Re: Ken's 1937 115C Touring Sedan
Posted by Ken_P On 2014/12/31 20:40:40
I fixed the crack in the block today, using stitch pins from Lock-N-Stitch. It went very well- I laid out all of my tools ahead of time and was able to fix a 4.5" crack in 2.5 hours, including time for shop clean up. I used 31 pins.
A few lessons learned- doing the production line technique is the way to go. I didn't feel like springing $130 for the precision drill guide, so I made a series of overlapping holes by outlining holes using a drill sizer (7/32" diameter for the pins I was using) and then center punched and drilled every third hole. Then I spot faced \the holes, tapped them, installed the pins, and ground them flat. I initially used a grinding wheel in my angle grinder, but this was too easy to chew up the block with, so I switched to a flap wheel. After the first series was done, I went back and did the whole process 2 more times. It is key to only drill into one side of an installed pin, hence the three part series instead of two.
The instructions also said to leave a little material from each pin above the parent metal until the very end to be able to locate each pin, but I blended immediately so the drill stop on my spot facer did not need to be continually re-adjusted. I found the pins and cast iron to be different enough that I could still see each pin.
I used a cordless drill for the spot facer. Its max RPM in low range is 300 RPM, which was just right for the spot facer. Finished off with the needle scaler, and it's done! The repaired spot is slightly concave- I'm not sure if I hammered the crack back together too hard prior to repairing, or if the needle scaler pushed it in slightly. I threw a quick thin layer of paint on, just to see how it would look.
I do have some more needle scaling to do, as the repaired area is still smoother than the rest of the casting, but it is repaired. Once I get the new valve guides installed and the cylinders honed, it is off to the machine shop.
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A few lessons learned- doing the production line technique is the way to go. I didn't feel like springing $130 for the precision drill guide, so I made a series of overlapping holes by outlining holes using a drill sizer (7/32" diameter for the pins I was using) and then center punched and drilled every third hole. Then I spot faced \the holes, tapped them, installed the pins, and ground them flat. I initially used a grinding wheel in my angle grinder, but this was too easy to chew up the block with, so I switched to a flap wheel. After the first series was done, I went back and did the whole process 2 more times. It is key to only drill into one side of an installed pin, hence the three part series instead of two.
The instructions also said to leave a little material from each pin above the parent metal until the very end to be able to locate each pin, but I blended immediately so the drill stop on my spot facer did not need to be continually re-adjusted. I found the pins and cast iron to be different enough that I could still see each pin.
I used a cordless drill for the spot facer. Its max RPM in low range is 300 RPM, which was just right for the spot facer. Finished off with the needle scaler, and it's done! The repaired spot is slightly concave- I'm not sure if I hammered the crack back together too hard prior to repairing, or if the needle scaler pushed it in slightly. I threw a quick thin layer of paint on, just to see how it would look.
I do have some more needle scaling to do, as the repaired area is still smoother than the rest of the casting, but it is repaired. Once I get the new valve guides installed and the cylinders honed, it is off to the machine shop.
Attach file:
(68.00 KB)
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(62.04 KB)
(70.64 KB)
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