Someone in the past oversprayed the ceramic coil box posts black. I sanded as much as I could get off but it is porous and looks grungy white now. Is there a way to get them white again by cleaning or do I have to just paint them white?
Ignacio, try some paint stripper. Dave
When you strip them,then put them in Bleach for a couple days.
I always heard it was a bad idea to sand or even scuff up the protective coating on porcelain because it looses its insulating effectiveness. Not sure if this is true or not, but i always follow what i heard, till proven wrong.
The later porcelains were not coated. The glazed ones are on the earlier brass cars.
Try using household cleansers like comet or zud. They are made for cleaning porcelain sinks, toilets and tubs.
These are typically unglazed porcelain. Scuffing or sanding will not
alter them electrically.
A couple day long bath in muriatic acid will loosen just about any dirt
and crud, paint, soot, or aoli tartar sauce. Will scrub clean with a tooth-
Repros are also available: https://www.modeltford.com/item/5005.aspx
Unglazed coilbox insulators can be effectively cleaned by bead blasting at 40 lbs pressure.
John N, That is true depending on certain circumstances.
First, any porcelain that has a shiny finish glaze (like most spark plugs) should never be sanded or scratched because even a microscopic scratch can allow a high voltage pathway to develop. This is the reason they began glazing spark plugs around 1903 (I believe that Henry Ford had something to do with that?). Some spark plugs were unglazed well into the '20s. They are usually fairly rare, because they usually failed early on.
Next. The porcelain does not HAVE to be glazed, as long as there is enough of it and other non-conductive air space (DRY wood) etc to prevent a high voltage path.
Next next. Lower voltages like timer connections, battery supplies, and even a magneto putting out over 40 volts AC at 50 mph are not critical.
Ford used glazed porcelains on coil boxes during the brass era cars, well into 1915. Late '15 model Year on, the coil box porcelains were unglazed. Ford basically decided the glazing was not necessary due to other resistant distances. And he could shave pennies off the cost of the car by not glazing them. Apparently, he was right. The later cars rarely have issues from that. And when they do, the trouble is usually wet wood. Glazing the porcelain insulators will not fix wet wood.
On the unglazed insulators, mild sanding with fine (finish with very fine 400 or more), should work okay. Earlier glazed insulators should never be sanded, But they can be cleaned somewhat using glass-top stove polish (or most fine glass polishes). Bleaching stains on the unglazed insulators should be okay. I have tried it a few times, with varying success.
Always use four of your best looking (no stains or cracks) insulators on the plug wire positions of the coil box. I actually have used broken insulators in low voltage positions by gluing with clear epoxy and even built up a broken corner once. I put the flaws where they show the least, and never had a problem with them. (As long as they stay low voltage!)
What else is made of white porcelain that might need whitening? Dental crowns and dentures. For the final cleaning, try some stuff that is used for teeth.
To get the paint off soak them in lacquer thinner and scrub them clean with a small brush, like cleaning a paint gun.
Lacquer thinner and a small brush worked for me. You can clean them up pretty well but they wont be as pearly white as the glazed smooth finish on the older ones are. That slick finish does a little difference.
Like to use the foaming denture tablets, if it can clean false teeth, coil box porcelains can be brightened too! Don't use steel wool, it will darken the porcelain.
Before soaking overnight, 2 or 3 tablets as you want them to do their best. Anywhere pharmacy stuff is sold they have boxes of these tablets.
After, some come out better than others, but at least it does the job!
I've never been satisfied scrubbing, soaking and fretting. So I now just hit them with brake clean and flat white spray paint. They come out like new!
I prefer using the glass ones.