Opel and Vauxhall built 4 proto type rally cars, 3 Opel Kadett Rallye 4x4.. 2 went on to do the 1986 Pari to Dakar and 1 Vauxhall Astra 4S that was entered and finished 4th in the Audi Sport rally on 11th Oct 1986 in the hands of Andrew Wood/Mike Nicholson. After this one of the Opel Dakar cars went to John Welsh to compete very successfully in the English Rallycross Championships.
I have found references to 4 configuration engine in the car:
2.4L Manta N/A Engine: 250HP
2.4L Manta Supercharged Engine: 325HP
2.4L Manta Turbocharged Engine:400HP
1860cc Zakspeed Cosworth Turbo Engine: 500HP
This was mated to a 4WD gearbox called Xtrac System. Mike Endean Formed Xtrack and designed a 4WD gearbox that could be changed by hand while competing from 28:72 (front:rear) drive stepless to 50:50 by a hydraulic system.
This was all packed into the humble Opel Kadett GSi and is reported one version was as light as 850kgs. The car retained the floor and roof and pillars of the cockpit and the rest was space frame and sheeted in fiber glass and kevlar.
The Replica I am going to build will be the "Andrew's Heat for Hire" Sponsored Vauxhall Astra 4S as it was presented for the Audi Sport Rally in 1986.

This will be the 325BHP 2.4L Manta Supercharged Engine. This was, as all Manta/Ascona performance engines a Diesel 2.3l block re-bored to 2.4 and fitted a Cosworth twin cam 16v head. The Supercharger was a Sprintex and was fuel injected.

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History lesson over...
I have been working and researching this for quite some time. Last year I came up with a plan to build the car after recieving the fantastic news a person I know on the Mk2 Astra forums in the UK had been able to track down and obtained some of the original molds and panels from the 4S. This now makes the car and being able to get these panels will now make the car more of a replica than I had hoped for.
So looking at the speck of the car there are 2 main things to consider.
1st a 2.4l 4 cylinder twincam 16v engine. This is not as easy as it sounds. The best I could come up with is in Germany guys are making Manta replica engines from using a old 2.4l block from the Frontera 4x4 which is a cast iron block but not that easy to get a hold of. But even harder is a C30SE twincam engine that is a 6 cylinder and cutting 2 cylinders off and making a 16v head... they do it and it works a treat... but well it's a lot of effort.
I searched for ages and considered Saab engine bored out which actually only gives you just over 2.3l but very powerful. Then one day I found that the Ecotec engine we all know and love has a 2.4l VVT version made in America only... so this is it problem solved.

As you see above my 2.4l VVT Ecotec I have a M90 Supercharger adapted to GM's tricky water to air intercooled inlet manifold making the need of a front mount intercooler obsolete. A few other things where needed like lower compression from 10.4:1 down to 8.5:1 and H beam rods ect to give me an expected 350BHP.
2nd thing is the 4WD system. It has to be north/south engine config and be able to handle upto 400BHP. This left no doubt a Skyline 4WD system would be the best and cheapest.
So this week I took delivery of a Nissan R32 Skyline GTR. This I will strip and use all the running gear including the front and rear Multi Link Suspension system and including the 4 piston front and 2 piston rear brake setup.

So along with the Daewoo 15i shell I also have... I have the parts to start the build. All I need is the fiber glass panels from the UK and I have all the bits.
This car will be in the 380HP per Tonne range and 4WD, together with the car being balanced with the engine almost behind the front struts and having a 4WD weight displacement... it will be very neutral.
For traction I will retain the ATTESSA 4WD System from the GTR... So it will launch like a GTR but weigh 500+ kgs lighter and the Supercharged 2.4l will have no lag and heaps of torque.

For more info about the history of the car you can look at my unfinished wesite with plenty of info and pics. Plus some of my others cars and some more on the Opel Kadett GSi rally car as well.
http://www.ynet.com.au