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The engine for the hot rod came with some old paperwork.
Here is the invoice from ANDIAL Road and Racing for the used Porsche 2,5L Race Motor, disassembly, balance, reassembly and dynotime back in 1982.
The document headed EXHIBIT "A" provides a list of key component parts.
Another interesting old document is the ANDIAL RACING dyno sheet for Andial Nr. 129.
Engine Type 2.5L
Case Nr. 2502
Andial Nr. 129
Bore 86.7
Stroke 70.4
Volume 2491ccm
Compr. Ratio 10.5/1
Timing 28*
Pump 1077
Date Feb 15/82
It shows peak PS corrected of 279.0 at RPM of 7962, using a correction factor of 1.04.
Timing: 28* at 7500 RPM
Valve Clearance: .15mm Intake & Ex.
Pump timing: 14* BTDC #4 Firing
Cam timing: 6.2mm
A long stroke 2,5L engine in the ST era would have been fitted with a Marelli twin spark distributor and two three pin Bosch CDI boxes.
Andial 129 was fitted with the later Bosch breakerless distributor and two eight pin Bosch CDI boxes of a 3,0 RSR.
Andial had eight pin boxes for their dyno, but had none to sell. When the buyer of the engine called Bosch USA to order the eight pin CDI boxes, the part numbers did not yet exist in their catalog!
Here is a scan of a wiring diagram that Andial sent for an ignition system employing eight pin CDI boxes.
The original owner of the engine found that his tacho did not work with the Bosch breakerless/twin 8 pin CDI set up.
Andial supplied him with a "Tach 10,000 RPM (used)" to work with the ignition set up.
The tach and 8 pin boxes came with the engine.
Here is a scan of the invoice from ANDIAL ROAD and RACING for the tach.
We will use the same old used 10k tacho from ANDIAL in the hot rod.
An indispensable guide to general information and parts numbers for all things ST is the Porsche Spare Parts List TYPE 911 S competition type
Here is the fly page from an old april 70 edition.
It has the name J Truman handwritten in ink on the front page.
This has been a big help in figuring out which parts to use for the hot rod.
Has anyone every reproduced that document? I'd give my eye-teeth for a look-see.
Stu
For the sake of comparison, here are the factory specs of a TYP 911/70 long stroke 2,5 engine.
Bore 86.7 mm
Stroke 70.4mm
Displacement 2492cc
Mechanical Fuel Injection
10.3:1 Compression Ratio
Heads twin plug
Distributor Marelli twin spark
Cam Timing: as per TYP 906
Peak Power 270 PS @ 8000 RPM
Peak Torque 191.6 Foot-pounds @ 5300 RPM
The Andial dyno sheet indicates that their engine nbr. 129, also a long stroke 2,5 made peak power of 279 PS @ 7962 RPM, a very slight increase relative to TYP 911/70, especially given the use of a correction factor. Two variations on the specs of 129 may have accounted for the small power increase, cam timing/lift and compression.
The cams were specially ground by Porsche for the engine according to "Exhibit A" posted earlier. Perhaps these cams share the higher lift characteristics of the RSR Sprint developed by Kremer for the RSR and used by most racers in place the old 906 spec mfi cams.
The cams from ANDIAL 129 have been sent out to put on the Cam Doctor so the exact specs can be determined.
Another factor contributing to the slight power increase over the factory specs is a compression bump from the standard 10.3 to 10.5.
Here is the only known picture taken in the factory of a 2,5L race engine.
This photo was taken by Mike Keyser of Toad Hall Racing during a visit to the Race Department and the photo appears in his book The Speed Merchants. Scan courtesy of Jim Calzia from a old post in another thread. Cameras were generally verboten in the Race Department so I wonder if Keyser took this grainy exposure on a palmed Minox camera?
It is a very interesting photo. I guess something really special is under that drop cloth in the backgroud.
The engine mount bar, which is heavy, is the standard (non-light weight) piece while the exhaust carrier on this 2,5, if like the RSR piece, is ridiculously light, but has been lightened still further. They got this figured out for the 2,8 RSR which had a drilled engine mount bar and an undrilled exhaust carrier - makes more sense that way.
Marelli 30mm neck distributor, amber tin, period correct metal fuel injection lines (toussled head lines not yet in use 'til 935?) race pump with support bracket and of course high butterfly with small inlet funnels are all in evidence. These inlet funnels appear to be painted black, which I am told is correct. All 2,5 inlet funnels are made in steel as far as I know.
Tom:
Thanks for posting the details of the engine and ignition system. What are the sizes of the ports and bottom of the HB stacks? The wiring diagram for the 8 pin CD boxes is interesting, as it is the same as for the 6 pin Bosch CD I am using on my 2.5L, except pins 4 & 6 are connected between the 2 boxes. I guess this is to make sure the sparks occur at the same time.
Do you know what cam grind Andial used...was it the RSR Sprint?
You will have a very special engine from the looks of all the Andial documentation and the original equipment on the engine. I have always wondered how the MFI pump brace was attached...it appears there must be threaded bosses in the case for it? Do you know why the ST and RSR engines used this brace? Seems the standard pump is pretty stable with 4 mounting bolts to the case and only a cogged belt to pull on it.
Keep the details coming...very interesting stuff!
Gib
Edit: Was composing this as you were giving some of the cam details in another post....thanks.
Wow Tom!
that is soo cool to have all those receipts and thank you so much for sharing them; my neck is now permanently angled 90 degrees :D
BTW- i noticed the nology hot wire spark plug cables- definitely not 1983 issue! These work quite well on a capacitor principle. We dyno tested these wires years ago, and despite the poor plug connectors, they yielded a real 5 hp
Mike- we have the castings already in hand for the hand grenade filter. We made 20 pieces and 12 are already spoken for. Currently we have a real one and new casting at the machinist for evaluation on what it will cost / time to get it ready for installation. Our plan is to offer it in two configurations a) as original with by pass valves b) or as full flow, so you keep the oe thermostat in place on the block. For filters we are considering a single piece pleated stainless mesh screen insert, as the "leaf" filters were not the best when it came to being sealed on the inner circumference of the housing. Note that we had all the part numbers, casting "warts" exactly like the donor housing that was used. As we are using aluminum instead of mag, we will anodize it black. When it comes out of the bath, it looks amazingly like magnesium. I don't have any pricing yet, but they will be fairly priced and once this set of 20 are gone, it may be another year before we make more.
Roll bar bases- yes , we will inform everyone on this board once we have an idea on price and timing
Stu- i have a photo copy of the sports purpose booklet. Will make you one
Sorry to hijack this part of the thread, but i wanted to let everyone know what we are doing
thanks!
Dave
Hi Gib:
1. What are the sizes of the ports and bottom of the HB stacks?
A. The diameter of the intake port on the heads is 41mm. The diameter of the bottom of the stack is 41mm. As a matter of interest, the exhaust port on the heads is also 41mm.
2. Do you know what cam grind Andial used...was it the RSR Sprint?
A. I don't know, yet. We sent the cams out to be put on a Cam Doctor as the exact specs are not shown on the Andial documents. As they came from Porsche in a used engine, Andial probably did not know the exact grind. I speculate that they may be RSR Sprint or some other higher lift versions of the 906 mfi cam. We will know shortly from the results from Cam Doctor. There are better grinds around, I am sure, but I would like to use the old stuff if it is serviceable.
The standard cam for 2.5 race engines was the mfi version of the 906. Here are the 906 specs with the factory RSR cams (the RSR specs are are for the Werks cam, not the Sprint version developed by Erwin Kremer with Dr. Schrick) shown for comparison.
906 Lift I/E: 11.73/10.24; Duration I/E (deg crank) 281/251; Lobe Center (deg camshaft) 95; Intake Valve Overlap 6.7*-6.9*
RSR Lift I/E: 11.79/11.43; Duration I/E (deg crank) 278/267; Lobe Center (deg camshaft) 101; Intake Valve Overlap 6.1*-6.3*
As a side note, the RSR Sprint was developed by Erwin Kremer in conjunction with Dr. Schrick. The RSR Sprint was remembered by Kremer in his interview with John Starkey in The Racing Porsches R to RSR as follows: "The valve lift was higher and we made 20 pairs. The maximum power we obtained before we used these was 323 bhp. With the Schrick camshafts it was 345-348 bhp. The engine did not last so long, only maybe two short races, certainly not 1,000 kilometre events. The works camshafts were for the long distance races." These bhp figures are for the 3,0 RSR engine with slide throttles.
The modern grinds generally use bigger lobe centers, more lift and less duration continuing that trend from the direction established by the RSR grind as compared to the 906 cams.
3. Do you know why the ST and RSR engines used this brace?
A. This is pure speculation on my part but I assume that it is to keep the pump from torquing when put under sudden accelerative loads. Perhaps the engineers were concerned about "working" the metal high pressure fuel injection lines by attempting to insulate the pump from outside forces. I think this makes sense because a couple of years later the Race Dept switched to the highly flexible "toussled head" fuel lines (as seen on nbr 129) on all the race engines, further addressing the issue.
Essentially, the support brace functions as a turn buckle to stabilize the pump and is rubber bushed on both ends to reduce vibration. Perhaps this also aided in maintaining the pump settings and alignment of the pump linkage when put under severe use.
It looks to have been made up from standard bits listed in a German catalog of industrial hardware.
Maybe Aaron or Steve or Matt Blast can give us a more knowledgeable answer.
Thanks for sharing the info about the wiring for the six pin CDIs.
I will post specs of the ANDIAL 129 cams once known.