A great deal of the traffic on the Stationary Engine Mailing List over the last two months has been on the subject of the Tri-State Gas Engine and Tractor Show at Portland, Indiana: preparation for the show and impressions afterwards. As it must be one of the largest engine shows in world, it seemed an ideal place for a meeting of those whose normal method of communication is via a computer keyboard, so we traveled, from England, Australia, Canada, and from coast to coast of the United States, by commercial jet, private plane, truck and car to meet, mostly for the first time.
No one went away disappointed, and much as I would love to pass on some of the comments made about the meeting (votes are not all in yet as most of the Australian contingent are still traveling homewards as I type), I must bear in mind that technical information is more sought after than show reports, and pass on instead some of the expertise which has come to light in other 'threads' of discussion.
The subject of the 'finish' on an engine is one which crops up regularly and frequently stimulates a lively exchange, to which the usual outcome is to leave it original, to shine it up to a perfection not even seen in the factory--or anything in between. It's an entirely individual preference, and the variety, as in the choice of engine, is one of the many things which adds interest at a show. However, at some stage, almost everyone needs to paint all or part of an engine, and the following advice surfaced from those around the world who have tried and tested many different methods.
I have found that body filler is best for deeper holes as it has more body and strength. Most spray putty will separate in layers if applied too thick and is best used in thin layer coats. One way is to use the body filler, then smooth it back with a sander with maybe 100/200 grit and the use of a light layer of body putty which can be smoothed a lot easier with finer paper.
You can get glazing compound at most automotive supply houses to use as a filler. Sand it, put on a good heavy coat of primer and then paint only after the primer has cured. The paint will flow and do a great job.
Glazing compound is fine for filling in paint shop size holes--but Icing will work much better in a rough casting. An added advantage is that it sands easily can be sanded about 15 minutes after it's applied!
Prime first, then fill. Use Icing (or a similar product), then paint using a good automotive paint with a hardener in it. It's okay to prime before filling but do NOT use an etching primer under the filler. This primer contains acid and your filler won't hold on it very well. Don't bother to sand after priming. You will be sanding after using the Icing and then priming again prior to applying the paint. Primer is not always necessary if you use the right kind of paint, but, on rough cast iron, your finish will look better when primed.
I routinely use the damp proof red primer over rusty iron that I have given a good wire wheel brushing. The red primer really helps seal that clean iron and gives a smoother paint job.
'Hardener' is a product sold by automotive paint companies that makes the paint tougher after it dries. It also helps prevent gasoline from harming the paint. You can't save paint to which the hardener has been added. Make sure to save a bit of the paint without the hardener in it to use for touch up.
The key to a durable finish is curing time. I let mine sit at least a week between coats. I always use glass fiber filler for the first layer. You put it on a little rough and after six hours of drying I sand it with a rotating sander and 60/80 paper. After this, I take Polyester filler and smooth it up, two layers of spray putty then let it dry for at least a week.
The next week sanding, sanding and sanding again (you must have a lot of patience). When the engine body is perfectly smooth, I give it a last layer of primer and sand it with 600 paper. After spraying the engine with a quality brand paint, you can see yourself in it like in a mirror.
Whatever products you choose, make sure to follow instructions on the can carefully, as many of them have harmful fumes. Remember that all this advice comes from different people, and their own experience of engine restorations. Hopefully you will find some of the tips of use in your own restorations.
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