A Porsche for the Dirt Road

(updated 05/26/2001)

Why on earth would anyone want to destroy a fine sports car by sliding it around on dirt and gravel roads? I don't have a concrete answer to that right now, but I hope to soon!  After messing around with Unimogs for a few years and really enjoying the German engineering, I decided it was time to hook up with something at the other end of the speed spectrum.

Well, that's not my Porsche, and it's not Wyoming either, but it is a Porsche VERY MUCH off-road!  It's a factory 959 driven by Rene Metge to an overall victory in the 1986 Paris-Dakar Rallye.  I have that rallye on videotape and those 959s are fun to watch and even better for just listening to!  (I'm not sure exactly whom to credit for the photo, but I scanned it from a book written by Randy Leffingwell called "Legendary Porsche: Inside History of the Epic Cars.") The photo below is also from that same book. Mr. Leffingwell is the photographer.  

I had been toying with the idea of building my own "off-road sports car" from the ground up, with independent long travel suspension, mid-engine design, all wheel drive, light weight, and some serious structural rigidity.  The quality of our roads have done nothing but degrade since moving here.  Taxes go up, road maintenance goes down.  Typical.  Anyway, while the idea of fabricating my own chassis and suspension components was very appealing (lots of labor and next to NO material cost in comparison to labor,) the idea of building an actual car with doors, windshield, etc. was something I thought I might like to do a bit later in life.

Since I'd always been a fan of Porsche's desert rallye campaign in the mid Eighties, I started looking at a Porsche-based off-road project.  To be useful year-'round in Wyoming, all wheel drive was a definite requirement.  I'd need a 911 Carrera 4, available as early as 1989.  I wrote some influential Porsche people in the US and it was suggested to use the earlier 964-based 911 Carrera 4, since the five-speed transmission was more similar to the ones Porsche used in the factory rallye-raid cars.  The later 993 system (introduced in the USA in 1995) used a more transparent viscous coupling between the front and rear axles.

I starting looking for the right car to rebuild in 1998.  During the search, a friend noticed an ad in Hemmings Motor News for a real Paris-Dakar veteran!  It was a 3.2 Carrera which had been modified for the run to Senegal with Jackie Ickx at the wheel and Claude Brasseur navigating.  The factory designator for this car was a Typ 953.  The car was in Denver, about to be shipped to California to the auction block.  I made a quick 225 mile trip down to Colorado and was allowed to shoot numerous photos of the car.  Here's one...

That experience was just what I needed to boost morale for the project.  After almost two years of looking, I finally found a 1989 964 C4 in Minnesota.  The price was right and it had an almost complete documented service history since the original owner in San Diego.  Recently replaced were starter, clutch, climate control switch and some servo motors, tail lights, transmission seals, and the engine had also been removed and completely resealed.  The car had some minor mechanical problems, but they were just the right kinds of problems which I would deal with in the conversion.  More on that later.  I drove the car home and parked it on the lift, hopefully out of 'reach' of the Wyoming mice. I began inspecting the engine, drive train, brakes, suspension, and electrical systems, and also performed some routine maintenance while the car was on the lift.

The first project to come along was a lighting upgrade. Wild game is quite thick in Wyoming and I didn't want to turn my coupe into a cabriolet with a mule deer carcass!  I bought a set of Hella Rallye 4000 driving lights with my intention being to mount them to the hood.  To avoid destroying a perfect steel Porsche hood, I purchased a fiberglass hood from GT-Racing of Colorado Springs and swapped it for the steel unit.  Pound for pound, the weight stayed about the same.  The new hood was much lighter, but the Hellas put the weight right back on.  The Hella 4000s are heavy, well-manufactured lights.  Due to that, I didn't immediately see an easy way to install them.

I thought about the problem for a day and then starting building the light mounting bracket.  I wanted to make the transition from the sloped, curved fiberglass hood to the flat surface of the Hella mounting bracket and do it in a way that evenly distributed the load. Here are a few shots of the light installation, before painting...

(click to enlarge thumbnails)

These are wired into the high-beam circuit through a Bosch relay and 20A fuse.  They are 100W driving lights and really help out on our endless, unpopulated roads.  So far, the mounting system has performed flawlessly.  The fiberglass hood seems unstressed and the Hellas stay steady even in the roughest road conditions and with 100 MPH+ air against them.  (No lawbreaking here, now!  Speed limits are 75 in Wyoming, and it's nothing to drive into a headwind blowing 40 MPH!  

I also immediately changed the exhaust too.  The stock exhaust did sound okay, but not from inside.  Since I don't drive from the rear bumper, I decided to open things up a little so I could hear the beautiful flat-six sounds.  I removed the heavy stock primary and final mufflers and replaced them with a straight 3" pipe, exiting at the standard location.  The catalytic converter remains, keeping the car emissions legal.  It is loud, but no louder than the average glass-packed American muscle car.  I've been told this is considered a "Supercup" exhaust. 

With the exhaust done and lighting project out of the way (except for prepping and painting the hood) I now need to put some time into the engine, brakes and suspension.  I have new front and rear rotors and pads on the shelf awaiting installation, as well as fresh ignition components - coils, caps, rotors, wires, spark plugs, etc.  I am currently researching progressive-spring suspension systems that will provide 2" of additional height, to help clear the occasional rock or stump.  Slightly larger diameter tires (215/65-16) will generate another 1" of clearance.

To stiffen the chassis, a strut tower brace and full roll cage will be installed.  With no carpet or rear seating, RS door panels, Sparco Rev seats, and five-point harnesses will compliment the roll cage inside.  It has been suggested that I seam weld the car as well, to provide addition rigidity. That would truly be the ultimate, but since I don't plan to put the car through the rigors of competition, I have no plans for that.  

My wife and I are still contemplating a paint scheme, thus the gel-coat still on the fiberglass hood.  Currently, we're toying with the idea of using Rhino Liner spray-on pickup bed-liner on all of the lower plastic bodywork.  That stuff seems nearly indestructible to our harsh environment, and is very resistant to chipping and scratching. The only way I know to remove it is with a grinder!  When the plastic is done, I will also line the rear fenders from below, to help prevent damage from rocks kicked up from the tires.

To eliminate some maintenance issues and to make the car a little more interesting to drive on dirt and gravel roads, I will be removing the ABS and PDAS systems. The car will still be all wheel drive, but there will no longer be a computer able to lock up the rear and center differentials. Torque split will remain at 69% rear and 31% front at all times, regardless of slip.

The C4 and a real Oldtimer...

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