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Technical Is my block junk? Freeze crack.....

Discussion in 'The Hokey Ass Message Board' started by RMR&C, May 12, 2019.

  1. Pulled my avatar coupe out of winter storage the other day and noticed a small puddle of coolant under the engine. Figured it was a minor leak somewhere. After some looking, found a 3 inch crack in the side of the block about a 1/2" below the deck.
    Looks like a freeze crack? It was in an unheated building and the coolant tested to -20. It did get that cold here over winter...
    Anyway, I was wondering how bad this is. No coolant in the oil, and it just weeps a bit after the engine cools. While at running temp it expands enough to seal it up.
    Will this crack keep expanding? Does it weaken the deck surface? Stop leak and run it? Replace block? DSCN1008.JPG DSCN1011.JPG
  2. Forgot to add, the engine is a small block Chevy if it matters.
  3. Deuces
    Joined: Nov 3, 2009
    Posts: 18,471

    from Michigan

    It could be repaired.... You might have to pull the motor out and disassemble it....
    OLSKOOL57 likes this.
  4. Deuces
    Joined: Nov 3, 2009
    Posts: 18,471

    from Michigan

    If it's a 350, your better off replacing the block...
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  5. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,724


    I would peen it with a ballpeen hammer from both top and bottom. Them run some block sealer in the antifreeze. You can also coat the outside with some good epoxy.
  6. jaw22w
    Joined: Mar 2, 2013
    Posts: 976

    from Indiana

    I have welded cast iron successfully in the past. Preheat and nickel rod. I have also failed miserably. Welding cast iron can be a tricky thing. That being said, I would never even attempt that repair. It might could be done, but WHY? There are at least a couple million sbc blocks out there with no cracks. If that were mine I would clean off that area real well, slap some JB Weld on it and drive the shit out of it while I was looking for or building a replacement.
    rc57, texasred, 56shoebox and 7 others like this.
    Joined: Jan 7, 2016
    Posts: 1,662


    If you were a machine shop owner from Sulphur Springs TX and you had a cracked block in your shop truck you would have invented and used this:

    How It All Began: A Mom and Pop Operation
    The J-B Weld Company was founded in 1969 by Sam and Mary Bonham. Sam had discovered a need for a “cold weld” product to use in his truck service garage, instead of traditional torch welding. Working with a Texas A&M chemist, he formulated an original “tougher than steel” two-part epoxy and named it J-B Weld. Sam and Mary soon went from selling the product out of their car to auto parts jobbers across Texas, to selling it in stores throughout the U.S. and internationally.

    When I was a kid in the early 70's, I helped my grandfather pull an old Farmall tractor he used in the 40s and 50s from the old tractor shed, it had a crack in the block. He drilled a hole on either end of the crack, ground a V in the crack and cleaned it really well. He laid a bead of JB weld in the groove and then "textured" it with a rag or something, and unless you knew where the crack was, you would never have seen it. It didn't leak.
    Last edited: May 12, 2019
  8. rusty rocket
    Joined: Oct 30, 2011
    Posts: 3,796

    rusty rocket

    I had that happen a few years ago on a 327. Mine cracked so bad it pushed the casting out. I looked into fixes because I also did not have water in the oil. I found a welding rod called muggy weld. Ended up dropping a 350 crate motor in and the 327 sits in the corner waiting to be fixed some day.
  9. Deuces
    Joined: Nov 3, 2009
    Posts: 18,471

    from Michigan

    There's also the ol' school way of repairing the block... The old pipe plug trick....
    Maybe someone else here can explain it better than me....:oops:
    OLSKOOL57, Boneyard51 and Johnny Gee like this.
  10. mohead1
    Joined: Jan 18, 2013
    Posts: 557


    Devcon-Metal epoxy or JB Weld....gotta v-groove it, drill tiny holes on each end, clean and prep area very well. Clean and dry is important. Fill with product, use small tool to trowel or smooth, forcing it into the crack/holes. Should be good for awhile. This can also be TIG braised with bronze rod...but block may have to come out if not accessable easily

    Sent from my SM-G900V using Tapatalk
  11. anthony myrick
    Joined: Sep 4, 2009
    Posts: 5,539

    anthony myrick

    Here is an interesting way
    Google repairing a freeze crack in a block and several ways come up
    Welding, brazing, pinning, resins, additives to coolants
    Montana1 and Deuces like this.
  12. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 828


    I get a newer 350 with a roller cam set up and make the swap worth while..
    OLSKOOL57, Montana1 and Deuces like this.
  13. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,056

    from Berry, AL

    It can probably be fixed, but is it cost effective is the answer. A rare or hard to get block would get more attention on trying to fix it, where a more common SBC would be replaced. I had a 350 do that once, I junked it and bought another block cheaper that trying to fix it.
    OLSKOOL57 and Deuces like this.
  14. oldtom69
    Joined: Dec 6, 2009
    Posts: 479

    from grandin nd

    common spot for SBC to freeze crack-too thin there to fix by drilling and tapping over-lapping plugs.welding sometimes works ,but tends to chase the crack along.I'd clean it as well as possible and JB weld it-your'e not out much if it doesn't work!As far as any real repair,I agree its cheeper to replace the block
    OLSKOOL57, Deuces and Boneyard51 like this.
  15. TRENDZ
    Joined: Oct 16, 2018
    Posts: 173


    Look at it this way... It’s broke. No matter what you try, you can’t make it worse. I would drain it, drill the ends of the crack, rough up the block, and epoxy/ jb weld it. If it doesn’t work, you’re no worse off than you are now. If it works, you’re a hero.
  16. I have a friend who years ago had a casting defect on the side of his Detroit diesel, it was in the water jacket. He took it back to the dealer and they drilled the the spot out threaded the hole and JB welded in a 1 1/2" pipe plug. Held for a million miles.

    Sent from my SM-T837V using The H.A.M.B. mobile app
  17. LM14
    Joined: Dec 18, 2009
    Posts: 1,922

    from Iowa

    It's a common as dirt SBC block, why waste the time and money trying to fix it so it can let you down in the middle of nowhere. Those blocks are too easy to find to spend the time and effort to save it. take it as a sign it's time to refresh the engine and go on with life.
    alanp561, OLSKOOL57 and Deuces like this.
  18. irishsteve
    Joined: Jan 10, 2017
    Posts: 698


    Drill a hole on each end of the crack,and MIG braze it.
    OLSKOOL57, Deuces and Beanscoot like this.
  19. Thanks, I'm pretty sure I can seal up the leak. Was more concerned if the crack will keep "running" or if any other issues would happen from having a crack there.
    I hate to tear this engine down as it runs great with no other issues. Probably less than 30k miles on it.
    OLSKOOL57 and Deuces like this.
  20. oldolds
    Joined: Oct 18, 2010
    Posts: 2,949


    Can you get to it ti drill each end? Then drill and tap each end and do like the video above. You could even do the drill and tap stitch method. That is a good repair. If you have to pull it to do that I might just change the motor. If it has some expensive machine work I might pull it and stitch it, but if it is a stock motor I would probably replace it.
    The glass type block sealers seam to work ok. That should get you the season out of it before you change it. Lots of options. Do you feel lucky?
    OLSKOOL57 and Deuces like this.
  21. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,174


    Common area for a freeze crack to occur; also in the valley area, so you might want to check that out also (milkshake oil?). If it's just the outer, then "stitching" it works good, if done by someone with experience (try a diesel repair facility-those engines can cost $$$$$). If it's in the valley also, find another block. I am Butch/56sedandelivery.
    Last edited: May 12, 2019
    OLSKOOL57 and Deuces like this.
  22. Don't dick around with any of these half assed solutions. Stitch it up
  23. Jack E/NJ
    Joined: Mar 5, 2011
    Posts: 578

    Jack E/NJ
    from NJ

    >>>No coolant in the oil, and it just weeps a bit after the engine cools. While at running temp it expands enough to seal it up.>>>

    I dunno? Before concluding it's a real 'crack', you might want to try wiping the whole wet-looking area above and below the deck with a dry cloth when its weeping.. Then hold a dry cloth just above the crack and watch if the crack still weeps. The crack might only be a surface imperfection that effectively wicks coolant coming from above. Even if the temp got well below -20*F, I think the coolant would only turn to slush and not freeze solid enough to crack blocks or burst pipes. Jack E/NJ

    Deuces likes this.
  24. cheaper to replace the block its just a SBC
    Deuces likes this.
  25. Deuces
    Joined: Nov 3, 2009
    Posts: 18,471

    from Michigan

    We need to know if it's a 350... Roller maybe or a early '70s 2er4 bolt block.... What's the casting number in back of the block and the vin number??????......
  26. mohead1
    Joined: Jan 18, 2013
    Posts: 557


    The stitch method is a great thing for an expensive or hard to get block or other casting of some sort.....but way too much work for a small block....epoxy or weld and move on....ifnit starts leaking again, then you know the answer

    Sent from my SM-G900V using Tapatalk
    RMR&C likes this.
  27. mohead1
    Joined: Jan 18, 2013
    Posts: 557


    If not sure if n its cracked, pressure check the system and see where its leaking....cud very well be coming from the head gasket....

    Sent from my SM-G900V using Tapatalk
  28. Pete1
    Joined: Aug 23, 2004
    Posts: 1,725

    from Wa.

    Since it seems to be seeping very little, you have several options.
    1- Run it for awhile and see if it seals itself up with some silver seal in the cooling system.
    2- Stitch it. About a 2 to 3 hour job. Can be done without tearing the engine down. Rather expensive whether you do
    it yourself or have it done.
    3- Have it welded by a qualified shop. Finding one of those is not too easy. Here is a pic of a weld on a flathead Ford block where the frozen piece fell clear out. This was a one hour weld job with the engine still assembled.

    Weld patch 2 copy.png
    OLSKOOL57, Deuces and F&J like this.
  29. It's definitely a crack. The block is a 4 bolt main 350 from a '75 truck IIRC......nothing real special. Bored .030 with flat tops.
    I'm not gonna try to weld or stitch it. Probably just add some stop leak and keep an eye on it over the summer. Look for another block in the meantime as suggested above...
  30. Slopok
    Joined: Jan 30, 2012
    Posts: 2,519


    You need to replace with a Corvette engine this time!;)
    mgtstumpy, Montana1 and Deuces like this.

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