The build of a rally car - tarmac, open Class

[AlexJ]

After my first restoration project, http://forums.pelicanparts.com/porsche-911-technical-forum/556994-yes-forward-but-different.html, I decided to go with the build of a rally car to compete on the local championship (Madeira Island - Portugal) which events are all tarmac.

Taking advantages of an Open Class, where Porsche components can be swapped between years, I started with a Carrera chassis and modified it regarding its purpose.

This car is not supposed to be a replica or what so ever but I decided to have a classic look, so it will be very close to a RS 2.7 1972.

Basically I will try to mix a classic style with some modern solutions regarding its performance.

This car was a parts car with a title which allowed me to sell some of them to get funds for the build on its new specs.

[AlexJ]

I started to clean and reinforce the chassis.

Surprisingly , this was a rust free body and no repairs were necessary.
So directly to the reinforcements:

[AlexJ]

... and some more criticas areas:

[AlexJ]

.... and some more...

[AlexJ]

After this stage all the panels were fitted to check alignments...

[AlexJ]

One of the main goals is to make this car light.

Fiberglass panels are: engine lid with Duck tail, bonnet and bumpers (front and rear).

After this first stage, all the body sealants were remover and epoxy primer applied.

The roll cage was supplied by Fennlane Motorsport and is fully welded on the chassis.

Here are some pics:

[obrut]

Alex,

Firstly, nice work. I have been tarmac rallying an early 911 for over a decade.

I know you want a light car, but I would strongly recommend using more roll cage than what you are intending in a tarmac car. Not trying to criticise but I have seen some bad accidents and trees are very unforgiving.

At the very least, I would cross brace your main hoop and run double bars in the door openings.

ps. Come down and do Targa Tasmania one day!

[AlexJ]

Also Plexiglass Windows will be used and the heating will be deleted.
To replace it, a heated windscreen will be fitted, which from my experience is one of the best options you can have on a rally car.

[AlexJ]

The painting has already started and here is the result:

(First the inner compartments, interior's etc)

[AlexJ]

And a few more details...

[AlexJ]

While the outside painting is being prepared, I have been preparing some other bits, in order to make the assembling process as quickshift as possible.
(I am planning to have the car nearly finished by the end of April - am I being too optimistic? No...... . )

Here is a set of instruments I have been restoring:



This is a mix from several gauges I had in stock - this doesn't mean to respect any originality but to be efective and provide the necessary information.

[AlexJ]

Hand brake is goingto be hidraulic:

[AlexJ]

I also restored the steering rack, fitting the necessary turbo tie rods...

[AlexJ]

The engine that I will use is a stock 3.2 with the following improvements:

- ARP con rod bolts
- reinforced valve springs
- oil pressure restrictors to avoid vindage on the cams
- titanium valve caps
- ROW Compression ratio 10.3

The engine is now being overhauled, replacing the critical items as piston rings, all gaskets and seals, chains, sensors, all the bearings (main and con rods), etc.

Soon I will publish some pics of the engine rebuild.

I decided to fit an EFI kit from a well known builder...

[AlexJ]

Even with this improvements, I am a little concerned about the RPM band I should use.
I have been advised that the 3.2 engine doesn't deal very well with top RPM improvements... so at this stage, Rev limit will be stock.

I already received the exhaust:



Rear muffler will be a stock one, modified to allow a better breathing.

[AlexJ]

Originally Posted by obrut

Alex,

Firstly, nice work. I have been tarmac rallying an early 911 for over a decade.

I know you want a light car, but I would strongly recommend using more roll cage than what you are intending in a tarmac car. Not trying to criticise but I have seen some bad accidents and trees are very unforgiving.

At the very least, I would cross brace your main hoop and run double bars in the door openings.

ps. Come down and do Targa Tasmania one day!

Thanks for your feed-back. I am also very concerned about safety. I can tell you I had some really nasty accidents on my 12 year Motorsport career... but in my opinion this roll cage secures the critical areas in therms of safety. After all, it compiles with the FIA requirements.
Roads here in the Island are very slow and I am entering an age that I don't think I will have anymore accidents.... kiding!
Thanks anyway for your recomendations!

[AlexJ]

Regarding the Targa Tasmania, that is an event out of my pocket!
That would be a privilege to be on such a big event but... Can't reach it!

[AlexJ]

Other thing I have been restoring is the pedal box.

On this kind of project, we normally see custom pedal boxes with independent brake pumps.
On this car I will keep the stock pedal box with brake booster.
I have been trying different rally cars with both systems and I really prefer the servo assisted ones. I prefer the feeling.

Here is the result of my pedal restoration, including the fit of a bronze bush set:

[Elombard]

Looks great.

Surprised on unlimited class you did not go to the shock towers front and rear with the cage. Regardless should be a fun beautiful rocket.

Another note, going with that intake set up did you consider cams with more overlap to take advantage? Or does the relatively low rev limit play into that decision.

[AlexJ]

Hi Elombard.
This project has a limited budget. Because of that, the solution you mentioned was going to cost much more. And the same time, I know that most of the rally cars here in Europe have similar roll cages to mine and from their experience, they work fine.

For the same reason mentioned above, cams will be stock.
That Efi system is recomended to 3.0 ltr. engine, max. As I'm keeping it stock, I still can use it without problems.

Probably next year, I will start building the 2nd. version of this engine.