Cast Iron Repair on a 1914 SC-4

[rustyjazz1938]

Hello All,

 

As I've been going through the refresh on my 1914 SC-4, there has always been a bit of a major issue with the engine that has always given me fits since I bought the car:

 

 

As you can see, besides the impressive amount of crud that was built up on the engine over the years *yuck*, the exhaust manifold flange had crack sometime in the long history of the car. From the looks of it, the crack was very old, I did not have the missing piece, and it looks like it could have been due to a very thin spot in the casting itself, which can be seen in the side of the flange closer to the block. Probably this crack happened so long ago, it might have been the reason why the car was parked for an extended period of time. 

 

The issue of course is that this is a massive exhaust leak, and it happens to be right near the fire wall, so unless I was driving on a very windy day, I always felt a little bit groovy from the unburned hydrocarbons! 🤣 However of more concern, this leak would allow the exhaust to suck in oxygen from the air, which would mix with the unburned gas (I will be working on tuning the carb a bit as well) and cause a massive backfire in the exhaust on a throttle closing down transient. It was only a matter of time before the original muffler on the car had enough and scattered itself to kingdom come.

 

After some research and discussions with other car experts, a friend of mine and I decided to undertake a TIG brazing procedure with silicon bronze filler rod, which would be low temp enough to not force a lot of stress into the 106 year old cast iron and allow for some flexibility at the brazing joints due to the nature of the filler material. The stage was set:

 

 

I started with a piece of Schedule 40 pipe (had it easily available) which was 1/4" wall thickness and 2" ID. Amazingly this seemed to match very well in dimension with the remaining material on the exhaust flange, again making me think that the crack occurred because the casting was just a bit too thin on one side. The next major step was to take it to an experienced welder/TIG operator, of which I am most certainly not!

 

I have a friend in the local SE Michigan area, whom is also an antique car junkie, whom I have always jokingly said could "weld a ham sandwich to a tin can." He was gracious enough to help me through this endeavor and I loaded the engine into the back of my truck, which made it much easier to work on, and made my way over to his shop.

 

 

Here you can see the patient being prepped for surgery. We waited until the absolute last minute to clean the iron so there was relatively low risk of any flash rusting occurring. During the procedure, my friend would be manning the TIG torch, while I assisted with an oxy-acetylene torch to first preheat the iron, and then once he finished a pass with the TIG torch, provide post heat, all with the goal of trying to even the heat within the cast iron and minimize the stress from the procedure.

 

 

I managed to snap a quick photo of the process underway, a bit of a hairy thing, as I was balancing the lit oxy-acetylene torch and keeping my head turned as I only had oxy-acetylene rated goggles for the procedure. We had a piece of the original exhaust pipe to use as a guide while brazing to help with the alignment of the new piece with the old flange.

 

The final outcome of the procedure:

 

 

While not the prettiest (the cast iron was still pretty dirty and spitting a bit while he was working the TIG torch) the brazes look to be very clean and functional and with good penetration and alignment, with most importantly, no apparent stress cracks in the parent material from the heat cycling. We kept post heat on the iron for a while before letting it cool to room temperature and checking to see the outcome of the work. A good sign was the exhaust pipe itself was able to be removed from the flange, as intended, which indicated proper heat control, without welding the pipe in place.

 

All in all, I believe the work turned out very good, not too bad for two guys (engineers, always dangerous letting us work with our hands 😁) with limited experience in this field. I'll be keeping an eagle eye on the work as I get the car recommissioned and running again, but for right now, I am claiming a victory, as it should be a marked improvement over the original situation, and should allow me to not be gassed every time I take the car out!

 

Thanks for reading,

 

Rusty Berg

[Stude Light]

Nice repair job!. And another fine example of Cause and Effect. If the car wanders a lot, it may just be a cracked exhaust manifold. 🤪

Scott

[rustyjazz1938]

Hi Scott,

 

I guess I can't use that excuse anymore with the local law enforcement officers when I get zinged. 😃 I have a backup with the king pins just in case... 🤪

 

Thanks for reading,

 

Rusty Berg

[Bloo]

How does the pipe attach? Is there packing in there or something?

 

 

[rustyjazz1938]

Hi @BobinVirginia

 

I don't think I want to risk the needle scaler given how thing the casting is on the one side, that being said the bleach flash rust process might be a nice touch to hide the fix, especially given the rest of the engine condition. It also helps that this butts up against the fire wall of the car, so its visibility will be limited.

 

Hi @Bloo

 

As best as I can tell the pipe is a slip fit into the sleeve. It's a very tight slip fit, and I am assuming it carbons up a bit as a means of providing extra sealing capability like some Diesel engine slip fit exhaust manifolds. There is an exhaust hanger on the main pipe pretty close that I think helps to limit the relative motion of the pipe within the flange, but as evidenced by the original crack it's probably not the best setup.

 

Thanks for reading,

 

Rusty Berg