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Technical Engine PAINT failure

Discussion in 'The Hokey Ass Message Board' started by Jimmy2car, Apr 2, 2016.

  1. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    from No. Cal

    Maybe someone can help here?
    I think the mistake is ME, but need to fix, if possible.
    On my flathead engine, I painted the block and all attending
    cast iron items. NO problems.
    The cylinder heads are Canadian C7RA aluminum. I painted
    them the same using the same Duplicolor Engine Paint.
    The problem is that the paint is lifting as though water/antifreeze
    has gotten underneath near a couple of head studs. I can readily
    remove it with my finger.
    NOW, how to repair without removing the head(s)?
    What can be done? Better what did I do wrong that created the
    situation in the first place?
    ANY help really appreciated
  2. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,796


    Did you scuff and wipe with a tack rag before you primed them and before the color coats? Assuming you rattled canned them, rattle can paint goes on and works better if you follow the same prep as the real painters do.
    mad mikey likes this.
  3. tb33anda3rd
    Joined: Oct 8, 2010
    Posts: 15,149

    1. Connecticut HAMB'ers

    on aluminum i use an etch primer first.
    Paint Guru likes this.
  4. Preparation is the key;the surface has to be clean. HRP
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  5. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 23,444

    Jalopy Joker

    have recently had same problem with Dupli-Color engine paint on cast iron heads. going to clean off paint as best I can and switch brands and basically start all over again with pulling carb, etc because different brands colors do not match good.
    mad mikey likes this.
  6. anthony myrick
    Joined: Sep 4, 2009
    Posts: 4,567

    anthony myrick
    from al

    I have had very good luck with epoxy on properly prepped aluminum
    you mentioned you have studs so I assume there are acorn nuts
    remove 1 nut at a time and sand/clean prep for paint then re torque
    this will eliminate needing to remove the entire head and not cause any gasket issues

    just wondering why you would paint those cool heads?
  7. 39wagon
    Joined: Dec 13, 2008
    Posts: 26


    I would suggest that you scuff sand the heads to remove any of the old, non-sticking paint and then scrub the heads with a strong solution of soap and water to get rid of any heavyish oil residue followed by a wipe with a wax/grease/silicone remover like Prepsol. The sanding will also help give the heads "tooth" to help the paint to stick. If you have chrome acorn caps on the head bolts (where have I seen those before!), remove them and put in a set of dummy sparkplugs (so the good ones don't get covered with paint). A follow up coat of epoxy primer would be a good idea followed by a fairly heavy coat of enamel. FWIW, I've used a cheap brush-on paint like Osh's Eager Beaver brand on engines with success. But like any paint job, it's the preparation that makes or breaks the final product.
  8. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    from No. Cal

    Thanks everyone for the help and advice. I'll attempt to fix all this soon. I just knew it must have been something I did.
  9. Russco
    Joined: Nov 27, 2005
    Posts: 4,069

    from Central IL

    I quit using rattle can paint a long time ago. It sounds funny but I use brush on enamel with hardener (usually Van Sickle brand from the farm supply) and get much better results than I ever did with rattle can paint. The blue one is after about 2 years and several thousand miles on it and the red one I did in the car. Prep is still critical for either application though.
    344.JPG shoeboxeng.jpg
    Hotrodmyk and mad mikey like this.
  10. I agree! The enamel is really tough when prepped properly, and lasts a long long time.
  11. belair
    Joined: Jul 10, 2006
    Posts: 8,115


    Aluminum parts "absorb" oils. Got to get them really clean.
    moefuzz likes this.
  12. patterg2003
    Joined: Sep 21, 2014
    Posts: 532


    Degrease first really really well so you do not work any oil into the aluminum with sanding, scuff, Alumiprep etch, rinse with demineralized water if available & prime. Be careful to not touch the surfaces to be painted with any fingers after etching. If you have to handle the parts then handle them with a cheap pair of cotton gloves on. The demin water has no chlorides or fluoride in it that comes with city water. Bottled water is often demineralized so we bought some 5 gallon jugs. It is being fussy but it worked so we use it. Painted a lot of aluminum this way and it sticks. Quality of paint matters as well.

    I have seen the Cdn aluminum heads polished out and they look really good that way. Borrowed here courtesy of

  13. RICK R 44
    Joined: Dec 13, 2009
    Posts: 448

    RICK R 44

    As patterg2003 suggests, polish them they look great.
  14. 19Fordy
    Joined: May 17, 2003
    Posts: 6,463


    Bill Hirsch engine enamel is the very best. Brushes on real easy or spray. I used it on my flatty.
    Resists gas and is very durable. I brushed the engine shown 10 years ago and it still looks like new. I have never found a paint that will really work well on headers. Ceramic coating is the answer.

    Attached Files:

  15. flthd31
    Joined: Aug 5, 2007
    Posts: 561


    Strip the paint and buff them suckers up! I'm running those same heads. They're more paint problems

    canadian heads_0016.JPG
    i.rant, pat59, dan31 and 3 others like this.
  16. 19Fordy
    Joined: May 17, 2003
    Posts: 6,463


    Now that looks super nice!
    Subtle, but elegant.

    Not overdone. Just right.
    bobg1951chevy likes this.
  17. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,171

    from Zoar, Ohio

    Great looking engine. Is that rubber boots I see placed over the spark plug holes??? If so please explain? Thx.
  18. flthd31
    Joined: Aug 5, 2007
    Posts: 561


    Thank you. No, that's just the reflection of the black plug boot from that particular photo angle. Here's a different angle:

    Canadian Heads_0008a.JPG
    Jet96 likes this.
  19. Did you clean it yourself? I had the same problem on a 396. I trusted that the machine shop that cleaned it did a good job. It looked like it was grease free but it evidently wasn't. It flaked off with an air hose after it dried. Make sure you clean it really good just like you would a car panel before paint.
  20. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,951


    Canadian Aluminum heads were subject to many, many years of 30 below temperatures and often the engines lacked proper antifreeze.

    The Aluminum bulges up from expanding ice most usually from either of the center/two spark plug holes towards the closest bolt/studs underneath and diagonally from the spark plugs often times (but not always) heading centrally toward the central stud below and in between the two inner spark plug holes.

    Not saying that this is your problem but...

    If you noticed what you thought to be "casting lines" heading from a plug hole diagonally down to a stud, you wouldn't be the first to find that the Canadian Aluminum Castings had little/no imperfections and certainly No casting lines/marks.

    It may be a case of hot steam exiting once the engine is up to temperature causing paint to lift

    But then again maybe is was just preparation on the difficult to paint aluminum..

    But at at least you will now know what to look for.


    I wish you luck!

    moe in Santartica.

    Last edited: Apr 6, 2016
  21. T.L.
    Joined: May 24, 2011
    Posts: 206

    from Colorado

    I've always had very good luck with Dupli-Color Engine paint.
    Brush-on is probably better than spray-on though.
  22. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,951


    Very Good Point!

    One of the best ways to clean aluminum is using specific chemicals and Brass Brushes.

    Degrease the aluminum parts with gasoline etc.

    And while working in direct bright sunshine, place the piece in a large pan
    were the item can sit flat/stable.

    Pour in several inches of Bleach.

    Use only Brass brushes, steel will contaminate -Brass will activate.

    Scrubbing the item with the brass brushes in direct sunshine will cause a heat activated chemical reaction very similiar to (but the opposite of) anodizing or plating -kinda like 'unplating'.

    The dissimilar metals activated by the chemical/bleach will cause metal/electrons to outflow off the aluminum and towards the brass.

    The heat of the sun helps activate.

    What you will notice is that the aluminum part being scrubbed appears to turn grayish black.
    That is all the crap lifting out of the porous aluminum and depositing up above the surface.

    Once you have sufficiently scrubbed, You can use starting fluid, carb cleaner or brake clean to spray the lifted black from the surface. Use fresh/new brass brushes if needed but if you've done your job sufficiently, the carb clean/starting fluid will pretty well wash the grey/black lifted film completely off and you'll be left with about the freshest and brightest aluminum surface that you've ever seen.

    The after effects of Bleach on old intakes/heads and parts looks unbelievably bright!

    You may surprise yourself.

    Don't use bleach on installed parts or parts that have been anodized like certain carburetors.

    The intakes I scrubbed 30 years ago and clear coated (satin) in the sun lasted many years and the brass wire brushing left a nice factory grain (no lines) to the aluminum which allowed the rattle can Tremclad satin clear to bite and adhere to a decontaminated surface.



    mad mikey likes this.
    Joined: Jul 20, 2006
    Posts: 1,895


    I use DuPont (axalta now) self etch primer first. I did thi on the Olds engine in my rag top, and the paint still looks good. It was painted in 2000 probably. I did the same thing on the 350 engine I just built for the 42 Chevy I am building
  24. Yes indeed, on things like that I always wipe with a rag and acetone, then when dry, compressed air blow and tack rag after that.
  25. khead47
    Joined: Mar 29, 2010
    Posts: 1,555


    Consider the use of water glass to stop the coolant seepage first.

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