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Thread: Spec Class for '64-'65 911s

  1. #11
    Join Date
    Nov 2004
    Scottsdale, AZ
    I don’t see the 39/35 valve size as a problem at all. What’s the port spec?

    190hp out of a 2.0? That would qualify you in the back of the pack in U.S., everything else being equal. Are ti parts free? Compression? Fuel? How about flywheels and clutches?

    As far as 9k with 906 cams... me thinks that’s a fairy tale. 906 cams simply won’t do that.

    We were testing to 9500 several years ago and wearing the valve guides out every 5 hours. Now we cap at 8500. A strong 2.0 easily makes 230+hp. But just as important is getting reciprocating/rotating mass way down.

  2. #12
    I do understand that 906 cams won't achieve 9000rpm and I believe that Port Sizes should be the stock sizes shown on the Homologation Form.

    The 190 BHP engine we used was installed in a Rally Car used on Gravel and was built in around 2003. Apart from cams and pistons it was relatively standard and again I do agree that it wouldn't be competitive.

    Appendix K makes it clear that reproduction parts should use 'period' technology in terms of materials and manufacturing methods and has some emphasis with regard to weight.

    I think that using Ti valves or rods is questionable but tempting.

    Appendix K does make it clear that Pistons and Cams are free and as I said in my earlier post I think that some engines use wrist pin diameters of 19mm and reduced diameter crank pins. I believe that rod weights for this configuration are around 450 grammes.

    Flywheels are generally '906' style and I am not sure about clutches.

    It is relatively easy to buy a competitive engine as there are several companies that will provide the service but understandably there isn't much detail provided.

    We have the basic valve train sorted out and we will use hollow stem valves and 'Trojan' valve guides.

    I am trying to learn more about suitable cam profiles and we are just about to finalise piston specifications.

    We have a crank being manufactured and rods are also a difficult choice.

    All very challenging.

  3. #13
    Quote Originally Posted by Frank Beck View Post
    A strong 2.0 easily makes 230+hp. But just as important is getting reciprocating/rotating mass way down.
    Ok Frank how about some details? Induction, crank, pistons, ignition etc. Is that 230 HP with "Modern" components like EFI/ITB/Motec or with Solexes or 46IDA/PMO?

    I suppose you could have the same size ports but different port shape if you started with Xtreme heads.

    I am running a symposium over on Pelican about "state of the art" and have gotten some interesting initial responses there.
    1966 911 #304065 Irischgruen

  4. #14
    It's rumored a certain Florida shop gets 275ish hp from a 2 ltr.

  5. #15
    Join Date
    Nov 2004
    Scottsdale, AZ

    2.0 “State of the Art” right now is being done primarily in vintage racing (stakes are high enough to justify spending the dough) and EFI isn’t allowed, otherwise 275hp might be a possibility.

    As far as divulging “secrets” I can tell you we save an honest 30 lbs of reciprocating/rotating weight over stock, dinosaur Porsche components.

    This is my bread and butter so I have no reason to spill too much. I will say I’m a big fan of Pauter rockers (they break... when they’re supposed to break) and will recommend Brian’s billet heads over Xtreme in a NY minute.

  6. #16
    <iframe width="560" height="315" src="" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

    This is from 2016
    1966 911 #304065 Irischgruen

  7. #17
    Senior Member
    Join Date
    Nov 2003
    Santa Monica CA
    I know these are 1965 cars with 901/01 engines. would a racer be disqualified if he had a 901/5 ,901/6 or 901/7 aluminum engine in his 65 911?
    1. Chris-Early S Registry#205
    2. '70 911S Tangerine
    3. '68 911L Euro Ossi Blue

  8. #18
    Appendix K suggests that it is the 'specification' that is important and not the year of manufacture and as such I would imagine that it is possible to use any of the early 'sand cast' engine cases and obtain valid FIA paperwork.

    The engine Type Number isn't specified on the Homologation Form, the casting numbers aren't stated and the only real description of the Casing is the material which is described as 'Leichtmetall' and was usually meant to describe Aluminium as opposed to Cast Iron.

    I do believe that it would be possible to obtain an HTP using any of the early casings but this is where it starts to become tricky.

    The Peter Auto 2.0L Cup regulations clearly state then engine cases must be 901 or 901/01. It also states cars must have an HTP. It is not clear which of these statements is definitive so to be 'safe' I feel that a 901/01 type casing is needed for this series.

    The 2.0L Cup regulations also state that all cars must use a rear caliper with a 35mm diameter piston despite the simple fact that Homologation Form 183 clearly allows the use of a caliper with a 38mm diameter piston.

    I also believe that many of the engines being used have Nikasil Cylinders which I don't think strictly comply.

    All of the contacts listed in the Peter Auto documentation are Companies involved in the preparation of cars used in this Series and the FIA Scrutineers that inspect the cars to provide an HTP will not comment about these additional requirements.

    I do agree that 275BHP is the benchmark for these engines - the question is how to get there.
    Last edited by chris_seven; 06-12-2018 at 01:25 AM.

  9. #19
    Senior Member RennTyp's Avatar
    Join Date
    Apr 2006
    Oxford, UK

    FIA Period F Engine Specs

    In European historic racing at the moment there is the theoretical spec you need to comply with (i.e. the homologation forms) and then there is the actual spec that different race organisers will permit without complaint. Disappointingly this latter category can deviate significantly from the first depending on the event, the organiser, who you are and the amount of money you spend with said organiser. There are some truly blatant cheats going on in many cases with the full knowledge of the race organiser. I know this from having spoken to scrutineers who have been directed to accept cars that don't comply. I myself bought an "FIA spec" car that had run in some of the biggest events in Europe and when we took the engine apart it was 3.0L not 2.0L!! Mind you that would explain the 915 gearbox it was also running! From what I understand it's the 2.0L Cup's ambition to strictly enforce the homologation specs and this will be a definite step in the right direction. It might create a bit of an arms race but it will be very interesting to see what the various tuners can do with a 65 engine.
    Early 911S Registry #888

  10. #20
    Ach-toong!. . . 3,0 liters and a 915 box!

    Heard in the race paddock:

    "Those guys are cheating."

    "How do you know?"

    "Because I'm cheating, and they are faster than me."

    * * *

    I have been browsing the old videos of the Goodwood members meetings. . . the Chris Harris ones are great, he seems (on camera, never met him) to be a solid guy.

    Anyway check this one out at 1:00 in-- that is a Bosch BLUE coil my friends, no way is that going to support full spark energy at 7000 rpm, even if you were using a Pertronix or Hot-spark electronic ignition. The primary resistance and inductance are simply too high to allow charging between ignition events.

    The Bosch points can handle about four amps before they melt particularly at high RPM. Solid-state drivers can pass at least seven amps, allowing you to charge the coil fully between ignition events. But you would use a low primary resistance coil in that case.

    Anyway it looks like the Appendix K rules say you must use a coil with a minimum of three ohms.

    Cars of Period F with evidence of period use of electronic ignition may use a non-period electronic ignition system provided this system is triggered by contact breaker(s), utilises an ignition coil with a minimum resistance of 3 ohms, the spark is distributed by a rotor arm and the timing of the spark is controlled entirely by mechanical means.
    The Delta Mark Ten is out, made too late.

    I think the best solution would be an original coil with 2,1 ohms primary resistance and the 0,9 ohm ballast resistor. That would easily satisfy the rules and get you the minimum resistance possible for max spark energy while at the same time not burning the points.
    1966 911 #304065 Irischgruen

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