Another hot rod

The rear fitting used by the Race Department for the harness attachment was a bit of hardware straight out of the production car parts bin.

We sourced the correct hardware for the installation from a 1968 coupe, in which this fitting served as the revised attachment point for mounting the standard three point belt in MY68.

The MY68 donor had been built into a modern race car and had no further need for its old fittings.

The first image shows the fittings and surrounds as cut from the donor car.

The second illustrates how the parcel shelf of the hot rod was relieved for the fitting to come up through to the surface from underneath.

Next, the after fashioning the proper Race Department shape and dimensions for the mounting plates, the completed surrounds and to the fitting are spot welded to the bottom surface of the shelf. The shape and dimensions of these plates were copied from a 2,3L Kremer ST.

After finish welding the fitting and surrounding material, the installation is complete.

The Race Department fastened the ALU door skins to the steel frames with distinctive flat head rivets.

Unfortunately, the Race Department lacked the modern adhesives that we benefit from today and their use of rivets contributed to damage resulting from electrolysis caused by moisture combining with bare ALU on steel. The installation technique dates back to the days of ALU skins used on the doors of Type 356A Carrera GS/GT.

We had the benefit of examining a period ST door skinned in ALU to use as a "source document" for the placement and spacing of the rivets. This was a valuable research tool for duplication on the ALU skins for the doors of the hot rod.

The images attached to this post show an ALU skinned door from a factory built ST.

Besides the flat head rivets, note the drilled door hinge and hogged out interior panel, another extreme example of the Race Department's strict adherence to the Third Axiom - add lightness.

The door came from the same 2,3L ST that was written off in Germany in period, the same donor that provided its balsa front lid and plexiglas rear window for the hot rod.

It sat untouched for almost 40 years in a parts trove in Germany.

We used the old ST door shown in the prior post as a pattern for the positioning and spacing of the distinctive flat head rivets on the ALU door skins of the hot rod.

The fist image below shows one of the hot rod's door skins now in preliminary color coat. Note that the perimeter of the skin has been drilled so that the skins can be riveted to the steel door frames.

The second image shows the rivets arrayed in the same pattern as on the door we used as a source document.

As an historical aside, the shop tells me that this same installation is to be found on a few RSR that they have worked on as well as one genuine ST. They have also seen ALU door skins on ALU door frames on one RSR.

Guys who like hot rods always think their engines benefit from added oil capactiy.

The factory Race Deparment engineers were no different and enlarged the capacity of the dry sump tanks for the 2,5L ST and the Carrera 2,8L Competition Type.

While I am not aware of the factory building a big oil tank for the 2,3L ST, we decided that we liked the hunky look of the RSR tank hanging down below the rear fender line.

The shop had done this modification to the tanks of several early cars built for track use and the hot rod's original 2,2S tank was modified accordingly. As you can see the tank was sectioned to add material for greater depth and capactiy. While it was apart, the tank was baffled for improved oil control.

See pics attached.

very cool, 2 questions for you ;

1- did you have a stock of the flat head rivets or have you had them made ?

2- the rear harness mount on the parcel tray is fantastic , you are lucky enough to find these to use , hate to ask but is it possible to get some measurements so i can cnc some up for use in my project ? it's a bit hard in this end of the woods to find this stuff.

now thats an oil tank !!! i have a strange one that came with my car , but lots of capacity.

Hello John,

Beautiful fabrication on that tank for your 2,5L!

EASY is a very likely source to cut the harness mounts out from a MY68 parts car for your needs. They answer email and ship internationally. The contact information for EASY is in ESSES. Let me know please if they cannot help and I will look around as will other readers of this thread.

As to the "big head" rivets, in days past these were no doubt a standard item in a catalog of generic industrial hardware used by German manufacturers.

From what other board members in the UK tell me, big head rivets are now in the unobtanium category in Euroland.

However, these highly specialized, uber rare large diameter flat head rivets used by the Porsche Race Department for exotic applications, are in fact readily availble in the good old US of A right out of one of the specialty racers' hardware and fasteners catalogs!

cheers , i'll flick jim an email

The shop has done what they can to get the old balsa lid to align decently.

However, the concours enthusiasts among us will be snickering about the gaps...

Anyway, it fits pretty darn well considering it had a planned engineering life of a single race season. This one also survived a shunt that wrote off the tub of a 2,3L ST!

Considering that this grp bit is light enough to hang on a glider, and is now almost 40 years old, the manufacturer's know-how to make something this light last this long impresses the heck out of me. The lid has never warped, evidence that the factory had the proportion of catalyst just right in the resin.

Here is the final alignment.

Second image shows the outside surface of the old balsa lid in primer coat.

While I am told that factory built 2,3L cars were supplied with the same aluminum engine lid as the series produced MY70 and MY71 911S, this changed for the 2,5L car as the series produced MY72 911S reverted to the use of a steel engine lid.

However, a special ALU engine lid was included in the specification of the 2,5L ST as built by the Race Department for MY72. This special lid is sometimes referred to as "trim delete."

Here are couple of pics just to get oriented.

The first image shows the Kremer MY70 2,3L car at the Nurburgring. The raised lid not only has holes for the P-O-R-S-C-H-E lettering, it has the script installed.

Sometimes the lids in these old race photos will show the holes for the script under and around the taped-on Porsche lettering seen on most STs (and on the lightweight 70S in the last image below).

The second image shows a 2,5L car with the "trim delete" lid, devoid of the script and without trace of the holes drilled for their intallation.

The third image shows the 72 ST trim delete engine lid in ALU found for the hot rod.

The part number in the Modell 72 911S Spare Parts List for competition type shows the relevant part number as:

911.512.010.00 Declel hinten - Hood rear - Capot arriere - Cofano posteriore ALU

We will take a close look at the details of this interesting old lid in the next post.

The lid is not drilled for the script, but is drilled for rain guards and GHE rubber locks like the 2,5L car in the second image.