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#75826 Sun Apr 01 2007 09:55 PM
Joined: May 2006
Posts: 491
I've posted a few questions about how to deal with a cracked block, and after successfully fixing the crack with JB-weld last week I thought I would post this so that you can all sleep again. For those of you who are even greener than I am I have even a few recommendations of my own, so that you can avoid some small difficulties I was not so prepared for.
Last Thursday I got a package in the mail, special delivery from an anonymous source in Minnesota, a package of JB weld. It seems that in this day and age sending JB weld internationally is a threat to national security, don't tell my dad. Anyway I was able to persuade this anonymous source to send the JB-weld please, and since I had been waiting so long when it finally came the repair went pretty quick. I used a lot of tricks I read on this site, drilled out the ends of the crack, hooked up a shop-vac to the radiator, heated the area, ground and vee-d the crack, cleaned with brake-clean, and applied the JB weld. So here are some things I would mention to you really inexperienced guys like me, the rest of you can just ignore this part.
1) JB weld is pretty runny as applied. Since the block was in place, I had to apply the stuff on the side, and even if it feels solid as mixed, it takes a good long time to harden and it will have time to ooze downwards. Someone recommended turning the block on its side, this is surely a good idea when possible. But when not possible, be prepared that it will run.
2) The shop vac was a good idea but it did pull the glue through the drilled holes. So I shut it off soon after I started applying the glue.
3)Drilling the ends of the crack is surely a good idea. Finding the ends of the crack on an older engine is not so easy. I did not find the ends of the crack on my first try. In hindsight I would recommend - before draining the coolant, cleaning off the block, grinding the suspected area and drying it (if possible) and then starting the engine again to try to really find the end of the crack.
4) Some folks recommended using 40 grit sandpaper to texture the patch once the JBweld has set up. I let it sit a couple of hours before trying this, and the goo was still too loose, the sandpaper tended to want to pull the glue off the block or at least thin it out. You might let the stuff sit at least 4 hours before texturing the patch. Someone else said not to touch the glue at all after applying it. Personally I now subscribe to this advice - I am more concerned about a good repair than a texture
Finally I can say that my repair seemed to work, at least I have been driving the truck for 2 days now, probably 30 miles so far at around 50 mph, and the repair is nice and dry. I also have found a spare 216 in Stockholm (not so far from me) which I would like to snatch up as a reserve - I like to be realistic about the quality of my work. But until I find the time to pull the motor, I hope this JB weld will keep me on the road.

It may not be the easy way, but it is the Cowboy Way - Ranger Doug
Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri
1953 Chevy 3100
1960 Volvo PV 544
1941 Chevrolet Special Deluxe
#75827 Sun Apr 01 2007 11:43 PM
Joined: Dec 2006
Posts: 1,466
Shop Shark
Good job! I've heard that some folks have such good success with the JBweld that the patch outlasts the internal parts.

#75828 Mon Apr 02 2007 01:26 AM
Joined: Sep 2001
Posts: 31,812
Bubba - Curmudgeon

Excellent instructions.

I have had a non-leaking JB Weld repair on my 1960 261 block for over eight years. I followed almost all your steps, except the shop vac to the radiator.


Tim []
1954 3106 Carryall Suburban [] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [] - part of the family for 15 years
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engines are not "splash oilers" - this is a splash oiler. []
#75829 Mon Apr 02 2007 03:34 AM
Joined: Mar 2006
Posts: 77
Wrench Fetcher
Cool! My 235's block is cracked and someone gave me some JB-Weld to fix it with. I haven't had the chance to do it yet, but I'll sure follow these. Although, I must ask, how do you drill out the ends of the crack? I would be afraid I would mess it up even worse if I did it myself, Ha Ha!

Anyway, cool instructions!!! I'll certainly put them to use.

#75830 Mon Apr 02 2007 04:52 AM
Joined: Feb 2006
Posts: 112
i had a 73 blazer with about a 10 inch crack down the side of 1 head. i v'd the crack with a grinder, jb welded it. never leaked a drop in 10 years. i had a set of heads i was gonna put on it someday, but sold it before i got around to it. grin

#75831 Mon Apr 02 2007 07:45 PM
Joined: May 2006
Posts: 491
Robbie, I was a little worried when I started drilling those holes, but what the heck, if the block is already cracked then I don't need to worry about messing it up. If it succeeds, great - if it bombs I haven't really lost anything but a cracked block. If you saw the earlier threads you may have read that I broke off a drill bit inside the water jacket. That broken bit is still there I expect, mired in the muck. But I don't care, the engine runs great!

It may not be the easy way, but it is the Cowboy Way - Ranger Doug
Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri
1953 Chevy 3100
1960 Volvo PV 544
1941 Chevrolet Special Deluxe

Moderated by  Phak1, Woogeroo 

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