Ok, got my block all cleaned up and brushed with phosphoric acid to kill any last bits of flash rust. I'm reading a ton of posts from folks and it seems half the people use epoxy primer and half use etching primer. I'd like to hear from people that have used both and hear what they have to say. By the way, either primer will be spray can. I will also be painting the aluminum intake, if that matters as far as which primer would work best. This is not a trailer queen, this is going on a car that will see a LOT of miles over many years, so durability is of utmost importance. Posted using the Full Custom H.A.M.B. App!
I use no primer, and use acrylic enamel paint. This way, when it goes wonky in a few places (chips, flakes, heat etc) you don't see primer.
Rustoleum self etch primer is the same as the "real deal". I have found it to be incredibly tough. Tried to remove it with brake fluid and it wasn't affected.
I have been painting my bare blocks with acrylic enamel for years,no primer used. Actually I have painted the last few with a brush. Enamel with hardener flows out like gl*** on an engine block.
Watch the interaction with the phos acid coat and your next coat. Some react in such a way as it appears as though the treated metal spits the primer off like spitting a watermelon seed. Real Epoxy prime can be had in spray can, it has a internal tube of activator that you need to break and has a few hours life. No tube and its junk usually.
I was thinking about the possibility of a reaction, which is leaning me towards an etching primer, since that already has phosphoric acid in it and would be less likely to react. I know I can get Rusto pretty much anywhere, how does it compare to SEM or Sherwin Williams 988? Posted using the Full Custom H.A.M.B. App!
I scrub the hell out of the block with soap, water, and then lacquer thinner until it is spotless. Then I apply epoxy primer (2-3 coats) and then top coat with my favorite paint (which happens to be Imron). Never chips, never fades, washes like a car body. Don
I've been using endura primer sealer, on engine blocks I get it all cleaned up etc, once in the bay I give it a good spray down with clean gun wash let it dry completely. Lay the primer an color with the work time usually in under an hr lay top coat and you've a block that will take 300 thou plus worth of miles of abuse with any trouble. I have 2-3 complete engines still looking great. Posted using the Full Custom H.A.M.B. App!
Whatever you prime it with be conservative with it. A nice thin coat to promote adhesion. SEM is bulletproof over aluminum and really makes the paint stick. Hard to get off too. I used to do all my race stuff in semi-flat black. All I did was clean to the max, wash with lacquer thinner as a final cleaner. Just before I painted I sprayed the block with thinner again and applied the paint as it was flashing off. The idea was to 'stain' the cast iron vs actually paint it. Krylon semi-flat was the best. During a rebuild I stuck the block in the hot tank and most of it was still there and lookin good. The POR-15 I painted all the valley, inner crankcase and timing chain with looked new after over 400 rounds and the hot tank cleaning. For restoration I sprayed a thin coat of DP epoxy (not DPLF) then 2 lovely wet coats of single stage reduced an additional 25%. The last one still looked new after 22yrs.
I second that. I cleaned down and then sanded everything down before etch primer and then colour. Cleanliness is the key. I also changed the output shaft and extension housing.
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