DonaldBuswell

The 'charcoal' coating...never seen this before, and yes, the factory coatings are indeed seemingly twice the thickness as the S4

GregBBRD

Terrible stuff to remove. I can't find any "outside" vendor that can remove it, without ruining the manifold, so I end up stripping these manifolds, myself.

Takes me an entire day....which makes powder coating a GTS intake much more expensive.

The outside is tough, but wait until you work on the inside, to get it out of the runners! (Yeah, that really does need to happen.)

Pretty sure it's an epoxy coating in which the intake was dipped, since no chemical stripper seems to touch it and the thickest stuff is on the underside, in the corners.

The "charcoal" is the magnesium deteriorating.

DonaldBuswell

Any good media blaster 'should' know when things can get wonky. Sitting there blowing blasting media onto something like this GTS coating means the blaster can not really tell when it's all off the substrate. The blaster can wear it down to a few microns, and, if his glasses are not on, or his lighting is bad he (or she) will deduce that it's good to go! On this manifold I will be breaking up the coatings by hand, then blasting it clean and finding remnants to then remove. I wonder how deep the Germans applied this coating; ie down each intake plenum chamber in the same thickness as the outer sections that are visible? I will continue to post my results. Another thing is too sharp a media will certainly cut into the coating, but, it will certainly be cutting deeply into the metal substrate - something to avoid, thus some good brand new plastic media will do the task!

Mrmerlin

As Greg said these manifolds are dipped into some type of epoxy coating so the entire manifold is covered in this stuff/
To remove the coating from the inside its best to use a MAPP gas torch and a long stem bent thin screwdriver.

NOTE work on a metal table and work outside, the torch wont light the manifold on fire, but have an extinguisher handy for magnesium fires
NOTE you dont need to hold the flame on the area any more than about 15 seconds,
this softens the coating then a screwdriver tip should catch an edge and pull off a piece.

cobalt

Have you tried acid strippers first? Porsche never chemically converted their mag parts with a DOW coating current spec is AMS2475. Even a simple acid pickle DOW #7 would have helped preserve the magnesium and give it a better surface for paint or anything to bond to. I would caution you the grey powder that forms on magnesium over time can be explosive when media blasting. Overall the condition appears to be excellent for the age. I used to have a pangborn walk in media blaster house 10 x 14 feet with 5/8" nozzle and 90 PSI using black beauty coal slag I have no doubt it would have little issue removing this.

MrLexse

The epoxy coating on the GTS intake manifold is inside the runners and it is seemingly impossible to get it all. I also suspect that chips of the GTS coating come loose during normal operation and end up in the cylinders. I remember renting a huge commercial sand blaster by the hour years ago, just to try to strip my GTS manifold of it's coating. If I remember correctly, I was at it for three or four hours before accepting the fact that I wasn't going to finish it and that I wasn't going to be able to clear the intake runners except by chipping by hand. I could (and have) completely stripped two S4 manifolds in that time with no worries about the coating inside the runners. If there aren't any meaningful dimensional differences between the S4 intake runners and the GTS runners, best bet may be to just swap the GTS manifold for an S4 manifold.

SeanR

LOL, this is the reason I sent one to Donny when he said he wanted to tackle one. The one he's got here in the vid is not as complete as the one I sent him so this should be fun. I figured why not, if Dr. Blast can get the coating off and do it to the level I'd love to have done I'll send him the other 3 I've got to work on. These GTS intakes suck to do. Can't say how many hours I spent chipping/grinding/etc to get one clean, which is why I have a few of the GTS ones as I keep using S4's as replacements.

Mrmerlin

I spent 12 hours with my Mapp gas torch and a long bent screwdriver cleaning the inside tubes of a GTS intake, about 2 to 3 hours a day for days .

buccicone

Looking at doing this in the coming months on my '93. Is the cam/valve covers coated in the same epoxy on the GTS?

DonaldBuswell

Cobolt said the gray powder is explosive when subjected to Media Blasting? Humm...this may be 'fun'. However, I don't use Black Beauty media, it's horrible stuff, far too aggressive for anything, it would significantly change the dimensions of the manifold, meaning wear out flat edges for gaskets to mount to, and when I blast PSI has nothing to do with my lane; I'm all CFM, I'll run around 30-35 PSI on this Intake. I've chipped a lot of it off already. Blasting will lift much of it off by getting underneath the segments. Lots of cracks in the coating but it's not really adhering too well to this substrate. As Stan said, and GB said, the insides of the runners will be challenging. However, there is a LOT of inconsistent thickness of coatings, and the intakes deep inside I bet will NOT be as thick as the air horn ends' thickness is.

GregBBRD

Yup, bring a sack lunch and spend the entire day. Come back again tomorrow to finish. And I'm 100% certain that the heated epoxy paint (or whatever it is) is a real health treat....what could possibly go wrong with breathing in something completely unknown? (I will not allow my guys to do this job...I do this, myself.)

And, of course, the GTS owners expect to pay the same amount as the S4 guys do, for the whole job....

You only make that mistake once.

GregBBRD

You would not believe the number of late model 928 manifolds that I've had ruined by strippers/blasting people.

Not yet ten, but damn close.

I'm not really ready to suggest to these people that they use an acidic stripper.

DonaldBuswell

Usually, something we undertake that makes it easier/faster up front has a negative effect on the other end, this is law, Hermes told us this in his laws of Correspondence, Rhythm and Cause and Effect. I have used a chemical stripper 3 times in 12+ yrs prior to media blasting. It is such a mess and does not really help at all as blasting still has to occur. The strange thing is that plastic likes to have something to bite into, after a chemical strip the slime needs to be removed and, it took longer to remove the filmy residue by blasting than if I just media blasted it from the start. This GTS manifold has lots of areas where adhesion has failed and the only factors keeping it 'on' is the bond it has with itself in the form/shape when it was applied, so chipping it off is moving quickly. I'll try that torch today, outside...I do not like breathing strange things, I got my lungs full of that crap in Desert Storm and Iraq in 2004, but the second time around we didn't burn our poop! Oh today's soldiers don't know the joy of dragging a 55 gallon drum out, and burning it all up!

cobalt

I hear what you are saying. I am familiar with mag parts and the nuances. I spent thirty years in the foundry business manufacturing magnesium and aluminum sand castings for the aerospace, DoD, and commercial applications. Third generation foundryman and my Grandfather was the head of the Bendix Eclipse Pioneer program from 1930 to 1955. His R&D was released during WWII reducing scrap by 40% nation wide. He worked with Igor Sikorsky and every major company Including Dow metal. Pioneered AZ92aT6 and most of the Dow coatings and extensively researched media blasting. I have volumes of studies on different media done by him and the potential explosion issues. It doesn't matter what media is used unless it was shot peen which is a near certainty and another common mistake many make is not grounding their equipment. I used black beauty exclusively since it removed very little material <0.001" on average when you don't dwell on a specific area and breaks down on impact. I had to be concerned with tolerances but my parts were raw castings. Agreed you would not want to blast any machined surfaces or tape them off if you did. This removed the oxide layer and opened any imperfections for subsequent Penetrant inspections 100% of my parts were inspected and most radiographicly. My field was castings and not blasting that was just a support to my product and preparation for inspection and preservation. I would consider a Dow coating or chemical conversion prior to any finishing. I have many mag automotive parts made for vintage race cars now going on 25 years without any issues of paint peeling or corrosion that are exposed to the elements quite often in vintage racing.

BTW my blaster had a 1000 gallon tank reserve and I don't recall the CFM but it was significant and it would run my 12" piston American air compressor constantly or 2-50 HP Kellogg american hydrovane compressor simultaneously at full duty. I would also consider a bath to remove any residue if acid stripping followed by drying in a circulating oven at around 120 degrees F blasting would never work and only stick the media to the part. I would also be careful with Map gas on mag parts especially if they have grey powder. Another rare occurrence but it could ignite, If the part were more structurally critical it could destroy any temper as well.

Interested in what you come up with. I have crack forming and was considering redoing mine soon.

DonaldBuswell

My first 5 minutes of blasting back in 2002 I noticed some static electricity, since then, I ground everything including the reclaim lines carrying spent media back for recycling. Black Beauty is brutal, absolutely not needed for anything I blast. My Plastic does a very good job.