Open Road

I started to write this up a couple years or so ago on the other place, but in light of how poorly some here were treated, I decided not to.

This tutorial will be kinda picture heavy, but hopefully well understood.

As all or most here already know the timing covers on the 968 are made of cast magnesium. (I don’t know if 944, 928, 911, etc are or not, but if so it would probably apply also.) And the covers are prone to corrosion damage. I have found a way to repair the original ones to near new condition. Here’s how I did it.

This set was sent to me by Raj. The 6mm x 1 threads on the cover had corroded away and corrosion had started on the exterior. First I filled the holes with Titanium Devcon and re-machined the holes.

While the Titanium Devcon was ok I wanted something better for the threads. Drilled and tapped for M6x1 Helicoil.

To precisely find the hole center I use a hole finder in a precision drill chuck on my milling machine.

Next, I bead blasted the metal clean of all the old paint. Then rinsed well in lacquer thinner followed with MEK.

This next step requires extra precautions to do safely because of the chemicals involved. Namely Sodium Dichromate and Nitric Acid.

Fresh air supplied paint suit shoe covers a gloves.

Follow the directions supplied. Brush on the Magnesium converter.


Rinsed in cold water and disposed of the waste water in the metal chip recycling bin. Seemed to be the safest way rather than down the drain.

Dried parts.

Next step spray apply DuPont Zinc Chromate primer. Same safety requirements as before.

Now it’s time to install the Helicoil inserts. I waited to do this at this time to make sure that the threaded areas of the cover had the maximum protection from corrosion with the converter and primer.

Time to put back the spring/alignment pins in the timing cover. They are 8mm so I used a 5/16 collet in the milling machine to gently compress them and install.

No black DuPont Imron available so used black Krylon out of the rattle can to finish.

The first one of these that I repaired was on my car. One of the bosses had completely corroded off. So I made a new boss out of Titanium Devcon and re-machined it.

I have more pictures of it around here somewhere. But there’s this.....

So, in summary, they can be repaired to near new condition and maybe more corrosion resistant than from the factory. I say this because I saw no evidence of any corrosion resistant coating when I bead blasted the old finish off.

Nice work. I did a 'repair' on my S2 a few years ago. Then other portions started to fail (bosses and warpage). It does make for a nice incendiary experiment though.

Got lucky and obtained a kit from Rennbay. Looks as though he has sold out the full run of parts.

https://www.pelicanparts.com/More_Info/ ... pn=RB104-9

Scott at Team Harco wrote: ↑Fri Nov 25, 2022 9:35 am Nice work. I did a 'repair' on my S2 a few years ago. Then other portions started to fail (bosses and warpage). It does make for a nice incendiary experiment though.

Got lucky and obtained a kit from Rennbay. Looks as though he has sold out the full run of parts.

https://www.pelicanparts.com/More_Info/ ... pn=RB104-9

Thanks. It was a nice project.

Had the new covers been available when I did mine might have gone that route. Makes me wonder why Porsche didn’t make them out of pressure cast aluminum to begin with.

Yeah - the weight savings came at a cost. Also, I believe magnesium can be cast in more intricate detail than aluminum.

For what it's worth, I did a write-up on the installation of the Rennbay kit over at TOS. In exchange for the 'advertisement', Travis sent the kit to me for free.