How To Restore Engine Tin
Article and Pictures by Mark Trotta
On small engines, sheet metal pieces are often referred to as tin. These include the blower housing and starter housing, as well as any shrouds or deflector shields that the motor may have. Metal gas tank restoration will require the extra steps of cleaning and/or sealing the inside of the tank.
Through decades of sitting, the tin on this vintage Tecumseh engine developed patches of rust, and in a few spots had started to eat away the metal.
Restoring engine tin back to it's original condition can be accomplished in several ways. The method described in this article is grinding, filing, and sanding down to smooth bare metal, then priming and painting.
Rust Removal Alternatives
Metal work is not for everyone, and there are several options. Engine tin can also be media-blasted, but I don't have access to one, and it would have been an unnecessary step to farm out. I have also seen good results with electrolysis, but I believe that this method is better suited when you have five or more parts to refurbish.
The tools that I used to refurb the engine tin were an air-grinder, die-grinder, bench-grinder, and Dremel-type electric tool. You probably don't need all these tools to get the same results; however they are all great tools and serve many other uses.
After the blower housing was off the motor, I started by removing the majority of the old paint with a bench grinder. To remove the rest of the paint and the rust from the blower housing, the starter housing needed to be removed.
Starter Housing Removal
Early low to medium horsepower Tecumseh engines had a "teardrop" shaped starter housing. It is removed from the blower housing by drilling out the four pop rivets.
If you have a drill press, this is an easy chore. If not, a hand-held drill works just as well, it just takes longer.
To remove the old rivets, I used a 3/16" drill and they came out with no incident. To re-install, I will be using stainless 12-32 machine bolts with lock nuts.
Rust Removal Procedure
Starting with a hand-held piece of coarse Emory cloth, I "checked" or cross-hatched the housing left and right, and then up and down.
The check marks give you a visual of how much you've sanded off, so you don't sand down too far (or not far enough) in one area.
For the heavily-rusted areas, I brought out my 5" air grinder with a 40 grit disc. This quickly removes the heavy stuff, but caution must be used or you'll take too much off in one area. That's why the cross-hatch marks are helpful, to keep metal removal even.
After a couple sessions with the air grinder, I went over the metal again with the Emory cloth, making new checking patterns. I then switched to fine Emory cloth and die-grinder with a Scotch-Brite pad.
After cleaning, I painted the starter housing with gray self-etching primer.
Blower Housing Restoration
Depending on what kind of condition your engine tin is in, additional repair may be needed. There were a couple of distorted bolt holes on this blower housing, which were straightened out with a hammer and dolly.
To remove the rust on the shroud, I followed the same procedures as the starter housing; several sessions with Emory cloth and an air grinder and die grinder. Afterwards, I sprayed the housing with brake parts cleaner, then dried with an air hose.
I primed the housing and let sit overnight before spraying the color coat.
If you've done decent prep work, special paints or powder coats are not necessary.
No clear coat was used nor is necessary.
I have sprayed many different brands of paints, and I really don't prefer one over another. All the top name brands are good when used correctly.
I do prefer a particular brand of primer, which is SEM light grey.