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Old 06-25-2003, 09:10 AM
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Post engine block welding

Has anyone had experience at welding a cast iron engine block?
I recently picked up a '64 corvette 327 block from a boat and upon disassembly found a crack in the lifter valley,just below the cylinder deck.
Anyone have any ideas or knowledge in this field?I've been doing some research on different web sites and there's lots of info but lots of conflicting idea's and methods
Any help would be appriecated,thanks

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Old 06-25-2003, 02:08 PM
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this is for flathead fords that were bad for cracking blocks, but I'm sure the tips will help you...joe

http://www.reds-headers.com/html/stacked_page_20.htm
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Old 06-25-2003, 07:39 PM
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Having welded many valuable cylinder heads over the years I feel I can offer some good advice.

First off there has been a revolution in welding electrode alloys in the last 10 years and there are many machinable alloys that approach the original casting in composition and strength without any of the old cast alloys hardness and cracking problems. You can thank powder metallurgy for the advance.

With that in mind I still use an old process that I learned from a nearly blind welder (No kidding he welded by feel).

First you need to construct an above ground pit or you can dig one big enough to contain your workpiece, as an alternative you can bake the engine block in a large industrial oven if you have access to one, 500 degrees F or higher is desirable. Ideally you want to cool the part as slowly as possible once your done welding.

Prepare the crack with a Vee shaped gouge at least 2/3's the depth of the crack, the Vee should have an included angle of 45 degrees or more. You can grind the Vee or use plasma or air arc to form the Vee. A U-shaped groove is acceptable also but the flux cap is harder to remove in-between passes.

Once the crack is prepared put the block in your oven or your pit and make sure you place the crack up so you can access it. If your using the pit method you will need enough charcoal briqettes to cover the bottom of the pit/enclosure plus cover the block completely by a few inches. Light her up and let her burn until half of the coal has been consumed, your block is ready for welding when it is a dark cherry red..in daylight it will appear grey.

Uncover the portion of the block where you will be welding and wire brush it thoroughly to clean, since the briquettes will be mostly ash by then, a shot of air can assist getting the ash out of the crack. Start welding using the GMAW process and technique (arc welding) and a rod of the correct size for your current setting, be aware you won't need as much current compared to doing this cold. Peen your weld vigorously in between passes with the pick end of a chipping hammer and wire brush the weld groove clean of all flux in-between passes.

When your welds are done, cover up the block with the excess ash and charcoal and leave it for a couple of days or until it is cool enough to touch. Finish the weld if you desire or leave it as is if the weld profile is not critical. If you are using an oven at 500 degrees F let it cook for at least 8 hours and leave it in the oven to cool...the slower the better.

Thats it, I promise this technique will never crack again since this is how I restore valve seats in old valuable cylinder heads and have never had a single failure yet. Typically the weld is as machinable as the original material and finishes nice enough that it will almost impossible to find the weld line. There will be no brittle zone since you have effectively heat treated the part at the same time you welded it.

Another technique that works well for non-critical areas is to use a stainless weld rod and peening in between passes, it doesn't look original but the nickel in the stainless acts as a glue and buffer in the HAZ (Heat Affected Zone) and will act as a cushion to prevent the crack from getting bigger and also flex at the same time. It works very well for exhaust manifolds and other thin sections. This technique usually needs no preheat but it doesn't hurt.

There are a few...ahem...stock appearing cylinder heads floating around Manitoba that are anything but, after a sandblast followed by a shotpeening I challenge anyone to tell if they had been modified by welding.

...and you thought the stock classes eliminated the big dollar racers.
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Old 06-26-2003, 09:10 AM
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Thanks for the info guys.
I knew about the oven technique,and I have an oven in my shop large enough to heat the block in,I was just hoping there was a newer,easier way to weld cast without all the time involved.
Any thoughts on silversoldering a crack?
I've found a web site which claims it will work on exhaust manifolds,but doesn't mention engine blocks.
thanks again for your input
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Old 06-26-2003, 09:54 AM
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Try the stainless technique it works great and is stonger than Silver. I would still bake it to burn off the oil in the casting though.
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Old 06-26-2003, 01:56 PM
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4 Jaw...

Hey THX for the "How-2" on welding cast iron. I actually stumbled on a similiar process about 3 years ago. I was welding up a exhuast manifold and used my BBQ to pre-heat & post-heat the part. I used a nickle "NI-CAD" rod about 3/16" dia. ...one differents between your method and mine is grinding your bevel area. I found that if your welding something less then 1/4" thick, no beveling is necessary because of the penetration with this rod. You have to weld with this with the "juice" turned way up!!!
BUT I have one question, I have a big block chevy head with cracks in the combution chamber. This is a semi-rare head number (409), would it be better/easier to try the stainless steel welding method or the NI-CAD rod?? ...Mark(11echo)
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Old 06-26-2003, 02:15 PM
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You might like this thread.
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Old 06-27-2003, 03:33 PM
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I once purchased a well run in 302 Chevy to put into my 70 Nova after I destroyed the original engine. We took it all apart to put a set of rings and bearings in it. When we took off one head I found the engine had been run a long time with a blown head gasket. A small "V" shaped groove was in the block right between two cylinders. We took the block to a well known local welder and he gas welded the groove up with a nickle rod. Faced the buildup with a flat file and sent me on my way. We reassembled the engine with original GM steel head gaskets, but we used small diameter solid copper wire in the groove of the head gasket around the cylinders. I drove that car back and forth between Abilene, Texas, and Nederland, Texas every two weeks for a solid year with zero problems. Eventually pulled the engine and replaced it with a fresh 350.

Vince
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