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Thread: 2.4S to modify or not to modify?

  1. #1

    2.4S to modify or not to modify?

    I'm new to this board, so excuse me if this is a basic question.

    I'm just purchasing my first early 911, a 73'S with matching 2.4L S engine. Its stock, but needs a rebuild.

    There are two modifications I've heard a lot about that seems to improve the driveability and maintence of these engines.

    1- 'Modified S cams' - guess these are new CAD designed CAMs that improve the power band. Anyone had experience withthese and can you recommend where to get them from?

    2 - Twin Plug - I'm told you re-machine the original heads with a second hole for the second plug vs new heads? What about alternators?

    Any general comments, opinions, referrals, etc.. are welcome. Also, anyone know how much this adds in power?

    Thanks,

    Chris

  2. #2
    Having your heads drilled out for the second plug is the easy/cheap part. Getting something to fire that second plug is a different story. I think the most cost efficent thing to do is a whole engine swap with a 3.6 as the motor and flywheel/clutch parts are going to set you back less than a correct rebuild of your 2.4 S motor.

    Ask racea911 how much it costs to do a rebuild the right way. Add to that the cost of modifying your heads, porting, raising the CR, and modifying your MFI to take advantage of all this. Unless you are sitting on a secret stash of NOS dual point distributors I guessing you are either going to have to switch your gear on the crank to a later backwards design and use a 964/993 distributor, or run a crank fire system.

    Sorry I can't paint a nicer picture.
    Torsion Bar Impaired... again.

  3. #3
    Moderator Chuck Miller's Avatar
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    Chris,

    As an owner of a stock motored 2.4-S for the 14 years I would suggest that you rebuild yours to stock factory specs. If I had a 'fresh' stock engine I would go faster then I go now… and that ain't to slow… just ask ;-) My 2.4-S was good enough for the H-Improved record for the POC Short Track Series, 7 first in class trophies, and the embarrassment of a lot of bigger displacement cars.

    On the other hand… at 164,000 miles, AND a 4th to 3rd miss shift at about 120mph at Willow Springs, I'm getting ready to pull the trigger on the BIG REBUILD… AND I'm considering converting my 2.4-S to 2.7RS …

    And so it goes...
    Chuck Miller
    Creative Advisor/Message Board Moderator - Early 911S Registry #109
    R Gruppe #88

    TYP901 #62
    '73S cpe #1099 - Matched # 2.7/9.5 RS spec rebuild
    '67 Malibu 327 spt cpe - Period 350 Rebuild

    ’98 Chevy S-10 – Utility
    ’15 GTI – Commuter

  4. #4
    Originally posted by Chuck Miller
    My 2.4-S was good enough for the H-Improved record for the POC Short Track Series, 7 first in class trophies, and the embarrassment of a lot of bigger displacement cars.

    On the other hand… at 164,000 miles, AND a 4th to 3rd miss shift at about 120mph at Willow Springs, I'm getting ready to pull the trigger on the BIG REBUILD… AND I'm considering converting my 2.4-S to 2.7RS …
    Chuck,
    Why don't you try 2.2S pistons? From '73 onwards, there are two types of 7R crankcases - 2.4 and 2.7, so if you want to convert to 2.7 you would have to buy a 2.7 version case. Enlarging 2.4 case is not exactly good practice, is it? So, I think it's better you get your old case shuffle-pinned and use 2.2S pistons.
    RS engine is prone to head stud failure and thermal expansion, anyway.

  5. #5

    Beg to differ

    Here's my two cents worth. I built my 73S motor to 2.7 RS spec.
    19 years and 142,000 miles ago and it still runs VERY GOOD! I don't have too much trouble staying up with the 3.6 guys out on the open road. On the track it still does pretty good even though it is not set up for the track.
    Starting with a 2.4 S is a great place to start you just need piston & cylinders 2.7 2.8 or 2.9, recaibrate the MFI pump, ignition distributor and all the standard things for a normal overhaul. If you really want to go twin plug, have the heads tapped when they're at the machine shop for valves and guides.
    You have to decide what you want to achieve, pencil it out, a staight in and out overhaul or all the mods needed to change over to late motor.
    In my opinion, bigger is not necessarly better. No matter how big you go, someone will always be faster! I like period correct looking engines.

    All the best!

    Roger Grago
    R Gruppe #27
    73 RS-T
    70 2.4MFI VW Bus

    BTW I'm trying to convince Chuck Miller to build his to RS spec. even though his 2.4S was impossiable for ME to out run. How stupid am I!

  6. #6
    Slow In...fast Out RSupdate's Avatar
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    Originally posted by Chuck Miller
    ......… AND I'm considering converting my 2.4-S to 2.7RS …
    Chuck !!!! Say it ain't so !!!!
    Johnny Riz
    73E euro 3.2 w. a few goodies
    Rgrp 152
    S Reg 335

  7. #7
    My opinion would be if you're restoring an early S, then keep it stock. If you want a modified car, then I would think it would make more sense to start with a T, or a 74-89 tub.

    Then again, it's going to be your name on the title, so take my opinion for what it cost you.

  8. #8
    Most of the comments seem to be around going faster. While that's always nice, I learned a while ago that someone else is always faster (happened one evening driving home in my 1997 993 when a guy in an early 911S wanted to drag race me on the freeway - he kicked my ass from about 55mph up to 90, then I took him up to 120 or so).

    That said, my modifications were more for driveability and maintenance. I've been told the S engine is not so great on low end torque so you need to drive it with high revs. Most of my driving will be around town (no freeway work commute). Also, I read that these engines foul plugs a lot, especially when not driven hard. The guy doing the engine has told me that its about another $3K to make these mods, which would still keep the engine 'mostly stock'. I'm trying to figure out if its worth it. I'd hate to spend the money on the rebuild, have everything put back in, than decide I want it pulled out and redone again.

  9. #9
    Originally posted by yopurp
    I've been told the S engine is not so great on low end torque so you need to drive it with high revs.
    2.2S pistons will improve the low end torque, I believe. Anyone can confirm?

  10. #10
    Senior Member curtisaa's Avatar
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    Re: Beg to differ

    [QUOTE]Originally posted by rst73
    [B]Here's my two cents worth. I built my 73S motor to 2.7 RS spec.
    19 years and 142,000 miles ago and it still runs VERY GOOD! I don't have too much trouble staying up with the 3.6 guys out on the open road. On the track it still does pretty good even though it is not set up for the track.

    I would have to go along with Mr.Grago on this one. He has always seemed to hang with the 3.6 guys on the open road. I would also concur with the 2.7RS motor spec advice. If I had the $$ to buy an S, I would certainly would not be deterred if the "owiginal" case was made to 2.5, 2.7,2.8, or even like Daves' RS...2.9...

    After all...didn't the factory do that when it created the 73RS ??

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