[TheNovaMan]

Hi guys, I have a big block Chevy with two cracks at the outer bolt hole of the starter mounting ear. Here are a few pics. (Note that the cracks go farther than it appears in the pics.)







The block is at the machine shop being checked for other cracks. When I get it back, assuming it doesn't have more terminal cracks, I'll stop drill the cracks, vee them out most of the way with a carbide burr, and thoroughly solvent rinse the cracks and bolt hole.
I have a 170A MIG welder and an AC225 buzz box. What's my best bet for a repair that won't crack again?

[Coldman]

Your 170mig lacks grunt.
Personally I would not stick weld this repair.
Your best bet is to tig it up.


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[Coldman]

Stick welding with a nickel rod is an option worth considering


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[TheNovaMan]

I've been doing a LOT of reading on cast iron welding, much of it here, and these are what I figure my main options are as far as doing it myself.

Buzz box
Medium nickel rod, like nickel 55
High nickel rod, like nickel 99
Muggy Weld 77

MIG welder
Weld with medium nickel wire, like Crown 44-30 (takes 24V, which my welder probably doesn't have)
Weld with high nickel wire, like Crown 11-30 (takes 17-20V, which I bet my welder can manage)
Braze with silicon bronze wire
Braze with aluminum bronze wire

Is there a way I can measure the max voltage of my MIG machine? Can I just put a voltmeter on the tip and the ground, pull the trigger and measure?

[MFleet]

I have been able to observe a tiny amount of work from a casting repair specialist. The casting stays insulated during pre-heat and work. It is then completely covered for post-heat. Sometimes they sit for several hours or overnight if it is late in the day. I can confirm that a buzz box and nickel rod is used for certain procedures. There is no mig machine anywhere in that shop, but there is an O/A rig.

[MFleet]

Odd that I had a call on what appears to be the same hole (small block) shortly after I posted. I was able to get a bit more information on it

No pre-heat is required for this type of repair with stick.
Keep a large area or entire block insulated and covered high temp blankets, wadding, etc. Leave just the work area exposed.
Make short passes. ~1/2 of a stick per cycle to prevent overheating. Terminate the work before the block gets too hot to touch.
Cover work area with more insulating material and let it cool 45min-1hr.
Repeat the process to completion, cover, and give it plenty of final cooling time.

The stick recommended is 3/32 designed for oil soaked castings. Look up the price on "mg289" or similar offerings and feel your jaw on the floor I may have a lead on a very high quality stick for half as much as mg289. The down side is that I will need to order twice as much.

In my case the piece cracked....and then it went missing. This is going to be a slightly different procedure obviously. We both had to drop the call before I could work your particular repair into the conversation.

I will post up If I can gather more info. Hope some of this helps and good luck!

[TheNovaMan]

Thanks for the additional info, Fleet. I think we've both decided to do essentially the same thing. I emailed Crown Alloys to see what they recommended, and after clarifying a couple things with them, I had my LWS order me a pound of Crown's Royal 260 rod in 3/32" diameter. As far as I can tell, it's virtually identical to Messer's MG 289 - they're medium nickel rods with flux designed for dirty cast iron. I don't really understand how this can be, but medium nickel rods produce a stronger AND more ductile weld deposit than high nickel rods. I think this is one of the keys to a successful cast iron repair - as the cast iron cools and shrinks away from the weld, the weld has to have enough give to it that it won't crack at the toe. I figure that's also why peening the weld helps.

As far as cost, yes, they're expensive compared to regular stick electrodes. My wallet will be $53 lighter once I go get my rods, but nickel is expensive, and welding cast iron is a niche application. For every pound of these rods sold, there are probably thousands of pounds of regular rods sold. But, if it works, it sure beats buying another $500+ used block!

As far as procedure, I'll start by cleaning the bolt hole as well as possible, stop drill the cracks, and vee them out. Fleet, I like your idea of extensively insulating the workpiece. I think I'll buy a few batts of fiberglass insulation, stuff the block full, and then wrap it. Crown says "warming to 400°F to 500°F will produce a softer weld and minimize stresses on heavier sections." I plan to buy a 400°F Tempilstik to verify my warming. Weld a small section, peen, cover, let it slowly cool below 400°F, then repeat.

One more question: with a crack that's stop drilled at one end and unrestrained at the other end, where do I start welding, and where do I weld next?

[MFleet]

See if this

One more question: with a crack that's stop drilled at one end and unrestrained at the other end, where do I start welding, and where do I weld next?

I sent a picture of what you have and hopefully I talk to him again in the near future. Logic tells me to start with a small amount of material at the stops to reinforce the intact material. Then start a first pass towards the machined surface.

Good call on stuffing the block. He did mention that insulation should be added on the inside near the work.

Does this look familiar?
http://www.hotrod.com/articles/ccrp-111 ... cast-iron/ Load the pictures and read the information at the bottom of each picture.

[TheNovaMan]

Wow, great find - that's virtually identical to my situation!!! Even the clocking of the cracks is dead on! There are only three differences, none of which matter:
1. My block is not numbers matching
2. My block is a 454, not a 396 (both are big blocks)
3. My block is a 4-bolt main, not a 2-bolt main