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Post Info TOPIC: Fixing cast iron


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Fixing cast iron


I have a set of Pontiac heads that are desirable but one has a crack. The only method that i have heard that seems to be viable is called stitching. The process involves using plugs that are screwed into the crack. The plugs overlap each other and i was told this works very well. I am looking for opinions from anyone that has done this. The heads are from  a 70 GTO and it is a waste to let them sit on a shelf.The crack is just below the valve cover rail which is a water jacket area. I would appreciate any feedback.  

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AAK

Dorchester Ont



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OK, I don't know about car parts.....

But at work when they fix Cast, they grind out both sides if the crack so you have a V, then they use a stick welder to fill in the V, or weld it back together, then grind it down. I am pretty sure they use a special rod as well, could probably find out if you want. Now I don't know if the heat would affect the heads or not?????

Just what I've seen.....hope it helps!!!!! shrug.gif

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John

1972 Pontiac Lemans (daughter's car) 
2005 Pontiac Grand Am
2004 Ford Explorer Sport Trac



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The heat will not affect the heads but with cast iron you have to put them in a oven to warm them first. I used to weld pump housings when i was a millwright and that is the procedure i used.
The crack obviously is only accesible from the one side and more than a few hotrodders have had issues welding them . The water jacket pressure is only 14-16 pounds but to get the proper weld penetration is tricky.

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AAK

Dorchester Ont



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Good to know.... I will chat up a guy at work, see if he has heard or done anything with the plug idea. If I hear of anything that would help, I will pass it along!!!

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John

1972 Pontiac Lemans (daughter's car) 
2005 Pontiac Grand Am
2004 Ford Explorer Sport Trac



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Thanks John i have never had to deal with this problem before(lucky) and i know these are too good to toss away.

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AAK

Dorchester Ont



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check into DEVCON liquid steel , and other industrial epoxies. I used Devcon to repair a water jacket crack just above the pan rail on a SBC years ago, file the steel in ONE direction to give it tooth.

there are some amazing chemicals out there, being this isn't in the compression area, it's worth looking into.


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later...rog

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I'm a collector...not a builder!!Located in sunny central Saskatchewan at the lakehead!


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I will give it a look thanks.

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AAK

Dorchester Ont



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Anytime I've seen cast repairs the above method was done, but they also drilled a small hole at each end of the crack to stop it"travelling" when the welding starts. My 2cents worth!!!

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Yes i have used that same technique when i have done repairs it is a good idea to drill half way into the material weather its steel/cast/aluminum.

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AAK

Dorchester Ont



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unburt wrote:

I have a set of Pontiac heads that are desirable but one has a crack. The only method that i have heard that seems to be viable is called stitching. The process involves using plugs that are screwed into the crack. The plugs overlap each other and i was told this works very well. I am looking for opinions from anyone that has done this. The heads are from  a 70 GTO and it is a waste to let them sit on a shelf.The crack is just below the valve cover rail which is a water jacket area. I would appreciate any feedback.  



I have had a number of blocks and heads stitched with the plugs. Works 100%. Have to think about all the blocks that got scraped years back when now there is an easy fix.

 



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Thanks Kevin for the good news ,i dont know anyone that has had this done this but i will talk to a machine shop in the upcoming week to get there price.
I would do this myself but i understand that the the drill and tapp set are expensive because of the tapered design.

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AAK

Dorchester Ont



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I would let the pros do it.

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Sorry it took so long to get back....the guy was sick the rest of the week. He said the stitching with plugs works well. He fixed a 4" crack in a Massey block. If you are attempting it yourself he said time is the big thing....take your time doing it......but I agree I would let the pro's do it!!!!!!!!!

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John

1972 Pontiac Lemans (daughter's car) 
2005 Pontiac Grand Am
2004 Ford Explorer Sport Trac



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Thanks John for the reply, i will talk to a machine shop in town and see there price. I was told that it is approx $ 125 an inch. I used to be a millwright and am not afraid to do this type of work and i have a decent drill press at home.
I am also searching out a supplier for this type of tap/ drill set.


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AAK

Dorchester Ont



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i have a 396 that the block was broken were the starter bolts to the blocks outer bolt hole, i welded it up with an arc welder using a nickel rod 10 years ago and has been fine. it has 11 to 1 compression and has held the starter on with out problem!

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The cast iron stitches come in a kit usually with the drill and tap.

It has to be a "closed crack" to be able to be stitched. That is, both ends of the crack have to be enclosed, and can be drilled to stop the crack from spreading (cracks won't spread through a radius). Any other type of crack needs to be welded or brazed.

Brazing is fine 99% of the time and doesn't have nearly the same chance of re-cracking next to the weld.

If its an external crack from freezing - drill both ends of the crack to stop it from propagating, grind it out in a v, degrease it to make sure its prefectly clean - then just epoxy it with something like JB Weld or Devcon. Once you sand it down and paint it, you will barely be able to tell its there.


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I did a SBC yrs ago right by the oil fiter boss. Oil was pouring out here when we fired it. Machine shop missed the crack on rebuild. cleaned out the crack & used the J/B weld on it, sealed it right up. Engine is still going in a 56 Chevy!!!!

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have had good results using NYROD welding rods for welding cast definately warm up the part to be welded with a torch,short welds and tap them in with hammer,for a smooth finish you can add braze,ive seen cast cracks 8 inches long brazed and hold.That rod kicks ass and if you can stick weld at all you can do it for the price of the rods,and buy beer with the money saved.i like beer

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unburt wrote:

I have a set of Pontiac heads that are desirable but one has a crack. The only method that i have heard that seems to be viable is called stitching. The process involves using plugs that are screwed into the crack. The plugs overlap each other and i was told this works very well. I am looking for opinions from anyone that has done this. The heads are from  a 70 GTO and it is a waste to let them sit on a shelf.The crack is just below the valve cover rail which is a water jacket area. I would appreciate any feedback.  

 What is the casting on your 70 Heads and where is the crack?

 

Pete



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Pete
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