Cast Iron Engine Repair 1940 V16 Lock-n-Stitch and Welding

Started by JLB, October 21, 2021, 02:47:43 PM

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JLB

Sharing knowledge gained upon discovering significant engine block damage to a 1940 V16. After a few hours of study I will not take a position on how to do this right. I am posting knowledge gained from two websites:

(1) Lock-n-Stitch website http://www.locknstitch.com/

(2) Pictures from "Freewheeling Tony Smith" facebook page

From Lock-n-Stitch: (also see the powerpoint material)

We want to share some truths about cast iron welding with you. These truths are easy to understand, extremely important to know and yet, ironically, hardly known in the welding world.

About 40% of the casting repair work that we perform in our service department is performed by some type of welding procedure. Even though we are the world leader and only complete supplier of metal stitching supplies in the world, we are also the only company who will actually tell you the truth without bias. Some repairs require oven welding and some require metal stitching.

The most important thing for you to understand is that electric welding on cast iron is actually the very worst decision you could make to attempt to repair your cracked cast iron part. If you want to make a complete mess of your part, go ahead and arc weld it with nickel rod. Cast iron cannot stretch and withstand the contraction and hardening caused by cast welding with preheating below 1200 ° F. The brand of welding rod does not make a very big difference. It's the heat that causes the changes to the cast iron itself. Sure the nickel weld is machineable but the cast iron will become as hard as a drill bit or tap and therefore will prevent the proper machining that is often required. 50% of the casting repairs we see have been arc welded on with disastrous results often costing the owner at least twice as much to repair properly. Cast iron welding should not be attempted even by experienced welders without years of high temperature oven welding training. Cast iron requires preheat of at least 900 ° F. for brazing and 1300 ° F. for fusion welding.

The attached pictures are from Tony Smith:


Jim LeBlanc
jim_leblanc@yahoo.com
1940 V16 Town Car
CLC Member #33340

dn010

I was able to successfully weld severely cracked cast exhaust manifolds without preheating and without them turning into dust, the only suggestion I received if I wasn't going to preheat them was - "don't let them get hot" by doing a very small section at a time and allowing them to cool between welds, and it worked for me. It was more of an experiment that worked out well in the end and if the manifolds were ruined it was no loss. They are still (somehow) in service to this day but it was a very tedious and time consuming repair.

I have been welding for over 20 years and unless it was a block that was easy to replace and cheap (like the manifolds above), I don't think I'd attempt a weld on one. I had no idea about the lock-n-stitch method of repair until I came across your V16 threads. I am also not trying to take a position of what is right or wrong, but I did want to thank you for posting this because it is a very interesting method of repair that I didn't know about. I ended up watching a youtube from locknstitch this morning to see how it is done.
-----Dan Benedek
'57 Cadillac Sedan Deville 6239DX
'81 DMC DeLorean