917 at Snetterton !

[Marcus]

Allan,

the factory never equipped the 917 with roll cages or a fire extinguishing system.
It was Ferdinand Piech (by then head of Porsche`s Racing Department) who made weight saving the prime directive above anything else. It is said that he was somehow obsessed by that.
The John Wyer team upon their own initiative equipped their 917s with a Graviner aircraft type extinguishing system.
Speaking of Porsche`s obsession for weight saving: Not only did they some experimenting with Beryllium discs and pistons, but also for the sake of sparing the weight of the fuel pumps they ran a 917 with its rubber fuel tanks encapsulated in a pressurised titanium bubble, the latter being etched down to a wall-thickness of only 5/100 millimeters.

Marcus

[I LOVE GT40- Paolo]

12 cylinders?

I know someone in Maranello producing very good ones...will be cool to see a super fast Ferrari powered v12 917k

and surely it will be faster and powerful than the original porsche engine.

Just remind the difference in sound and speed approaching "parabolica" in Monza when Joest 962 arrived..and the THUNDER done by the MOMO 333sp...


seriously talking:
Graham, do u think can be possible to fit there inside a 12 cylinders as ferrari ones?(maybe from 550 or 575 serie..)

Thnx for the wonderful pics
Paolo

[Frank Catt]

Paul, certainly you have my permission to publish my in car video of Spa, it will readily show the real difference in performance between the two cars, and the ability of a real driver.

[Lynn]

Fred,

I noticed that no one responded to your question about the transaxle. You are right in that if you mearly turn everything around, you'd end up with 5 to 6 speeds in reverse and only one forward.

There are two, possibly three, solutions to this. One, which you alluded to, is to reverse the rotation of the engine. The early Corvair to VW dune buggies did this because the Corvair turned opposite of a VW. The main thing this requires are different cams, reverse rotation starter and, dependent on the engine used, possibly a modified oil pump and/or water pump.

Another option is to flip the ring gear so that it runs off of the other side of the pinion. This can be an easy solution; IN SOME TRANSAXLES. There has to be clearance for the ring gear to be flipped or, at least, the ability to provide enough clearance by machining the inside of the differential housing to allow the ring gear to be flipped.

There is a possible third option that comes to mind, but it is not clear to me if it is possible. With the installation of a non-911 engine with a 911 transaxle, utilizing an adapter plate like in a GT40, there is the opportunity to flip the transaxle in addition to turning it around; thereby returning a number of forward gears and a single reverse. Is the Porsche bolt pattern between engine and bell housing symmetrical thereby allowing the same thing to be done?? Or, could it be done with an adapter?? Honestly, I don't know. BUT, there is another issue introduced with this technique: engine location. Flipping the transaxle effectively lowers the crankshaft of the engine. With a V8 this can be dealt with in a fairly straight forward manner by moving the mounts and installing a thinner profile oil pan. With a flat, boxter engine it is not quite so easy because the entire width of the engine must be accommodated at this new, lower position. (For more on this subject, one might want to read up on what the Porsche powered Daytona Prototypes had to go through in order to utilize the spec tranaxles allowed by Grand Am racing.)

Which technique Graham and/or Fran use is a very legitimate question. I am guessing that the ring gear is flipped. This would appear to be the simplest and least punative course to take. Here the flat boxter engine does not have as severe a penalty of a raised center of gravity that one would experience with a V8 connected to a transaxle in which the input shaft lies above the output (pinion) shaft. (This is one of the disadvantages, in my mind, of the Audi transaxle vs a Porsche transaxle in a GT40: higher station for the V8 crankshaft. Admittedly, this is offset in the opinion of many others by the straight forward bolt up of the two components since the Audi is pointing the right way as designed.)

So, Graham or Fran, which technique does the chassis accommodate?

Regards,
Lynn

[Chuck]

I'd guess (after a year plus absence from the fun auto world - been E55'ing overseas) that they are going to use a 915 series porsche trans and recc the use of the factory or better cooler with a lsd. Flipping the ring gear is easy in these boxes and they bolt up to all the easy access 911 motors.

My choice of power plants would be a 3.8 liter, non-hydraulic rocker 993 based motor a la 993 RS. Twin plug ignition with the 964/993 2x6 cylinder distributor or a real 12 plug italian unit. Carburation has to be the 46 mm PMO's which are so much easier than the webers to keep in tune or my sitting on the shelf big bore mechanical injection from an early 911.

325 hp should be easy to acheive and fairly reliable given the chassis weight.
It'll be interesting to see how a 911 motor responds to such a long exhaust as these will have. Might provide some needed torque which these motors typically want for.

Got to go get the ERA running after sitting for a year. This weekend have to pull the fuel tanks and clean and regasket. woohoo.

Chuck

[91740Gt]

Many apologies Fred for missing your question and thanks to Lynn and Chuck for restarting the thread.

Obviously there are many routes that can be followed with time and money but logically the existing Porsche gearbox route is the one to follow.

Which one ???

In my opinion, there is only one way to go for simplicity, adaptability and weight and that is the 915 box. Just flip the ring gear and away you go.
I,ve had no problems with my set up in a racing format ( LSD, Race gearing, etc ) although the gear change has proved awkward over such a long run from cockpit to the tail of gearbox as the change mechanism is quite notchy.

For me though, weight is all important as well as keeping the whole engine/transmission low, so although other box configurations could be used
I doubt that overall the 915 can be bettered. Please note that i cannot run turbo, supercharging, etc, in the race series that i run in, so stronger boxes are no advantage for me. As for what future customers may want to do .........
who knows ?

The chassis will accomodate pretty well ANY box you want to play with ................ but keep it light.

Graham @ GTA.

[Lynn]

Graham, if you haven't seen any of my posts on WEVO, do a search. They make some really NICE stuff for racing 915s. In particular a sweet side shift mechanism! Edit: Well, maybe "side shift" is not the right term, since the linkage connects back by the (used to be) nose, but they turn the corner and translate the motion in a very slick mechanism.

Chuck, welcome back! I wondered what had happened to my Porsche goto guy, LOL! Actually, I kind of sank into the shadows for a while there myself.


Regards,
Lynn

[Fran Hall RCR]

The RCR917 will use a 930 box with a flipped ring gear.

Original 917 use a 4 speed and we are too.

All Porsche parts and 700hp capability.....

This is the only box that I am authorising for use in the RCR917

[Lynn]

The 93x is a tank, no doubt, Fran!

Regards,
Lynn

[Russ Noble]

I'm a great fan of the 930 trans. Does anyone know what the failure mode is on these things when kitted out with spraybar and billet side plate. The input shaft looks pretty spindly? Will it handle full on raciing starts with 14" race tyres?

Cheers

[Russ Noble]

Sorry for drifting your thread Graham.

Have reposted here http://www.gt40s.com/forum/tech-powe...tml#post173078
Cheers

[John]

With all this talk about putting another engine in other then a Porsche engine, it makes me wonder if it’s possible to cool them. All these engines people are suggesting are liquid cooled, but the body of the 917 was designed for an air cooled engine. Is there room for a radiator in the 917? Will it get air flow?
I don’t have anything against Porsche engines, but I just don’t think an air cooled 6 is going to do justice as replacement for the original 12-cyl; especially if your trying to hit the originals HP numbers, around 580hp if I’m not mistaken. I also wonder how 6-cyl torque feels on a 4 speed trans…

[91740Gt]

John,

There is no question that a water cooled engine could be fitted, ducted air and fans, etc. It is down to the individual what he or she wants to do.

A 6 cylinder twin turbo engine will easily give you the hp if you want to splash out.

BUT, and i,m sorry to say this by starting with a "but", these 917s are being built as rolling chassis as per the originals. What you fit, rightly or wrongly, is down to you.

917s ran both four and five speed boxes and i can tell you that with such a lightweight chassis both my existing car and the new RCRs do not and will not have any torque issues.

Place your order with Fran, and then go out and buy an original engine and gearbox and all the associated injection and electrics and backup spares for it. The probability is that you will be at least £200,000 pounds lighter in pocket before you get the car !!!!!

I race my 917 and the regulations do not allow super or turbo charging in the UK based race series.

I say it once more.... Its all down to the individual and what they want to do with their 917.

GT.

[91740Gt]

If anyone interested i found a couple more shots that are downloadable to this subject. I,ve loads more but they are all too large to send and i don,t know how to resize.

Anyway the head-on shot was taken at Spa by someone at, i assume, la source hairpin ??

Regards,

Graham.

[91740Gt]

Just looking at these pictures just goes to show how very different the Powder Blue and Marigold Gulf livery can look in different light and with different photographers and filters.

I know that many moons ago i tried to explain the variations in different light and how impossible it is to get the "correct" colour !!!!!

Graham.

[Malcolm]

Hi Graham, long time no chat! Hope all is well in your garage! Totally agree with you on different lighting changing colours. I use metal halide ligfhts in my garage and as they warm up the colours of my cars go beserk. My red tractor becomes purple and the blue on the 40 goes white! The top picture makes the blue look similar to my 40's blue whereas the lower picture is more as I remember your car. Did I spot your car used in an advert by Leda Suspension?

[91740Gt]

Malcolm,

Yes, you are correct. Leda built special shock absorbers for me and supply me with ever changing spring rates at no cost !! Beverley and John have always been fantastic, thus saving me a small fortune, and i in turn always promote them by carrying their logos on the cars and tow van and recommending them to other customers.

Regards,

Graham.

[RichB]

What's the maximum height of driver that can be comfortably (safely!) accomodated in a 917 (real or replica) ?