randyscycle]

Cast iron behaves very differently than steel when welding. There are a lot of camps on what is best for repairing it. Most likely if you do MIG weld it, it will crack again, either in the same spot, or near the repair.

Generally the old way to weld cast was with an arc welder and high nickel-content rods. You preheated the cast first and then welded it and allowed it to cool by itself. This was OK, but, it wasn't exact science as you didn't really know how hot you were preheating to, and couldn't maintain an constant temperature.

TIG is the best method now for cast welding. It keeps the heat concentrated at the area of repair. You can also choose exactly the correct filler rod for the job, although what was used to cast your manifold is anyone's guess.

Replacing it would be your best option overall.....

[vacca rabite]

I was wondering if anyuone had tried this:
http://www.muggyweld.com/castiron.html

Looks like it could be promising, though my manifold might be to far gond to try welding. Looks like my ears are totally cracked off.

Zach

[Jay Dog]

Hey guys, just wanted to throw in my 2 bits. Yup! cast iron can be a tough one to work with. I have had good results with Stick, Tig, and Oxy-Fuel welding. I have never used the Muggyweld rods, but I bet they are similar to Certanium rods. I have used these with success.

http://webapp1.cronatronwelding.com/...temNum=P+12003

These are really easy to use and lay-up material well for filling large areas where a deep crack may have been ground out or building up an area. They run smooth and restart easy like hardfacing rods. Use it in short stringers or spot weld it for small areas. Remove slag before going back over as you fill or you will have porosity. When finished or machined it will match the parent metal almost identically.

The TIG process will work if you have access to a machine. DCEN and low heat/amps. When TIG welding the upmost concern has to be heat concentration. The one thing that cast iron will not like is the one thing TIG is good at...A ton of heat in a small area and fast. It is the heat differential or more importantly the expansion/contraction rates from this heat that will cause excess internal stress = crack. With the right amount of pre and post heat (I'll come back to this) TIG will work great as it is much cleaner than stick welding. As Randy stated there are plenty of filler metals available for specific purposes. As for stick or tig, whatever your local welding supply shop has available will most likely be the main factor.

Another option is Oxygen - Acetylene welding. This process has a couple of benefits for the do-it-yourselfer when dealing with cast iron. You are going to have to preheat the poop out the manifold meaning you will already have access to the oxy/fuel set up. Brazing rod takes to cast iron nicely and can be built up well with patience and practice. There are a few fillers made just for cast iron, but standard flux coated brazing rod can be used. The tensile strength of most brazing rods will be close to that of the casting. These rods will typically have a lower melting point meaning temperatures will be kept to a minimum / just hot enough to allow the cast iron to accept the filler. This process goes slow and will keep the heat spread through the part keeping the crack factor down. The down side is that the finished product will not look as nice as the stick/TIG welded part...kinda like a golden seagull dive bombed it.

As with any welding repair prep to the part is important. Cracks must be ground to their root. Broken parts must be grooved to allow filler metals to penetrate all the way through. Parts will pull in the direction that filler metal is applied as it cools. This will be a problem when welding on broken ears or tabs as close attention needs to be paid to alignment. If possible groove on booth sides (double v-groove) and alternate welding on both sides of the part. If the crack is in the middle of the part holes may be drilled at opposite ends of the cracks to help prevent spreading before grinding/welding.

By far the most problematic issue is heat control. Find a location to do your work that is free from breezes of cold air. Preheat, Interpass, and Post heat are all necessary. There is a ton of info on the internet regarding welding temperature requirements for cast iron. If you plan on working within temp. ranges pick up a Temp Stick at your welding supplier. These are sticks with a plastic looking insert that melts when touched to a part at or above a certain temperature. If working without one, the general rule is to use a rose bud torch tip and heat the entire part inside and out...when you think its hot enough...heat it some more! When welding it is important to work the heat through the part between welding passes as it will be cooling on one side as you are welding on the other. When finished welding reheat the part entirely. If the part cracks in the weld the part is not hot enough prior to welding. If the part cracks anywhere else it was cooled to fast.

When finished this last step has to be the most important for cast iron repairs regardless of welding process or filler metal. If cast iron is going to crack, it will crack when cooling. Its evidence will be heard in the form of a ear chilling "TINK". You need to allow the part to cool as slowly as possible. In industry parts are cooled as they are put into ovens with extremely high temperatures which are slowly lowered for up to 24 hours. This can be simulated at home by making a sand box or digging a pit in the yard in which you will cover/bury the part with sand. Your local playground or beach can be be a good supply, but watch out for cat mess. Put down at least 6 inches, lay the part on the sand and cover with at least 6 more. The more sand the better. Let cool for a day. The sand will keep the part warm for hours and keep the elements from it.

There is a ton of info on the web written by guys that have more experience / technical backgrounds on this subject. Find as much info you can before jumping in. These are just suggestions from my own experience. My general saying to pass on to people when they bring in cast iron for repair and ask if I can fix it, "If its already junk, at worst, I can't make junk any more junk than junk already is!"

Have fun with it, post some pics, and Good Luck, Jay

[gimpyrobb]

www.weldingweb.com
or
www.metalmeet.com