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Thread: Hot 2 liter engines

  1. #21
    Quote Originally Posted by raspy2point2 View Post
    why was the small valve rule changed?
    The cars are all 1965's and they wanted them to be period valve sizes, maybe it's an appendix K thing? They outlawed the Duel motorsport exhaust for last year too (which I also now have in stock) ) The funny thing is, don't think for one minute they make less power than the big valve engines. That's race engineering for you.

  2. #22
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    '69 was the last year before stronger NOx protections in the USA made the 10-1 compression ratio that helped the little ’69S motors to be the highest power-to-displacement of any showroom available 911 far too dirty to pass DMV inspection.

    That's why there was no 1968 911S. Porsche couldn’t pass EPA with the old-school 1968 setup.
    So they made the "L" (LuX) to try and capture the upscale profits of a "S" model.
    The 1969's 10-1 compression ratio was reduced but the "L" included all the pricy “S” options except speed.

    Porsche went to work to meet the EPA standards and I bet it cost them a fortune...

    The 2.0 1969S valve port sizes, sodium filled exhaust valves, 10-1 compression ratio, 69S cam profiles, brand new Bosch high energy ignition and of course 1st year Mechanical Fuel Injection all come together to make the little (stock) '69 2 liter S motor so special, relatively CLEAN yet POWERFUL.

    All that with a lightweight Mg engine and transaxle case.

    It was 20 or more HP up from the 2.0 '67S...

    1492 were made. How many are left????

    Not until heavy electronic engine management and vario-cam did anything come close to 97 SAE HP / liter of the little two-liter N/A 69S Giant Killer in a showroom available 911.




    So did EPA scientists inadvertently create one of the very best little asphalt burners so-far?????



    Drive one and see...

  3. #23
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    67 911S -160 hp; 69 911S- 170 hp; 1970 911S-180 hp 1972 911S-190 hp. they all only went up by 10 horses at a time
    1. Chris-Early S Registry#205
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  4. #24
    Senior Member beh911's Avatar
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    Quote Originally Posted by raspy2point2 View Post
    67 911S -160 hp; 69 911S- 170 hp; 1970 911S-180 hp 1972 911S-190 hp. they all only went up by 10 horses at a time
    Just to clarify, these are the DIN hp ratings.
    SAE ratings are higher and confusingly match power ratings of other years, making people debate this topic.
    1969 S Coupe #761
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  5. #25
    Senior Member Fubawu's Avatar
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    Quote Originally Posted by Schläfer View Post
    The cars are all 1965's and they wanted them to be period valve sizes, maybe it's an appendix K thing? They outlawed the Duel motorsport exhaust for last year too (which I also now have in stock) ) The funny thing is, don't think for one minute they make less power than the big valve engines. That's race engineering for you.
    With stock valves now, is it all done with porting?
    What compression are you able to achieve?
    Cams?

    I also read that the only eligible exhaust manifold is Dansk?
    Last edited by Fubawu; 02-11-2020 at 09:57 AM.
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  6. #26
    Why was the Duel exhaust outlawed???? I thought the exhaust from the port outwards was free.
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  7. #27
    Quote Originally Posted by edmayo View Post
    Why was the Duel exhaust outlawed???? I thought the exhaust from the port outwards was free.
    I believe the headers now have to be of the original design. A new exhaust was developed between one of the front runners and EB motorsport, but I believe there have been some complaints and I'm not sure they'll be allowed to run that system either for the up and coming season.

    The compression ratios are 'getting up there', but I can't say more than that. Understandably each of the builders have their own speed secrets.

  8. #28
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    Manifolds are regulated, silencers are free. That's not series-specific, it's pure Appendix K and applied in-period. The rules aren't being changed in historic racing so much as being enforced - sometimes for the first time!

  9. #29
    As others have mentioned before, lots of differences. Here are the main ones:

    - Carrera 6 had a different case from 2.0 911S
    - Solid valve gear (the rockers didn't have the adjusting nut at the end) which used shimmed tappets to adjust for valve clearance. With solid rockers engine was good to 8000RPM (incidentally, Porsche used the same solid rockers on all their race engines, all the way up to the 962)
    - Larger valves, larger ports
    - Different pistons and barrels (CR over 10)
    - Center lubed cams and different cam profile (more top end horsepower)
    - Twin plug ignition
    - Taller intake manifolds
    - 46 instead of 40 Weber carburetors

    Later on C6 engine used fuel injection which was good for another 10 hp or so.

    To my mind the biggest difference is the solid valve gear, without it all naturally aspirated aircooled 911 engines are done at 7300 RPM.
    As with any naturally aspirated engine, revs are your friend!

    In terms of being tractable, I think most people exaggerate how peaky the S or R or C6 engines were. Having driven all of them (on track and on street) they're just great fun. Yes, you shift a bit more (compared to a torque engine) but so what, to me that's what makes it interesting.

    My 68T Sports Purpose is a blast to drive on the street. It's a 2L alu case with S pistons & barrels, S valves, T ports (which lowers the torque curve), T crank (spins up quicker), 40 Webers with large 34 mm venturis (jetted accordingly), 68S ignition (Bosch distributor with points etc.), free-flow intake and open rallye exhaust. It's perfectly fine in traffic and once you get to 5K RPM it wants to go again and pulls to 7300.

    If you want to ruin your street car, just put a lightweight flywheel in it - but revs never hurt anyone

    Ciao,
    n.
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  10. #30
    Quote Originally Posted by TargaFlorio View Post
    To my mind the biggest difference is the solid valve gear, without it all naturally aspirated aircooled 911 engines are done at 7300 RPM.
    I can't fully agree with that, the 2 litre cup cars all rev to 8k, they're not using solid rockers.

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