I have a small block chevy motor that has a cracked block. The crack is on the outside between two freeze plugs. Crack is about an inch long. Is this something that can be fixed or is the block junk?
If it were mine, it would be scrap. But it kind of depends what small block it is, if it's something rare and valuable, then it could be worth saving.
Sounds like it can be stitched OK. But if it was my block and not used in a critical application, I'd probably first try JB Weld to see if it'd hold. Jack E/NJ
Jim>>>if it's something rare and valuable, then it could be worth saving. >>> Which do you consider the most rare & valuable? Jack E/NJ
A real 302. Early 283 or 327. Aluminum Donovan block. In other words, can you get another block easily that will match what you have?
>>>A real 302. Early 283 or 327. Aluminum Donovan block. In other words, can you get another block easily that will match what you have? >>> Gee, and here I always thought the original bone stock 265 in my '55 might be worth saving if'n it ever got a crack like that. 8^) Jack E/NJ <!-- / message --><!-- sig -->
It's a 400 flat top motor that I raced in my dirt mod 2 nights. It has all new parts and I would like to try something before I spent the money I could use somewhere else.
There is a technique used called stitch welding. It was done on my L216 by the re-builder. It is apparently the way to fix a crack. It appears they embed two pins, one at each end of the crack. They then drill a series of pin-holes on each side of the crack the full length. That's what it looked like to me anyway. Then they weld it somehow. What made me panic was, it held air pressure just fine, but when I added coolant, it wept droplets of coolant. I called the rebuilder and he sent me some sealant in the form of two pills that I simply had to drop down the radiator. (Another old-school-er had me use JBWeld to fill over the area and then sand it down and repaint it. Then add the pills.) There is no more weeping, and everything is dry as a bone. It was expensive to have done, as I was given the option to have it welded for $600 or send him a new core. Well they were competitive with each other price wise, so I went with the weld, as who's to say the new core didn't have a crack also? Well good luck! And you may want to ask someone who knows better about stitch welding if it interest you.
Welding can work, but it has to be done exactly properly, or it will fail. Otherwise there is this: http://www.locknstitch.com/
Drill a hole at the end of the crack, clean the area bare, "V" the crack out to the freeze out plug , do not grind into the freeze out plug wall. Fill the area with JB weld. Let dry and install a new freeze out plug coating with something like okd style permitex. The whole thing will not cost that much and if it fails then consider replacement. Let me know how it works.
Gimpyshotrods...great link! I was wondering how it was actually done. I can see why it was so expensive. Apparently very time consuming. Thanks!
Based on what you described the block COULD be fixed. Whether it should be fixed is another matter. What you apparently don't know is whether there is more damage. Unless a block is rare or expensive, or has a lot of expensive work done to it, I wouldn't invest the effort or expense to fix it.
The crack is surprisingly not at a freeze plug. It is between two freeze plugs. I dropped the pan and there was no moisture in it. The oil was also clean. I am going to try and fix it. If it doesn't work then I will replace the block.
I would be concerned that it may be cracked somewhere else that you can't see. I have welded outside cracks like that with Nickle rods made for cast iron welding, but only in non-critical places like yours.
Bought a 305 marine crate motor about 20 years ago. We had an early nov. freeze and the block cracked in the same area as yours. Upon investigation the thickness of the block in that area was only about .040! Mind you- this was a new block! Not thick enouph for most repair methods.
A big X2! Would you glue your freakin' car together!?!? There are some out there that think that JB Weld is the 2nd coming of Christ when it comes to fixing anything. These are usually the same folks that believe in "mechanic in a bottle". JB Weld is a glue, no more... no less! Weld it the correct way as others have mentioned (with Nickle rod) or get another block. Why fuck around!
there's also putting just plugs into the crack, start at one end, drill and tap a hole, fill it with allthread, drill a new hole half into the threaded rod half in the block thread in a piece of allthread, repeat until the crack is filled grind flat and seal, that's how they repair heads with cracks, there are tons of vehicles on the market with rebuilt parts store cylinder heads on the road with this type of repairs..
Well. let's see... All SBCs are corvette motors. Corvettes are fibreglass. Fibreglass can be glued, so...
I tried some rods called super missile rods. Use a tight with them,they weld cast iron GREAT! preheat threa a little first. Weld and let me cool slow. It will work fine.
One thing to keep in mind when welding or having a block welded, it may have other stress issues. Sometimes a small crack might be a sign of a casting flaw in that block. I was rebuilding a 427 for my car and the machine shop called me to say they found a small 3/8" long crack at the bottom of one bore, and did I want it welded? Of course I didn't want to spend money rebuilding a block, and have it open up later, so told them to go ahead. They sent it out to a shop that specializes in block welding and they drilled the end of the crack, put the block in an oven to heat it, then welded it right up. After welding they covered it with a blanket and put it back in the oven to let it cool slowly. A few minutes later they heard a loud "bang" from the oven and went to check it out. The block had split in half down the lifter galley side to side making two V4's. From what I have learned since then, I'd never have any block welded unless it was something I had to have to keep a car numbers matching.
First, the ones against JB weld are correct, it is a glue and won't fix the problem. Second, you are dealing with cast iron, using all thread to "stitch" it closed will work, but eventually will fail. Steel all thread will not expand and contract at the same rate as the block, and will eventually leak or open up the crack further. Finally, welding is a great answer, but most of the above posts left out that you need to drill a hole at the very end of the crack to keep it from continuing. With that said, an engine rebuilder that does any kind of block repair can most likely give you a source for cast iron all thread to stitch with. It is a time consuming process because you drill a hole, tap a hole then thread the piece in. It breaks off at a predetermined torque, then you drill another hole, cutting half into the block and half into the rod you just screwed in. Tap that hole, thread in the rod and continue untill the entire crack is filled. This does work well, and I have seen the repair last for decades. As said by others, there is no cheap way to fix a cracked block, so cost of repair vs. block replacement should be considered.
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