383 Driver Car Build Suggestions

Engine, Trans & Driveline

  1. hsorman

    hsorman FBBO Gold Member FBBO Gold Member

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    While I am waiting for title issues on my 1970 Road Runner :angryfire:, I have been thinking about the engine/drive-line build.

    My starting point is a stock, 80,000 mile 335 HP 383 with a 4 speed and 3.55 8 3/4.

    Goals: 400+ Horsepower and 20 MPG highway, keep the original 383, A-833 and keep the air grabber functional. Run on premium gas (92-93 octane). I would like to make the car a really nice reliable driver car with a broad, flat torque profile. Do this without sacrificing the true Road Runner "spirit" - car still needs to leave a traffic light like the muscle car it is!

    Some starting thoughts:
    Engine: Leave as 383 CI, short block fairly stock, except perhaps a higher lift/duration cam (specs?). Add aftermarket aluminum heads (which?), dual plane manifold, headers and fuel injection. Add 2.5" exhaust with X pipe.
    Transmission & Rear: Stock except add a Gear Vendors overdrive.

    Having said the above, I am no expert, and don't know ideal specs on anything to achieve the stated goals.

    I'd like to hear comments and suggestions from the gurus on the forum!

    Thanks in advance!

    Hawk
     
  2. 1948 santa

    1948 santa Well-Known Member

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    In the day (1970) if we got 10 MPG that was good and that was with a low milage engine.
     
    Last edited: Dec 26, 2012
  3. RustyRatRod

    RustyRatRod Well-Known Member

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    Unless you're willing to give on the 20 MPG, forget it.
     
  4. BeastlyBirdie

    BeastlyBirdie Well-Known Member

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    Gear vendors is a lot of extra money, check passon and their overdrive. If I am thinking right gear vendors is a splitter, isn't it? Anyway, really working the valve job, head flow, not just bigger, more efficient, and on and on, might get 14 out of it. But remember, you are pushing a brick down the road. There's a point where you will spend more money getting half an mpg then you will save with the extra half mpg.
     
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    • Cranky

      Cranky Banned Staff Member FBBO Gold Member

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      Had a 70 383 Challenger with a dual point mechanical distributor, AVS carb that was tuned well, timing advanced and it got 12. Replaced the 3.23's with a 2.76 and it went to 16. Not going to say you can't do that but it will take some study and that road runner is not as slick as the Challenger.
       
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      • hsorman

        hsorman FBBO Gold Member FBBO Gold Member

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        Thanks for the replies.

        I agree that aerodynamics are going to make highway mileage suffer (maybe I should get a superbird :grin:).

        The 20 MPG highway is not a requirement. I guess my goals are to make as efficient an engine as possible. A new HEMI, for example, gets 25 highway. I don't want a new HEMI, but want to take advantage of new technology that has been developed since 1970.

        It seems that there have been a lot of improvements in head design and camshaft profiles. Cams seem to be open longer and with greater lift. Likewise, new heads seem to flow really well. I guess both help the airflow of the engine. If you couple that with much more fuel efficient fuel injection, and an overdrive, I certainly would hope that I could improve dramatically on 1970...
         
      • 67steve

        67steve Well-Known Member

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        you will need to go with a fuel injection to get any improvements in mpg, there are many availabe, this will also provide an overall tuning advantage to a carb any day. also compare the price difference between 92 and 87.
        e
         
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        • Blue Demon

          Blue Demon New Member

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          • BeastlyBirdie

            BeastlyBirdie Well-Known Member

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            As for cam design, the only real change has been roller. Cams aren't "open longer with greater lift." They do have different ramp profiles, but lift and duration for hydraulic cams are still similar to 40 years ago. Isky and erson had some radical runs, let alone the old mopar 509. Lift and duration-bigger means less mpg.
             
          • 68383GTS

            68383GTS Well-Known Member

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            20 MPG thats funny.You better put a 318 in it.
             
          • fatecaptured

            fatecaptured Well-Known Member

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            I was thinking new hemi myself.
             
          • 67 coronet

            67 coronet Well-Known Member

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            the 20+ mpg you see out of the new hemi's is mostly due to the spark control technology.they basically turn into 4 cyl eng's at freeway speed's.most people that do the change over convert to a simpler comp and loose that super millage #.i think 16 mpg is obtainable with a good breathing eng and fuel injection.you may sacrifice some power,but still have more then enough for the street.find a fuel injection that is tuneable from inside the car and you can get the best of both worlds.
             
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            • hsorman

              hsorman FBBO Gold Member FBBO Gold Member

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              Without trying to push the limits, we would still be happy with 335HP out of a 383. Now we have mid 400s horsepower out of 300 cubic inch motors that are normally aspirated.

              I realize these modern day cars use a lot of computer technology to achieve this, but the trickle down affect means that some of this should be (and is) available to us hot rodders. The purpose of my post is simply to explore those options. A 318 'aint one of them...
               
            • lewtot184

              lewtot184 Well-Known Member

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              something to keep in mind is that the chrysler b engine is a product of 1950's technology. you'd have to throw an awful lot of money at it to reach modern standards. a 400hp 383 won't make any torque below 3000rpm and you'll need to cruise at 2000rpm or less for 20mpg; don't think it'll ever happen.
               
            • IQ52

              IQ52 Well-Known Member

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              I haven't run a 383 in a passenger car for a long time. But, in the late 1970's early 1980's, I ran a 383 with a 6-pack in a '69 4-speed Road Runner with 3.55 gears and it got 16-17 mpg on a regular basis. Put the engine in a 4-speed '73 Challenger with 3.91 gears and the wife would get 19 mpg while I was stuck at 15 mpg. It was so long ago I don't remember exactly how the engine was built, other than it had ported iron heads and a Camonics hydraulic flat tappet camshaft.
               
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              • dangina

                dangina Well-Known Member

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                • RustyRatRod

                  RustyRatRod Well-Known Member

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                  As far as MPG, you're right, but for performance, I can't agree. Lobe design has come light years ahead of even the old Purple Shaft redesign in the 1980s. Of course, along with that new lobe technology, come more violent valve train action and more noise. It's certainly a tradeoff. While the lastes, greatest and fastest rates of lift are cutting edge for sure and they DO work well, 9 out of 10 street cars wil never know the difference between those and some kind of old school grind.

                   
                • BeastlyBirdie

                  BeastlyBirdie Well-Known Member

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                  I was actually meaning for mpg, and trying to help the op understand that his statement was a little off. Its not so much the duration and lift that has changed, but the ramp to achieve the lift. Meaning, .510 lift is still.510, just how the valve gets that open is different on a newer cam designs. I think we're on the same page here. Anyway, higher lift and more duration won't gain mileage.
                   
                • PurpleBeeper

                  PurpleBeeper Well-Known Member

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                  OK, here's my 2-cents.

                  Keep the 383 but put a six pack on it (mileage). Look for a VERY conservative cam (RV cam or maybe even keep a stock cam in it). Keep the stock heads, but do a maximum amount of porting, port matching, etc. The mild cam will also let you get away with 2.76 gears without frying the clutch & go ahead and install some type of overdrive transmission. Again, just my 2-cents.

                  My "guess" would be 300 hp & 16 mpg

                  Oh yeah, use the stock intake manifold to avoid air cleaner to air grabber hood clearance issues
                   
                • RustyRatRod

                  RustyRatRod Well-Known Member

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                  Oh yeah.......I was essentially agreein with you in the MPG thing.


                   
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