Smooth Engine Part Surfaces

After visiting the Coolspring power museum in Pennsylvania a few years back I noticed that most of the engines there looked like they were rust pit free. I was wondering what they do to them to make the parts look so good and smooth, do they resurface the parts or put some kind of filler on them, or just a really good thick primer? – Tanner

Most likely they grind the castings smooth using a floppy type grinding disk and then apply body putty over that. Then they use fill coat primers and next several coats of paint. As always the important work is well ahead of the pretty paint. – Doug

I'd advise not to put too much effort into smoothing cast iron engine parts. Some engines do get pitted more than others due to the elements, but original cast iron is supposed to have a somewhat rough look and feel to it. Its slight imperfections are what make cast iron from the olden days stand out as original. Even casting outfits these days remake parts a little too perfect.
I've seen many engines that have been grinded, sanded, and smoothed down way too much to where the cast iron looks like glass. This is about as far away from original condition for the engine as you can get. When these engines came off the factory line, the cast iron didn't look and feel like glass! In my opinion, engines that look like this have greatly decreased value. Collectors these days want engines in original condition. An engine that is over restored is not original and it will not have the same value on today’s market.
I've been to Coolspring and I'm not sure why some of their really old/rare engines in that concrete garage look so smooth. I do know they are mostly restored and came from a single collector, so maybe that person did a little over restoration. However, when you walk around to the rest of the buildings, you'll see many of the engines are in original unrestored condition and they have that slightly rough casting.
In my opinion, I'd highly advise against doing what Doug mentioned unless your engine has severe pitting that you want to get rid of. I believe there is nothing more damaging to a historical engine from the past than over-restoring it to something it never was. Put on too much primer, put on too much paint, but don't grind down that original roughness and putty the whole thing up. You can always recover an engine from too much paint, etc., but you can never bring back the original surface and feel once it has been sanded and grinded away. However, it's your engine! -- Jeff

I have an 8 HP Field Brundage engine I bought 35 years ago. At that time the thought was to sand blast down to bare metal and start over. I would not do that today to that engine as it had a lot of original paint but it did have a hole in the hopper tapped for 1 1/4 pipe for more water capacity to another tank. The finish was smooth and when sand blasting you could see a thick layer of a type of filler that they used to fill in casting imperfections. This was a quality engine and many cheap engines did not go through the trouble. I think most engine builders made some effort to turn out a nice looking product. I took the effort when I restored this engine and filled in and sanded and it looks smooth like it did originally. Don't be too quick to judge. – John

There is nothing like an old engine all slicked up sparkling and bright. I just stand there in amazement as to all the hours of labor it took to get it that nice looking. That’s on top of what it has taken to mechanically restore it. My engines start out all slicked and shiny and I even use car wax on them but they don’t look like that for long because I like to run them. That’s another reason I like them slicked, they clean up easier. Well that’s my side of the coin. -- Ken

I have never been to the Coolspring museum, but I have seen some pretty big engines (100+ HP) and one thing that they pretty much have in common is that they were used "inside" to power cider presses, line shafts, pumps etc. and they were permanently mounted. With this being said, it is easy to understand no pitting with having 75 to 100 years of sheltered life as compared to a FM Z that spent the last 40 years out in the fence row. So other than casting roughness, these sheltered engines would appear pretty smooth. – Keith

I have never seen an engine in original unrestored condition with castings so smooth that they looked like glass. However, I have never heard or considered that original manufactures took the time to putty up their engines to look smoother. I have seen many an engine with 90% original paint, stored inside all their life, with little wear to parts at all and they all have a slightly rough cast look and feel.
We have a 6HP Mogul that most likely never sat outside. It has smooth flywheel surfaces, the oiler and gas tank look like they were just riveted yesterday, yet the flywheel spokes, hopper, and base all have a slight rough feel. We lightly sanded and brushed off the old red paint (even saw slight remains of the original pea green paint) applied a light solution to clean off the dust, and then put on primer and a few coats of paint. The engine looks great, yet it doesn't feel as smooth as glass.
I think there might be a mix up about what degree of smoothness we are talking about here. Original castings are all pretty much smooth, but they also have a slight roughness to the touch. I'm just saying I don't think the surfaces should be as smooth as glass. I also just can't imagine that many companies put on a layer of putty over their castings before painting. Of the 100's of engines I've seen, touched, and restored, I've only seen a few that were restored and looked and felt as smooth as glass and in my head, I thought the engines couldn’t have originally been like that. -- Jeff

Hi, just had to jump in here, because I also prefer the original cast look. Remember the "help with Simplicity" thread Saturday March 1? Take another look at the picture. The black areas have a thick putty like filler over a very rough casting.
In the grease protected areas, the paint is almost automotive smooth over this filler. On the base flange where I cleaned away some of the grease, you can see the original dark olive paint.
I'm using a side grinder some places and a sanding disc others while trying to retain the best cast appearance. This experience tells me that maybe the engine builders did use filler to cover rough castings. -- Ralph

I agree with both, Most engines are best restored back to original condition. For example the little Ironwood I just finished (Picture in the Gallery). I wanted it to look like it did when the boy finished it at Ironwood High School. I did remove the forging "frost" that was under the original paint prior to repainting and removed most of the pattern tabs however. Even the hopper opening is rough and irregular and it will stay that way. In this case, it is part of the history of the engine. They were not professionals and the engine reflects that. Some of the expensive, large engines including many sideshafts had a fancy factory finish and should be restored accordingly in my opinion. -- Dean

Most engines I have collected need some sanding and filling. Some manufactures did not take any pains removing flashing or pimples. When I restore an engine, I finish what was probably a production process of cleaning flashing and grinding high spots. I do use body filler to slick the finish up. My reasoning is that it makes the engine easier to clean and hi-lights the lines the engine mfg. designed into it. If you look at some of the old ads, the engines appear clean and stream-lined. In reality they did not take the pains they did in the picture. Looks sell, and I like to see a smooth stream-lined look to an engine. If people took the pains to do that, then normally they were as meticulous about the mechanical restoration part. I don't collect engines to re-sell, so If I buy it, it's because I'm going to keep it. I do slick mine up a bit, but not like a new car finish. I’m going to keep doing it too, but to each his own: our main objective is to preserve these engines. – Pat

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