SBC freeze crack

[Dragsinger]

This is a new happening for me. In the past I would delegate this to scrap. Now that 350 four bolt blocks are becoming harder to find, can a successful repair be accomplished on this? Everything else looks normal and the deck is flat.

[barnym17]

loc&stitch repair kit will fix it.

[bill jones]

Brazing a cast iron crack
-I do NOT care for cast iron welding of the block, but instead I would braze the crack.
-That needs to be done by somebody who KNOWS what they are doing.
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-When blocks are cast iron welded they heat the block so bad that the block comes back red in color and I don't like it one bit.
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-To braze the crack I drill a hole 3/16" hole at each end of the crack, then I use a 3/8" diameter carbide burr ball and I dig out a trough the full length of the crack until there’s a 1/8" gap at the bottom of the trough.
-Then I take a 1/8" ball burr and cut thru that gap and try to clean up the water jacket side slightly.
-Then with two people and two torches, you preheat the block for a short time and then you concentrate one torch on the side you intend to braze and use the other torch to braze the trough.
-I use 300 and a 350 degree F temperature crayons and when the block is 350 degrees several inches inches away from the wound and 300 degrees say 6" from the wound I start to braze.
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-I start at one end of the trough and braze it a short distant, back off for a moment and wave the other torch around to spread the heat out, then I'll start at the other end and braze it a short distance, and do this same procedure several times until the wound is filled.
-I don't like to braze more than about half an inch at a time because you end up with too much concentrated heat at the wound.
-I like to back off momentarily and let that heat spread out with some help from the second torch.
-Then when you have trough filled and finished you have to back down on the heat but continue to apply some declining heat thruout the block for maybe another 10 minutes and then cover the block with blanket to hold what heat you have in there.
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-I also use an air hammer with air pressure regulated down and I'd either use a needle descaler tool or I have a chisel end that I have prepared that has some teeth, that I use to lightly air hammer or peen the wound and out and away from the wound as the cast iron is cooling off, lightly working this air hammer during the 10 minutes of declining heat, maybe even until I could almost touch the block without getting seriously burned.
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-I have done several blocks this way and none have cracked during the cool down process and none have leaked water.
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[BillK]

Are you absolutely certain that it is a crack ? Have you magnafluxed it ? I have seen more than one SBC block over the years that looked like that but it turned out to just be a casting mark. Grind it smooth and magnaflux it to be sure.

That being said if it is a crack then Loc-n-stitch C2 pins will fix it.

[barnym17]

Loc and stitch is pretty easy just drilling,tapping and a little grinding,The pins threads are designed to actually pull the crack back together as they are installed.

[vortecpro]

This is a new happening for me. In the past I would delegate this to scrap. Now that 350 four bolt blocks are becoming harder to find, can a successful repair be accomplished on this? Everything else looks normal and the deck is flat.

Virgin 350 blocks are available on Facebook marketplace IF you can stand text messaging people your trying to do business with and waiting for a reply.

[Paul Kane]

The location of the alleged crack makes for an incredibly simple stitch repair, and could even be corrected with Irontites if you wanted.

Given all the technological advancements we have today compared to decades ago, the welding of cast iron should be considered a "Plan B" to stitching, and utilized only when stitching isn't feasible under the circumstances.

Brazing is a patch repair, in effect. Actual welding changes the molecular structure of the cast iron and makes it brittle. A proper stitch repair will not only eliminate the crack but it will also be literally stronger than the original casting.

Stitch01.jpg

Stitch02.jpg

Stitch03.jpg

Stitch04.jpg

Stitch05.jpg

Stitch06.jpg

The very last image is after the crack repair was textured with a needle scaler, after which it will patina like the rest of the block. Oilah, that crack is gone!

[Dragsinger]

Thank you to all for the help and advice. It is for sure cracked. To be positive, I used a small bur and ground slightly below level. This situation is a good example of "first impression is many times correct." After reading the comments about "are you sure? might be casting flash" Each time I would walk by and look it over I would think, "well, maybe, could be, although it is in an unusual place." My first impression was correct.


For the short term this block will be stored under a bench while looking for another block. And maybe use for mockup with the S-10 I have under construction.

[KnightEngines]

Lock n stitch, permanent & strong if done right.
That's an easy fix.

[BOOT]

Splayed main a 2 bolt block

[rfoll]

I had a pair of cracks just like the one pictured. The engine is a Vortec 350 I built for my Impala. After the break in and initial oil change I left it on the test stand and took a Christmas vacation in Hawaii. When we got home 10 days later the high temperatures were in the 20s. I remember someone telling me it doesn't get cold in Oregon. When the monsoons returned and the temps went up into the 50s I found a big puddle on the shop floor. Seems I didn't think to drain the block. Cracks bigger than your pictures on both sides and straight through both drain bungs. Did the locknstitch thing and have not had any leakage at all. It's been over 10 years. A note to all thinking about using this method, the taps are very fragile and expensive.