FredR

My inlet manifold looked OK on the inside and I did not want to disturb it so shot blasted [with reservation] on the exterior surfaces after removing loose flaky paint sections that were falling off as invariably they do.

Things went a little wrong in that the blasting was a bit too severe for the relatively soft mag alloy- or so I thought. In fact what appears to have happened is that the blasting peened the surface of the metal so when painted it left a matt type of finish. four years on the paint looks like it did the day we did it. I also use a "dressing" on the surface that leaves "wet look" glossy type of finish that looks really neat. The trick with this approach is speed. This type of metal oxidises rapidly and I had the manifold prime coat painted within half an hour of the blasting process. The paint appears to have keyed really well on the surface finish that was left and we used regular cellulose silver paint of the type used on stock wheels. Although of course hotish, I do not think high temp paint is required. I suspect non of you have higher under bonnet temps than I do over here in the Middle East summer heat!



This approach might not appeal to originality purists but it is cosmetically very good and looks far better than stock.

jeff spahn

looks great

Herman K

In your case it was the peening that helped to anchor the paint so the key questions to duplicate this what was the brand and type of prime coat and finish coat used as well as what is method for applying the “dressing” and type of material that appears to give long term protection


This project is coming on my radar screen and I would appreciate as much information as you may be able to re-call.

Thanks

stevedavies

Malcolm, happy new year to you. I see you have started your intake refresh. I decided to leave my intake with the distressed Porsche look for the time being. Because I took my intake off so many times last year, it only takes me 30 mins to take apart now so no big deal to do a proper job in the future!

Did you see anything obvious when you took it apart to cause your idle problem?

dr bob

I need to learn that 30-min method, but don't want to go through the "many times last year" process to get there. Probably not happening that way for me though...

FredR

Herman,

I can find out the primer used but it is a stock Porsche cellulose paint system carried out at the local agents.

I do believe the peening effect helps the keying of the paint but the main reasons for the apparent success are the thorough blasting, the speed and the cleanliness. I believe we degreased the blasted surfaces with cellulose thinners immediately prior to priming. Once the primer is applied to seal the metal surface time is of little consequence I suspect. My epxereince with several of these things is that the problem lies with the initial preparation which I suspect was not adequate. As invariably the paint flakes off and leaves the oxidised layer expsoed, removing the top coat of paint probably serves little purpose.

The main caveat is the blasting. I had access to an industrial blasting facility that is used to prepare our large pipes that we use in the oil industry. I had no opportunity to experiment with different blasting media and the grit used was invariably too coarse, the blast gun too big and thus difficult to get into all the nooks and crannies thus resulting in overblasting of some of the surfaces as the operator tried his best to clean everything in sight on the external surfaces.
It was a case of "sh*t or bust" as it were.

If you can, start with a bead blasting technique to see if that will remove the paint. Either way you have to get all the original paint off and then deal with the oxidation layer [the black stuff]. You can tell when this is complete as the surface finish appears gunmetal greyish as opposed to black. One trick however is to use a final "sweep blast" when you have nominally finished the whole process to remove any oxidation that might have reappeared during the blasting process and then get the primer on within 30 minutes. Your local environment will also play a part depending on whether you are in a hot dry climate or a humid/salty one like [I suspect] on the Texas Gulf coast for instance. Speed in applying the first primer coat is thus of the essence.

I do stress that the peening effect [pock marks] that my manifold experienced would probably cause most to cringe. However, I was in the luxuriant position of having a spare manifold section.

If I can find the exact details of the primer used I will get back to you.

I have also seen my friends inlet manifold that was sent to the States for a professionally applied powder coating- I was not at all impressed and my friend was not too happy either I believe.

Regards

Fred R

Podguy

I send my manifolds and cam covers to American Stripping in Sacramento. After they come back I clean them with a little Pre and touch up any rough spots.

They do make a powder coat primer. I have used it to smooth out rough spots with good luck. However, I found a combination of two base coats of powder coating back to back followed by the clear coat does a good job of filling. It has been about six years and years and the manifolds still look good.

I did try some of the Metal Labs filler without good results. There was a reaction between the base powder coat and the filler. Some spots turned yellow. Best approach is to just powder coat the bare metal.

I find Columbia Coatings to have the best selection of colors.

I did the 85 manifolds in two colors. I used the powder coat masking tape and aluminum foil for masking. While I powder coated some of the interior of the manifold I would not do it again. Better to just mask off the interior parts. There was some improvement that could be made to the manifold for flow, but I forget now what those mods were.

Herman K

I've searched and found a lot of different approaches and read about other peoples experiences with painting versus power coating I’m leaning towards getting an extra manifold of a 1989 or later model that I can us for this refresh.

Thanks for all your information