Questions on painting plastic engine covers

I

Inzane

New member
Hi There folks,

I'm planning to paint my throttle cover and upper timing belt covers, and maybe even my upper radiator fan shroud. I'm going to attempt this myself, not having done any real spray painting tasks before.

So far I have:
a multi-pack of wet/dry sandpaper of 320/400/600/800 grit
a can of Dupli-color adhesion promoter
a can of Dupli-color sandable primer (black)
a can of Dupli-color 500degF engine enamel (gloss black)
a can of Dupli-color 500degF engine enamel (clear)

I figured from all my detailing supplies I probably have enough degreasers and all-purpose cleaners already that I can try for initial prep. Unless, is there something very specific recommended for cleaning prior to paint?

From my list above, do I have everything I would need? And tips on how many sanding steps I should undertake and when?

Also, the two cans of engine enamel have been sitting around for a while. I bought them a few years back in anticipation of this project but hadn't gotten around to it until now. Should they still be "fine" or does rattle can paint expire at all. These cans have not been used yet and were stored indoors at room temperature.

I appreciate any other tips you may have. Thanks.
Jason

PS - There was a guy on either this forum or the old autopia.org that had a really nice painted engine cover on his pontiac grand prix, which he had done himself. Does anyone recall who that person was and whether they are still around here?
 
I don't know that I'd use engine enamel personally. If these are plastic covers on an engine they'll never see any level of heat that is that extreme. I'd use an adhesion promoter, a sandable high fill primer, and a base/clear combo personally. You can do a lot with color, and short of the base block/head/exhaust manifold the components don't get past 200deg for the most part. An idea, here's one of mine:

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Are you trying to go from a textured plastic to a smooth finish? Sanding plastic isn't exactly a easy thing to do depending on what type of plastic. You can actually just end up just scoring the surface really bad and you'll end up with the surface being somewhat "fuzzy" if you know what I mean. Like I said though, depends on the type of plastic. I'd maybe try a test spot on the under side first to see how it reacts to the sanding.

If all you're going for is just adding some color, just clean it very good (no abrasives) use the adhesion promoter (less is more in this case, just a dusting of adhesion promoter), once that dries hit it with your color and call it a day.

If you are going for a smooth finish on textured plastic, you may want to look into some of the plastic repair products that 3M sells. I'm unfamiliar with names but they do have a product for plastic that is used like body filler (bondo). Its a 2 part glue like thing that uses a special mixing nozzle to apply. If I recall to prep you would first sand the surface, then apply it to the plastic, spread it with a spreader (smooth it out as best you can) and allow it to dry/cure, then proceed to sand it smooth. Get it to 600 grit (no higher or paint won't want to stick) and then use your adhesion promoter followed by your paint.

Its been awhile since I've been though the body shop courses I took in college as well as my short time working in a body shop so some of what I've said may be outdated or missing points. I'm sure someone will correct me if I'm wrong
 
My grades of wetsand when doing trim parts are 1500/2500/3000....I'd rather sand a bit more than rotary out rough sanding marks.....
 
Quite frankly, I used plast-dip (a product I pretty much loathe) to do a plastic engine cover and was surprised how good it came out and how well it's holding up.

I used it because I was lazy and it was all I had on hand - except spray paint ( which I loathe almost as much as Plasti dip).

So, if your looking for fast, easy, and cheap - Plasti dip may be the way to go.
 
ShaneB said:
Are you trying to go from a textured plastic to a smooth finish? Sanding plastic isn't exactly a easy thing to do depending on what type of plastic. You can actually just end up just scoring the surface really bad and you'll end up with the surface being somewhat "fuzzy" if you know what I mean. Like I said though, depends on the type of plastic. I'd maybe try a test spot on the under side first to see how it reacts to the sanding.

If all you're going for is just adding some color, just clean it very good (no abrasives) use the adhesion promoter (less is more in this case, just a dusting of adhesion promoter), once that dries hit it with your color and call it a day.

If you are going for a smooth finish on textured plastic, you may want to look into some of the plastic repair products that 3M sells. I'm unfamiliar with names but they do have a product for plastic that is used like body filler (bondo). Its a 2 part glue like thing that uses a special mixing nozzle to apply. If I recall to prep you would first sand the surface, then apply it to the plastic, spread it with a spreader (smooth it out as best you can) and allow it to dry/cure, then proceed to sand it smooth. Get it to 600 grit (no higher or paint won't want to stick) and then use your adhesion promoter followed by your paint.

Its been awhile since I've been though the body shop courses I took in college as well as my short time working in a body shop so some of what I've said may be outdated or missing points. I'm sure someone will correct me if I'm wrong
Click to expand...

Good point. Is this textured plastic that you will be making smooth? If not you can lightly scuff the surface and paint right over it and be done. You will retain the texture this way.
 
ihaveacamaro said:
I think your grits might be too low...
Click to expand...

When prepping for paint you don't really need anymore than 600 grit. Final sanding before paint is 600. Any finer and the paint doesn't have enough to "bite" into and wont stick.

Now for sanding the top coat for highest shine? Yeah then you go higher. But paint needs a dull surface to properly adhere
 
ShaneB said:
When prepping for paint you don't really need anymore than 600 grit. Final sanding before paint is 600. Any finer and the paint doesn't have enough to "bite" into and wont stick.

Now for sanding the top coat for highest shine? Yeah then you go higher. But paint needs a dull surface to properly adhere
Click to expand...

Yeah I meant for after paint is on and before clear. I always like do like 1500 in between the paint and clear
 
ShaneB said:
Are you trying to go from a textured plastic to a smooth finish? Sanding plastic isn't exactly a easy thing to do depending on what type of plastic. You can actually just end up just scoring the surface really bad and you'll end up with the surface being somewhat "fuzzy" if you know what I mean. Like I said though, depends on the type of plastic. I'd maybe try a test spot on the under side first to see how it reacts to the sanding.

If all you're going for is just adding some color, just clean it very good (no abrasives) use the adhesion promoter (less is more in this case, just a dusting of adhesion promoter), once that dries hit it with your color and call it a day.

If you are going for a smooth finish on textured plastic, you may want to look into some of the plastic repair products that 3M sells.
Click to expand...

Its a bit of a mix. The timing belt covers and fan shroud are basically smooth plastic. The throttle cover is slightly textured.

I'd like to at least reduce the texture a bit, if not completely remove, but that's not critical. The timing belt covers, while smooth plastic, have minor pitting and/or light scratches that I'd like to try to smooth out as much as possible too.

I'm hoping the "sandable primer" I mentioned above might have some slight filling properties that will achieve most of what I'm looking for.

These pieces are for a VG30DETT (90+ 300ZXTT), in case any of you are familiar with that vehicle.
 
Your sandable primer will probably be all you need then. Just clean the surface really good, use your adhesion promoter, put on a couple thick coats of sandable primer (not so much that it runs), sand to 600grit, if you went thru the primer to bare plastic, dust it with adhesion promoter again then go straight to color
 
Did this one with automotive paint a few years back. Cleaned, scuffed with grey scotchbrite, cleaned again, adhesion promotoer, paint, clear.





 
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