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Can it be fixed and is it worth fixing. Best guess is fluid in head bolt hole caused crack. Noticed this after engine was freshened up. This is a sleeved ls7 block. Small crack here leaking coolant.
Like a cast iron block drill both ends of the crack. Wallow out a groove between the two holes with a die grinder. Then depending the thickness of the area of the block tig it closed. The bad thing is it may be cracked on the inside? Or farther than you see on the outside?
Like a cast iron block drill both ends of the crack. Wallow out a groove between the two holes with a die grinder. Then depending the thickness of the area of the block tig it closed. The bad thing is it may be cracked on the inside? Or farther than you see on the outside?
Good points on it being cracked thru to the inside. However, even if it is, I believe with a good welder, emphasis on VERY GOOD ALUMINUM WELDER. and maybe even some steel epoxy, intelligently applied, this block is salvageable. One point I'd like to make is this; due to GM discontinuing the LS7 block, I think you're going to see more and more damaged LS7 blocks being repaired, if they can be, rather than junked. If this was my block, Id disassemble it, do a high quality fix as best as can be done, reassemble it, and spend an hour or two on an engine dyno before throwing it between the frame rails. I'm not doubting the OP, but try as I might, with my old *** eyes, I cannot see the crack inside the blue oval (And I don't mean Ford!!).
Last edited by grinder11; Jun 27, 2022 at 05:51 PM.
Good points on it being cracked thru to the inside. However, even if it is, I believe with a good welder, emphasis on VERY GOOD ALUMINUM WELDER. and maybe even some steel epoxy, intelligently applied, this block is salvageable. One point I'd like to make is this; due to GM discontinuing the LS7 block, I think you're going to see more and more damaged LS7 blocks being repaired, if they can be, rather than junked. If this was my block, Id disassemble it, do a high quality fix as best as can be done, reassemble it, and spend an hour or two on an engine dyno before throwing it between the frame rails. I'm not doubting the OP, but try as I might, with my old *** eyes, I cannot see the crack inside the blue oval (And I don't mean Ford!!).
blue oval is basically underlining the crack. Focus on the coolant weeping out of the crack…dry block above crack. It looks to be 4-5 inches long from what I can see. Crack is whitish in color. It’s a big one. But I agree with you on repairing this block. I would try it. I’ve successfully repaired an iron bow tie splayed main block that froze and busted, and I was told it couldn’t be done with cast iron. I believe this can be repaired. With a set of headgaskets, torque plates, a modified water pump, and a couple other easily made items, this can be pressure tested before it ever goes back into re-assemble mode. The heat from welding the repair will likely make something move around, even down on the side, so it may need decked and a hone…maybe not. Have to be diligent and thoroughly check everything before re-assembly is considered.
Youguessit, if you want to sell this, shoot me a pm.
blue oval is basically underlining the crack. Focus on the coolant weeping out of the crack…dry block above crack. It looks to be 4-5 inches long from what I can see. Crack is whitish in color. It’s a big one. But I agree with you on repairing this block. I would try it. I’ve successfully repaired an iron bow tie splayed main block that froze and busted, and I was told it couldn’t be done with cast iron. I believe this can be repaired. With a set of headgaskets, torque plates, a modified water pump, and a couple other easily made items, this can be pressure tested before it ever goes back into re-assemble mode. The heat from welding the repair will likely make something move around, even down on the side, so it may need decked and a hone…maybe not. Have to be diligent and thoroughly check everything before re-assembly is considered.
Youguessit, if you want to sell this, shoot me a pm.
OK, I see it now. Looking too hard at the blue oval. Thats what I get for looking at Ford symbols, lol!! Anyway, I believe that it's all in the welders hands. A really good, certified welder who welds aluminum could do something successfully with it. Probably wouldn't be cheap, but cheaper than a new block. Yes, I think you're idea pressure checking the block, is better than mine on the dyno. The only thing I'll say about the dyno is you'll get actual, dynamic results with the motor being tested under load, which could expose a problem in actual running conditions. But pressure testing would be first step. Good call......
Last edited by grinder11; Jun 28, 2022 at 11:20 AM.
blue oval is basically underlining the crack. Focus on the coolant weeping out of the crack…dry block above crack. It looks to be 4-5 inches long from what I can see. Crack is whitish in color. It’s a big one. But I agree with you on repairing this block. I would try it. I’ve successfully repaired an iron bow tie splayed main block that froze and busted, and I was told it couldn’t be done with cast iron. I believe this can be repaired. With a set of headgaskets, torque plates, a modified water pump, and a couple other easily made items, this can be pressure tested before it ever goes back into re-assemble mode. The heat from welding the repair will likely make something move around, even down on the side, so it may need decked and a hone…maybe not. Have to be diligent and thoroughly check everything before re-assembly is considered.
Youguessit, if you want to sell this, shoot me a pm.
The crack is indeed inside the blue circle...not above. What you are seeing around the wet part of the block is residue. It may spread outside the blue circle as well but I cant tell. The only way I could see it was to get the engine running and hot; to build up enough pressure to push coolant through. I could not see the crack itself but the coolant SLOWLY being forced out.
I will have to look around and see what shops have experience with block repairs. I've only ever heard of high end billet blocks being repaired. If I had to guess I'd say the stress from the weld and the difference in the expansion coefficients between the filler and cast aluminum become a problem. That along with the stress created by the weld could cause failure during heat cycles.
Is the crack by the motor mount and is that why it is cracked so not sure this will not create another crack again (I know you can fix aluminum but not all cracks are equal either). Take to an expert but it may be better piece-of-mind with just a new block.
The crack is indeed inside the blue circle...not above. What you are seeing around the wet part of the block is residue. It may spread outside the blue circle as well but I cant tell. The only way I could see it was to get the engine running and hot; to build up enough pressure to push coolant through. I could not see the crack itself but the coolant SLOWLY being forced out.
Gotcha. I don’t see anything inside the circle, but I believe you. The white line at the top of the coolant line looks like a crack to me. My apologies. Again, if you want to sell, send me a pm.
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Ls7 block crack 
