the flyin' scotsman

The intake paint has essentially flaked off and I have it off the car but we made a decision not to strip it further for a full strip and powder coat.

Question is what method is now best to pretty it up?

s928s

Need to remove oll the loose coating. Scuff up the surface and feather the edges. You could youe the hight temp engine paint. I have had success on serveral 928 and 944 intakes.

Lizard928

If you dont remove all the old material, dont bother.

the flyin' scotsman

Go big or go home?

Thats what I figured too.

GlennD

Last time I looked at the newer (87+) intakes, the coating was also flaking on the inside as well as the outside.
Have you checked yours for flaking on the inside? My worry would be that some of the flakes end inside the engine.

I have no ideas how best remove inside flakes.

Glenn

928 at last

Hey Malcolm!
Really, Check the interior. I just did mine. A true PITA. Time Love and several dremel SS wire brushes later( I already had the flexible extension set up).......we're in reassembly mode.
And, I had mine powder coated, so there was that to contend with too.
If you don't wnat to go the full on strip, I'd either go with Lizard, and just leave it be, or sand and brush, feather and spray (with high heat media) and hope for the best. Depends on the time you want to spend. I'm never going to be entered in a concourse event, so I probably overkilled, and it still isn't up to my standards.
Best,

928 at last

Actually, just had another look at the pics, and iyours looks really similar to mine when I pulled it. About the same in terms of flaking and overall appearance.......

JWise

I repainted mine in-situ on the car, obviously exterior only. When Sean and I did my intake refresh, I should have done it then but we didn't have the time. As I recall, the inside of my runners were gunked up pretty good, I theorize it should keep any flakes from falling off, LOL. Certainly didn't seem to harm my dyno results.

On the outside, I scraped off the loose stuff off and lightly sanded the primer to feather in any edges, then sprayed with Duplicolor Cast Coat Aluminum. It's holding up well so far, but it's only been one year and as Ed Ruiz would say - YMMV. I'm not ready to declare my method to be the best practice just yet.

Full write-up here: http://reutterwerk.com/forums/showthread.php?t=8804

SeanR

Several ways you can go and here is my preferred way.

Take a mouse sander from Sears, get as much down to bare magnesium as you can. If you have a media blaster use this for the spots you can't get to then wash the living hell out of it. Wash it, soak it, air blow it, stick a car wash hose at full blast in every spot you can get to. Then do it again. You don't want a single grain of media in there.

Now if you don't go the way of powder coating, clean it with MEK or something like that. Then take a high temp primer and coat it several times. I usually go 4 coats of primer (over kill I know, I also try to sand it down to fill some of the casting imperfections) Give it as many coats of a high temp paint as you want and then decide if you want to clear it. On a couple of the cars we did a clear and after a few months it started to yellow a bit. It actually looked pretty good, but was unexpected.

I did as Jarrod did with a yellow high temp paint, w/o stripping down and as of yesterday it's peeling. The magnesium will hold the paint better when you get it down to the shiny stuff and not the grayish stuff you find under the paint.

On the insides, get something that can grind/scuff/scrape in the trumpets really well.

mj1pate

If life is for everyone else the same as it is for me, there's scant time to go back in and redo work that could already have been fully completed. Bead blasting did not remove the coating on my 86.5 intake parts. I had to resort to help from someone with a cutting media, followed by a thorough washing out. I painted mine with high temp engine paint and clear coat, without primer (lack of experience). This was done several years ago and the finish is the same as when it was applied. A few scratches caused by carelessness were *very* easily covered over by brush touching-up with the same engine paint. I suspect that if you can locate a friend with a sand blaster, that a long lasting refinishing is a just $100.00 job. Good luck on the inside, though. The 86.5 tubes didn't seem to have any coating on the inner sides.

cobalt

This has been discussed so many times here on the 944 forums and the 911 early engine fans. They are all made of magnesium alloy. You will get decent results for a number of years by just cleaning and painting but if you want the paint to last for a lifetime, you need to do a chemical conversion on the magnesium prior to painting.

I recommend taping off all critical areas and then grit blasting the casting with a coal slag product like Black Beauty. This will remove anything given the correct pressures and leave a uniform surface. This should be followed by a chrome acid pickle per the requirements of AMS-M-3171 will work fine. Now you re ready to paint and have it adhere properly for a long period. The problem with the factory parts are they were never properly surface prepped and that is why we are seeing the coating separate after all these years.

BTW the factory used Zermatt Silver as the correct color, it has a tendency to turn goldish in color after time.

okbarnett

the intake and cam covers can be powdercoated and it holds up well . You have to take everything apart and have some one do it, but it turns out good.

Canuck928

POR-15 also makes a very high quality coating... www.por15.com

cobalt

All good products but nothing will stick to Magnesium if it is not properly treated first. Any of these coatings will make a hard shell but eventually it will crack or flake off no matter how good a product. Magnesium is a tricky material. That is why if you notice the paint from the factory does not wear off it flakes off in large chunks. This is what happens to any product including powder coating over time if it is not etched to allow the paint to bond with the surface.

Ask me how I know?

Jerry Feather

Thanks! I can pretty much guess how you know, but what I would like to ask is how you recommend etching the Magnesiun after it is sanded down to shiny metal and before it is powdercoated? Thanks for your help.

Jerry Feather