Block Welding Question

Discussion in 'General Chevy & GM Tech Questions' started by 85 S10 Man, Aug 16, 2012.

  1. 85 S10 Man

    85 S10 Man Member

    i just bought a used 2.5L engine out of a 91 S10 to put in my 1985 S10 because the engine started mixing water and oil together.

    Well anyway i bought this other engine with less then a 100,000 miles on it and i got to cleaning it up today and found the block had about a 5 to 6 crack in it.

    It is right under the 3 freeze out plugs on the left hand side.

    Well my question is can i take a stick welder or a wire feeder welder and weld it the block where it won't leak coolant out?

    I had a few mechanic guys tell me that i can do it and then had a few tell me it wouldn't hold and bust back loose with a bigger hole.

    I'm a pretty good welder and i think i can do it but i really like to know if i can do it or not before i try.
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    It's not recommended, I've never seen one last, cast items dont take a good weld and will almost always break on a weld after a few hot and cold cycles.
  3. 85 S10 Man

    85 S10 Man Member

    oh i c well you think i can have the crack brazed? I'll try to get some pictures on the crack later on today when i get off from work and stuff.
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Even with brazing your facing the same issue, normally a cracked block is done, no way to reliably revive it.
  5. 85 S10 Man

    85 S10 Man Member

    oh i c well i'm on the hunt again for a 2.5L S10 engine i guess
  6. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    I would respectfully disagree with tbplus10. Cast iron is welded all the time with good results and this includes blocks and heads. Now having said that, there are times and places that it would not be prudent. I think in your case if it is an external crack in the water jacket and and does not involve the machined plug holes then I would give it a try. Prep well and go for it after some self education on the subject.
  7. 85 S10 Man

    85 S10 Man Member

    Oh i c well i done sold it to a other feller that needed the head off of it. What i should have done is waited until i found out more about welding cast iron before i got rid of it.
    Last edited: Aug 17, 2012
  8. 85 S10 Man

    85 S10 Man Member

    hey i bought it back and i am wondering how much nickel do i need in a welding electrode rod do i need to weld cast iron?

    I can get some rods with 55% nickel but i don't know if that will be enough to weld to hold.
  9. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    The shops that will weld cast iron will have some means to heat the casting and hold the heat in so as not to cool to quick. You will need to be able to this also. I was fortunate to have had access to a large kiln used in the local art class for some projects and used our stove at home set on self clean (I think about 500 deg.) for smaller peices. Can't remember what rod I used, the one recomended by the local welding supply (15 years ago). Repaired a few of the old "hit and miss" farm motors that had been left out to collect water and freeze. You will have to get creative to heat it up, maybe a couple of turkey frier burners under it while on an engine stand, weld it and cover with some insulation to slow the cooling. One of the bennifits to this is that if yo u keep it at around 450 t0 600 deg for a couple of hours all the paint and gunk pretty much turns to dust. yeah it is a lot of work but it works. Be sure to use some type of crack detector like the dye and developer to make SURE you get to the ends of the crack, it is almost certain to go past what is visable to the naked eye. I have been successful but I have sought the advice of WAY more experienced people than I to help me out. Check out some you tube videos about welding cast iron to see what is involved.

    P.S. When the art director found out we were heating "greasy" things, that little perk came to a screaming halt. LOL!
  10. giorge

    giorge Rockstar 100 Posts

    When you are preheating you want about 1200 deg. 500 is not enough.
    55% rod is what I used and there is another rod that works really well it is called Certanium 889S. You need to V grind the crack and if the crack is in an area that has a lot of stress on it I will drill a small hole at each end of the crack before grinding it. You also have to make sure there is no grease otherwise your weld will not hold. If you are going to use stainlesss wire feed a 110v wire feed will not work, it won't go hot enough. Make sure you peen it for quite a while after you weld it, otherwise it might crack or break. I have a small ball peen hammer that I use.
    for reference when using the 1/8" nickle rod you should have your welder set no lower than 125 amps.

    I hope this helps.

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