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Success in Painting Alum Engine Parts?

#41

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I spray-canned my last 440 build with Mopar Perf Engine paint (orange). The cast iron has held up very well, but the paint on the aluminum water pump housing has flaked off. As I'm getting ready to paint another engine, any tips for getting the paint to stick to the aluminum as well as the cast iron? Perhaps I need to prime aluminum?
 
Airplanes are mostly aluminum, I use what they use. I don't know how much heat it will take though.
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Regular paint will handle engine temperatures.
 
More important than any product you use, is to make sure the part is CLEAN . You can use 2k epoxy, but if the surface has some sort of contamination your screwed.

Clean , Clean , Clean. A good quality etch primer should be all you need , and follow with favourite colour .
 
I've used etch and epoxy. use grease and wax remover to clean, not paint or lacquer thinner. Single stage urethane car paint is the best. I have motors that were painted 20 years ago. This small block was painted 17 years ago. Aluminum intake, timing chain housing, water pump, and valve covers. Race motor 10 years ago. All aluminum except block and bondo filling pits.
Doug
Debbys Engine.jpg
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More important than any product you use, is to make sure the part is CLEAN . You can use 2k epoxy, but if the surface has some sort of contamination your screwed.

Clean , Clean , Clean. A good quality etch primer should be all you need , and follow with favourite colour .
This. Any metal surface MUST be clean, free of contaminants. No special prep is needed. A couple of light coats. My current non-primed, MP paint has been good for over 10 years now.
 
This. Any metal surface MUST be clean, free of contaminants. No special prep is needed. A couple of light coats. My current non-primed, MP paint has been good for over 10 years now.

The alum water pump assy was new from the box when painted. Paint flaked off within the first few years. Not so with the cast iron block and heads.
 
The alum water pump assy was new from the box when painted. Paint flaked off within the first few years. Not so with the cast iron block and heads.

New parts are almost always coated with an oil of some sort. There is no way of telling how long they will sit on a shelf. Last thing you want is to open up your brand new part and find it rusted or corroded ! .

Bottom line , paint doesn't stick for no reason. You painted both parts with the same paint, I am assuming at the same time. Yes one may be aluminum and the other iron but paint ( engine paint for sure ) should stick to both if they are clean.

I paint for a living , it can be a very frustrating process sometimes. We recently had a wave of brand new Honda's come threw the shop that had sat out dealerships back lot for months, due to Covid lockdowns. They got covered in tree sap that etched itself into the clear coat. They needed to be sanded down and repainted.

The catch , in their ultimate wisdom the dealership decides that they need to " detail" the cars before they come to the body shop. That means silicon / teflon spray for tires and trim pieces. They of course tried to remove some of the spots as well, or hide them best they could with waxes, glazes.

Needless to say , that stuff is a HUGE PITA to remove. Our normal prepping process , and cleaners did not do the job. 2 cars were done that were covered in fish-eyes before we got wax and grease remover with a more aggressive formula, and then followed by our regular products.

Nothing boils my blood more than standing in a booth after you laid down the clear coat, and watch imperfections literally just form right in front of you, and there isnt' a damn thing you can do about it !!!

I think what would be more helpful in your case is tell us maybe what you use to clean everything down with before painting.
 
New parts are almost always coated with an oil of some sort. There is no way of telling how long they will sit on a shelf. Last thing you want is to open up your brand new part and find it rusted or corroded ! .

Bottom line , paint doesn't stick for no reason. You painted both parts with the same paint, I am assuming at the same time. Yes one may be aluminum and the other iron but paint ( engine paint for sure ) should stick to both if they are clean.

I paint for a living , it can be a very frustrating process sometimes. We recently had a wave of brand new Honda's come threw the shop that had sat out dealerships back lot for months, due to Covid lockdowns. They got covered in tree sap that etched itself into the clear coat. They needed to be sanded down and repainted.

The catch , in their ultimate wisdom the dealership decides that they need to " detail" the cars before they come to the body shop. That means silicon / teflon spray for tires and trim pieces. They of course tried to remove some of the spots as well, or hide them best they could with waxes, glazes.

Needless to say , that stuff is a HUGE PITA to remove. Our normal prepping process , and cleaners did not do the job. 2 cars were done that were covered in fish-eyes before we got wax and grease remover with a more aggressive formula, and then followed by our regular products.

Nothing boils my blood more than standing in a booth after you laid down the clear coat, and watch imperfections literally just form right in front of you, and there isnt' a damn thing you can do about it !!!

I think what would be more helpful in your case is tell us maybe what you use to clean everything down with before painting.
^ This guy knows what he's talking about. Couldn't have said it better.
 
Painted mine with SPI epoxy primer and single stage urethane paint.
 
New parts are almost always coated with an oil of some sort. There is no way of telling how long they will sit on a shelf. Last thing you want is to open up your brand new part and find it rusted or corroded ! .

Hard to imagine they would oil new aluminum, but maybe they sprayed it with something else. It didn't cross my mind that I might have to clean brand new cast aluminum before painting it.
 
Always clean part's to be painted just like old part's. Zink primer on aluminum is the best thing to do. Use a heat base paint is a good idea. Sure they do treat new parts so they don't oxidize in the box.
 
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