fraggle

For my cam covers, I ended up stripping the sealing surfaces, just because the newspaper and cardboard soaked through with stripper and it affected those areas. I used the wire brush and the pressure washer to clean up all the resulting flakes. We didn't re-coat those areas afterwards. Though Mine don't seem to leak at all.

I wish I could remember what I did with the end plates in more detail. Sorry!

Though I agree, it's still an open question!!

Ed Scherer

Thanks. That's very useful, too.

I suspect that there may be multiple different, but (possibly equally) acceptable alternatives to some of these questions. That's OK.

If enough people pitch in with "this worked, and this worked, but this didn't, etc.", that'd really put my mind at ease that all the questions have been answered to my satisfaction. And I'm hoping that this information, preserved in post #1 of this thread, will make it easier for everyone else contemplating this task.




I'm done for tonight, but will check back tomorrow morning.

I might just already have enough information that I can hand off my stuff to the PCer. He probably can't get to it for a few days, anyway. By that time, I can probably write up some guidelines based on this thread.

Thanks everyone for your help so far, and keep those comments coming. It's fantastic being able to draw upon the experiences of so many people here on Rennlist.

Jim M.

Ed, My insides of the intake and the cam covers had no coating of any kind when re-installed. Again, no issues 4 years later. I just did the GTS last summer although this time I rattle canned the paint do to a time issue. Both engines had large sections of the inside coating already missing and chips could be easily broken loose with an awl or screwdriver. Think about where all that coating went, down into the engine cylinders and the oil galleys. IIRC I read that Porsche coated the insides for better flow??? Long term IMHO it was a bad choice on the part of the factory. I did not paint the insides of the GTS parts.

When time permits, I will remove the intake on the GTS (want to do a little more porting) and this time I will PC. The rattle can paint job chips very easily, maybe the paint is to thick???

BPG_Austin

Ed, would you report your experience with the powdercoater as it progresses? Very interesting reading.
I'd be very interested to know how your shop strips the parts. (chem or media blast or both and with what media and pressure.) Also interested to learn how long they off-gas Mag and at what Temp. Where did you hear to off-gas for 24 hours? I have never heard of a shop offgassing for that long. (it would be a lot of cost from their end to run the ovens overnight) I just finished off-gassing parts at 475 for 3 hrs and there were still pinhole bubbles. its tough to get rid of them all. If you would share your findings it would be very valuable. Thanks.

Ben

Jim M.

Ben,

My PC guy baked the parts for 24 hours, at least that's what I was told. The PC'd parts are baked so there really isn't any additional run time for the ovens. His ovens were big enough to drive a VW into. All his parts were on racks when they rolled them into the ovens. Never had any pin holes in mine.

Earl Gillstrom

One thing never mentioned: "Pickeling".

After the alloys are cleaned, the bare metal will oxidize very quickly. I have used DuPont conversion coating 225S and 226S aluminum conversion coating on many parts with success.
The last few I used Columbia Prep & Paint. It seems to work OK and is much cheaper.

I suspect that some of the failures that I have heard of were caused by oxidation of the metal before the powder is applied.

I have also had the problem of not grounding the crossover to the engine block. Easy way is to sand off any powder from the mating surface of the 4 hold-down bolts.

123quattro

I've had a ton of stuff powder coated. The shop always masks off all sealing surfaces. When I get the parts back I use scotch brite pads on a die grinder to clean all sealing surfaces completely.

Also, don't get brake parts cleaner on a powder coated surface. It will "melt". If you don't touch it while it's wet it will reharden and be fine. To clean it I always use simple green.

BPG_Austin

Jim, that's really interesting. Thanks.

Ed Scherer

I've decided to delay another day (at least) until I can write up some instructions for the PCer.

I'll post an example soon.


Thanks for the additional information, Jim.

BTW, how are the insides of the intake media blasted? Seems like a lot of it would be pretty hard to blast media at.

Unless I hear otherwise, I think I'm going to specify full strip of everything as much as possible and leave the insides of everything bare. I'll update post #1 accordingly.

Will do, Ben.

You've probably already seen Jim's comments about the long bake.

I'll be curious what my PCer (I'm planning on using Industrial Coatings here in Kansas City, based on the advice of some local guys at the KCWS) will advise; when I talked to him on the phone last week, he mentioned typically using both chemicals and media blasting.

Interesting.

And what a horrible fate for a VW that would be.

I'll update post #1 to indicate the importance of PCing quickly (how much time do you have?) after cleaning before much oxidation occurs.

I'm going to recommend use of silicone flanged plugs (instead of simple plugs) for those holes. I hope the PCer is well stocked on silicone plugs, flanged plugs, and caps.

Good information; thanks.

RyanPerrella

if you find powder coating to be too much trouble, may i suggest.........PAINT!

when properly prepped it never flaked off the intake I did 4 plus years ago.

MUCH CHEAPER TOO

Like $50 in comparison to $350 (Less if you have your own blast cabinet, i did not)

Ed Scherer

Not too much trouble for me. I just like to be thorough.

Some of the same stuff (especially prep work) probably applies equally well to paint. But the masking requirements are obviously much more demanding for PCing.

Tom in Austin

Just to add to what Jim said ... the Brian Long book says Porsche added a 'plastic coating' to the inside of the GTS manifolds to 'improve airflow'.

When I did my intake refresh in January, the inside looked exactly the same as the outside, with large sections of the coated surface easily detachable like Jim's. Happily, I didn't see any missing areas that might have gotten sucked down into the engine, but that doesn't mean there weren't smaller bits that did come loose in the past.

(in case you're wondering, Sean has that manifold now. He cleaned up my old S4 manifold which I painted ahead of time to speed up the job. There wasn't anything on the inside of that manifold, either because it never had it, or because Sean blew it all out, don't know which ;-)

Probably one more good reason to refresh a GTS, just to check the condition of the insides and get any of that stuff out before it comes loose on its own!

Ed Scherer

OK, here's an example of what I'd like to document for each part (or part type). The target audience is the powder coater, so that limits the scope a little beyond some of the issues that have been discussed.

I believe that it's important to convey the most essential information efficiently, without a lot of extraneous information. And pictures are generally better than words. I'm sure these guys are busy.


Part Name: Intake

General Information

• Material: aluminum/magnesium alloy

Warnings!

(Note: I'd like to list anything really important here, like "avoid this kind of stripping chemical", or "avoid this kind of blast media")

• Coat this part promptly after cleaning; it oxidizes quickly.

Cleaning

• Strip all interior and exterior surfaces using chemical strippers and media blasting.
• Bake until you are sure all oils and contaminants have been outgassed.

Masking

Mask, plug, and cap using the following annotated photos as a guide.


Top view:




Bottom view:




Right side view:




Left side is mirror image of right side and is not pictured.

BPG_Austin

Hey Ed. I want to chime in here as I just did this whole job a couple days ago. Strangely familiar this is.. I used fiberglass tape to mask off the threads for the fuel rail studs. Tapered silicon plugs for underneath as well as temp sensor. You can either pull them before or after baking. I pulled mine before. I masked off the cavity for the flappy but I dont' see why you couldn't plug it.
From some research on a few pc forums, the basic principle seams to be that 'nothing good happens to a part after it comes out of the blast cabinet.' I mean the longer it sits exposed to air the more contamination it will absorb. My own, limited experience is that Mag will oxidize overnight. It comes out of the blaster appearing nearly white, but will fade to a dull grey after about 12 hrs. I've never waited that long to PC anything so I don't know how it would affect the finish. Blasting will remove, say 90-95% of the original coating. Thats just my personal experience and I'm learning a ton about this stuff. Its an artform. I'm really anxious to hear how your shop does and what steps they follow. Thanks for your write-up and continued updates.

Ed Scherer

Here's another one:



Part Name: Cam Cover

General Information

• Material: aluminum/magnesium alloy

Warnings!

(Note: I'd like to list anything really important here, like "avoid this kind of stripping chemical", or "avoid this kind of blast media")

• Coat this part promptly after cleaning; it oxidizes quickly.

Cleaning

• Strip all interior and exterior surfaces using chemical strippers and media blasting.
• Bake until you are sure all oils and contaminants have been outgassed.

Masking

Mask and plug using the following annotated photos as a guide.


Front view:




Rear view: