cracked block

[Brew]

Cool site, guys! There sure are alot of Pontiac folks here!
I've got a small problem. One of my cast iron engine blocks is cracked, and I'd like to fix it instead of replace it. The crack is in the water jacket, so the area wont see alot of pressure (unlike say a main bearing saddle or something), just whatever 180 degree antifreeze exerts on it.
I saw on HotRod TV (or something similar) a guy "cold welding" on cast stuff, using nickel rod and just laying good tacks, then letting the area cool entirely before proceeding.
Does this sound like a good idea to you?
If not, what are the alternatives? BTW, I dont have the capacity to pre-heat the entire block, but I'd really like to fix this myself.
Thanks for the input.

[mikemilburn]

Hi all, figured I'd stop lurking and post something. I've welded a fair bit of cast in my time using a Ni-Rod, the theory is to keep it cool to the touch, hense the reason for using short beads. The best way to do it is to V out the area slightly and lay short beads not allowing the area to get too hot to touch. Between passes, peen the area lightly with a chipping hammer or some other semi-pointed instrument, this releaves the stresses. Be advised, any cast rod I've used is not usable on an AC machine so judge youself accordingly, there may be AC rods out there, I'm not sure. As another note, it's not always a sure thing, castings range from good to pure crap so you could be wasting your time. Good luck and let us know what happens....Mike

[Brew]

Thanks Mike. What do you think of using a Tig machine instead of an arc welder?

[Guest]

Originally posted by Brew
Thanks Mike. What do you think of using a Tig machine instead of an arc welder?

That would be my weapon of choice....I have heliarced cast iron with good success using Certanium 889 stick rod, by removing the flux, first. There are probably a lot of other ni-rods you could use also. Prep the surface good...no oil or grease...if you can grind out the area to weld, do it. Stop drill at the crack ends. Then weld an inch at a time...try to keep the interpass temp cool around 300 or so, and you should be oK.

[Pin Head]

I know that this is a welding site, but I would pin this type of crack with C type pins. It is kind of a PITA, but once you get the hang of it, it goes pretty fast.
Check it out:

Stitching pins

[Brew]

PinHead, great site with lots of good info! Definate bookmark! Thanks!
But, alas, I'm a weldor, so I'm alot more comfortable sticking with what I know. My main concerns are not whether it will be sealed or whether the crack will be contained, but whether this type of repair will stand up to the constant heating and cooling that engines see in their life cycle. And the fact that to make this a working motor again is going to require $1000.00+ in machine work, and I cant afford to lose that kind of dough if the weld fails.
Bottom line question: does anyone think that a welded crack will NOT stand up to expansion and contraction on a regular basis?
Thanks for your knowledge!

[Pin Head]

I can't comment on whether welds might ultimately crack because I have always pined this type of crack. Since you are planning on spending over $1000 on machine work on this block anyway, why not have your machine shop pin the crack? They do this stuff routinely and I would imagine that it would run $25-100 depending on how long it is.

[mikemilburn]

IMHO I wouldn't attempt to repair the block, putting out $1000 and then having anti-freeze puddle on the floor isn't my idea of a good time, again it's just my 2 cents worth.
As far as tig goes I've never used it on cast, much of a technique involved Rock?...Mike

[Hobart Expert Rock]

HI MIKEMILBURN..............AH YOUR IN LUCK........... I HAVE ASKED CHRIS FROM THE R & D LAB TO ANSWER THIS ONE.........SHE IS GOING TO ANSWER ANOTHER ONE TODAY ON WELDING PROCESSES FOR ME.................JUST TALKED TO HER SO LOOK FOR HER ANSWER SOON (TODAY)....... I THINK SHE IS WRITING A STORY FOR ME AS SOON AS IT'S DONE YOU WILL GET THE SKINNY.....................................ROCK... .......
[email protected]

[Mike Sherman]

Brew, the process you saw on TV will work. I personally don't use it. You can do this job with an ESt electrode if no machining is needed or ENi if you are doing machining (casting must be very clean for this electrode). You can preheat the area with a torch to 500 to 900 degrees F. and try to maintain this for the duration of the welding. Slow cooling of the area is important with this process. Using short welds and keeping the casting cool while peening the short welds is the process you saw on TV, and as I said it will work, I just don't like it. I also use a powder flame spray system that requires no preheat and no postheat. It is very nice system for low pressure applications. Good luck and keep us posted.

[Ed Heimbach]

Get some 3/32 MG 289 wire, and follow all the good advise you see here, and you should be able to get a leak-free block.
I've used this rod to weld some nasty cracks on all kinds of cast, and I have had no problems.

[Brew]

Thanks for all the great input guys!
I vee'd out the crack, and cold welded it with nickle rod and ~95 amps heliarc, stress relieving it after each "tack". It looks pretty good, porosity was at a minimum, and the surrounding material never got too hot to touch. I hope to have it mag'd and pressure checked before this summer (its really a spare block, I dont need it right away), but the true test will be quite some time down the road.
Thanks again!
John