Smoothing cast alumnum for paint

Arrowhead

Oldtimer
I'm going to strip and repaint these valve covers but with a smooth straight finish. So I have a couple ideas on how to make that happen.

Use body filler to fill and smooth
or
Use polyprimer to fill and smooth
or
Die grinder to get out texture and then smooth w/ poly primer

Any thoughts?


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Can't see the pics either. I would smooth them with a die grinder, or better yet a buffing wheel with correct buff and emery compound. That would leave a finish that should be ready for epoxy although it wouldn't hurt to use some (used)80-180 by hand on them.
 
I'd agree to sand first. Can't see what style cover you have, (fins?) , but getting the metal itself smooth as possible first before priming should be the first step just as in auto bodywork. This includes hand block sanding both before & after primer to insure flatness. Buffing wheels & die grinders can be the best way to NOT have a perfect reflective finish if not done correctly. There is a hell of a lot of expansion & contraction on engine heated aluminum, so the less varying thickness of primer to fill it will give the most stable smooth surface. If compounding areas hard to reach by hand, stay with course compound, don't polish. I wouldn't use past 220 sandpaper either for best adhesion.
2k primer directly on metal would require a self etching primer under it to work on aluminum & hopefully not bubble up somewhere later (don't ask how I know), so it would be stupid not to at least start with epoxy primer if not all epoxy after cleaning with isopropyl alcohol based cleaner. 2k primer over epoxy would be ok, but no reason not to use all epoxy for blocking other than trying to rush drying to sand times.
 
Hey, a rectangle in a circle valvecover. :eek: Those must be pretty rare. Definitely worth restoring.;)

PS on most sites I have to upload from an account such as photobucket. On this site , I can go straight to photos on computer & hit open to post them.
 
Ugh still not working eh? Been posting pics on forums for years and never had problem. Everything was on Google "picasa" and Google dropped it and migrated all my pics over the Google "photos" and now I cant't figure out why pics won't post.
 
might be you're doing it wrong for THIS site
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I just clicked upload a file & recent pics came up straight from my computer. Clicked on the pic I wanted & hit open, then you had the image size option & done. No middleman site. Tried it just to be sure, not trying to hijack your thread with my pics.:D.
 
Thanks JL, didn't even know we had that option on the new and improved SPI forum. Did a little research and turns out direct links to pics isn't supported by google photos so that why it won't work anymore.

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Those are cool covers also, though not as rare as the rectangle in a circle ones. I still say final block sand all you can by hand to ensure flatness before epoxy priming. I'd also consider just leaving the texture on the sides of the letters , as this would be truly tedious to remove & not mark up the surrounding flat surface, though it could be mostly done with small round sanding discs as long as no part of the holder protrudes past the paper. Sand the letter sides first if you do so. straight carbide burr bits with and without an end cutting face could be used around & between the letters, preferably at a lower & more controlled speed..
Pretty sure I've seen those smooth in black before with the raised letters polished.
 
Well that was easy. Turns out most of the texture was in the factory paint. Same paint that was on the block (brand new GM crate 572). Once I stripped it, the actual castings were pretty smooth. Couple coats of poly and the texture was gone. I could have called it good, but after block sanding a few low spots showed up so another round of priming and blocking and they were nice and flat.

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Well that definitely added a few levels of class to those covers. That 2nd round of blocking looks like it was well worth the effort.

Been thinking about making me some ls engine fake valvecovers with that style of angled top and just painting them, as keeping aluminum polished sucks.
 
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