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Discussion Starter · #1 ·
I'm new to the site and it is great, so here is my first post I have a grouted 400 sbc that has a crack about 1/4 to 3/8 inch long in a cylinder wall by one of the steam holes.The steam holes have been plugged. I use to run regular coolant but when the coolant system would build pressure it would leak back into the cylinder and fill the bore with coolant from the psi so i switched to EVAN'S coolant and there is coolant still getting into the motor but not nearly as much. I was told there was some kind of sealant or something i could get from a pharmacy that might seal it up. Any advice would be helpful. It is a street car that does see the strip on occation with a best of 10.66 @ 128 on motor. Thanks Rusty
 

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I suggest you look into the new Dart block they have out and through that block away. The only good repair is to sleeve the block and this one is not worth it because it will just happen in another cyl. I have broken 2 in the past and wont do it agian. Good luck
 

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Discussion Starter · #3 ·
I would like to buy a new block but this one is bored 4.165 if i buy a new block i would have to buy new pistons also $$$. I want to use this one as long as i can before i go that route. Thanks Rusty
 

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I had a ford motor do that to me once, but it was in the opposite direction. The motor would heat up and the crack would expand and then combustion pressure would start to pressurize the cooling system. It was pretty neat to see the radiator hoses expanding to twice their normal size!
 

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I would like to buy a new block but this one is bored 4.165 if i buy a new block i would have to buy new pistons also $$$. I want to use this one as long as i can before i go that route. Thanks Rusty
You're askin for a lot of trouble with any attempted repair...
Save yourself from a lot of additional grief.. Make a doorstop out of it..
 

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about all the stock 400 blocks are good for is cracking a cylinder wall. save yourself a lot of money and get a good after market block. you will be glad you did.
 

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Like some of the other guys said - what you're talking about doing is just a temporary fix. It might work on a everyday low compression engine but with the hi perf stuff it just doesn't fair well. Last thing you want is to lose the whole engine, replacing the block is the best option especially with the 400 blocks. Too many other better options out there. Find somebody that's running a blown methanol engine - they can fill it and run it with no water and be reasonably safe.
 

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Turbo Buick guys like the GM Cooling System Seal Tabs, p/n 3634621. You can get them at your local stealership, or you might find the same product on a hook at the local auto parts store with Bars Leaks branding (same packaging, same product). I used it in my truck, and it seems it may have worked. Crush up the pills and dissolve them in hot water before you put them in.
 

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Been there done that do yourself a huge favor and junk the block. I replaced my filled stock block with a Dart Little M and never looked back. First one I cracked a cyl bore. Second one I broke 3 main caps on it. I wasn't going for 3 strikes lol. I will say this also your bearings and rings will look even better with an aftermarket block and you may even pick up some power. The dart blocks matereal and strength make them much more stable under the conditions we subject them to. The above posts are right if the remainder of that cyl wall decides to fail you will end up with a big pile of scrap. Its no issue with a little M to take it to 4.165" they can go to 4.185" with no issues and some guys go 4.200 on them (sonic check them first of course) On the other hand 4.155 is about all I would want to go on a stock 400 so your already in no mans land, just my 2 cents

Craig
 
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