71 383 - options

Big Block A body Tech

  1. matthon

    matthon Well-Known Member

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    71 383 HP with a stock 4 barrel intake, complete except no carb, 346 heads. Assumed 8.5:1 compression.
    Pulled valve covers and exhaust manifolds, looks clean, been sitting inside a friend's heated garage for years.

    Going in car with headers, dual exhaust, and a 4 speed, crank has correct hole/bearing.

    I have extra parts from another 383, including a Performer RPM intake and Holley 750, (also a tunnel ram and matching 600s).

    Small budget, looking to make it run again.
    What would be the best thing to spend a few dollars on?

    Is the RPM/Holley combo possible as is, or with a new cam?

    Or does the compression ratio need to be improved first?
    With possibly a used set of heads.

    My understanding is a set of closed chambered heads would raise the compression ratio. I have a set of 915s, however one of the 915s was machined below the springs and spacers used. I have the valves, springs, shims, etc, to put them back together but beyond my skill level, and not sure if it is even realistic.
     
  2. joshcook81

    joshcook81 Well-Known Member

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    I’d pull the valley pan and take a look at the condition of the cam. I’d also pull the oil pan and take a look.. make sure cylinder walls look good and there’s no metal shavings in the pan. The 346 heads aren’t bad heads. I have them on my 72 383. From what I understand the close chamber heads will raise compression.
     
    Last edited: Nov 24, 2018
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    • rumblefish360

      rumblefish360 so close yet so far away

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      If this was my mill and since you asked the question of what would I do... which is also dependent of the wallet thickness.... with the “budget is the theme” in mind.

      I’d use the rpm and 750.
      Run a new cam that fits the build goal.
      Unless you can identify the cam in there now and it’s OK with you and it’s use. I would look into a new mechanical cam that works with the cars weight/gear/tire and goal, because it is a manual trans car.

      If head milling isn’t much for the wallet.... I’d look at no more than a full point increase, which would be a lot! An actual 9.0-1 is very good.

      What is your cars weight, rear gear and tire size?
       
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      • matthon

        matthon Well-Known Member

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        62 Dart, just over 3k pounds, 3.23 rear, 15 inch tires.
        We're talking milling the heads, right? Would that involve milling the intake as well?

        What changed from 70 to 71 to lower compression in the 383?
         
      • sr71mopar

        sr71mopar currently moparless

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        .
         
      • 383Scampman

        383Scampman Well-Known Member

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        What changed from '70 to '71 to change compression is the height of the piston from the wrist pin to the top of the piston . Headwork and cam will give you the best return . The M.P. selection of cams are about the best cams for street use. Use factory valve train parts with it . Your heads are fine (open chamber). Closed chamber are 915 (closed chamber , 78.5 cc chambers). They are getting hard t o find and expensive . The cutoff point on iron heads is about $650.00 . Above that go with aluminum ones .
         
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        • matthon

          matthon Well-Known Member

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          These are the 915s I have. When I had my other 383 done at a machine shop they took them apart. Came back with springs, retainers, valves, and spacers in a box. Not sure why the spring areas look different on each head, or the purpose of the spring spacers.
          I ended up going with aluminum heads on that engine.

          I have the valves and springs. A friend looked at them and said the valves looked like someone spent some money on them, and the springs were hefty, I forget the exact terms he used, he definitely knew more than me.

          Do these heads need professional help, or can any idiot, like me, put these back together?

          20181009_210922.jpg

          20181009_210955.jpg
           
          Last edited: Nov 24, 2018
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          • rumblefish360

            rumblefish360 so close yet so far away

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            Yes.
            Depends on how far you mill the heads down.
             
          • RustyRatRod

            RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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            If it's an HP, it has the "Road Runner" cam, which is a great cam. If that engine is in good condition, bolt that sumbitch in and go. How's that for budget?
             
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            • matthon

              matthon Well-Known Member

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              On second thought, I think I do care if it's cast or forged. I have a neutral balance flywheel I wanted to use, but cast is externally balanced.
              From the one horrible pic I have, it looks like the "cut ring" style for forged.

              20181125_125928.jpg
               
            • matthon

              matthon Well-Known Member

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              C = Special crankshaft + pistons

              What's that mean exactly?

              20181125_191452.jpg
               
            • txstang84

              txstang84 Well-Known Member

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              Doesn't that iron cross mean there's an oddball bearing size mixed in or something?
               
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              • 383Scampman

                383Scampman Well-Known Member

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                The Maltese cross on any mopar engine indicates undersize main OR rod bearings .
                 
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                • Kernel Sanders

                  Kernel Sanders eating chicken wings and drinking beer

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                  I do believe the last year for the 383 in cars was 71 and the engine was externally balanced as it had a cast crank IIRC
                   
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                  • matthon

                    matthon Well-Known Member

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                    This is what I discovered.

                    HP for 1971 means High Performance, labeled a Magnum or Super Commando engine, for a 1971 Road Runner/'Cuda/Challenger/Charger/Super Bee, with a Holley 4 barrel, 8.5:1 compression, 300 gross horsepower, 410 gross torque.

                    Basically, HP was for the engine in the super cars of the day, not granny's station wagon.

                    It also seems to make sense what Allpar has listed regarding the crank, that starting in 1971, the cast iron 383 crankshaft was used as a cost saving measure on automatic-transmission cars.
                    HP or not, in 1971, a forged crank was used if it's for a 4 speed. The chart on Allpar shows the 1971 383 had a Holley 4 barrel and was standard in the Road Runner and 'Cuda. Only year for gross and net numbers.

                    1970 had two HP 383s, both with 9.5:1 and a four barrel, one with a Holley. There was also an 8.7:1 non-HP 383 with a two barrel.
                    1971 had one HP 383 with 8.5:1 and a Holley 4 barrel. There was also a two barrel non-HP 383 with the same 8.5:1.
                    Starting in 1970 compression was lowered, to cut back on emissions, and to run on regular gas, meaning lower octane gasoline, not unleaded fuel.
                    Starting in 1973, exhaust-valve seats were induction-hardened to allow use of lead-free fuels.
                     
                  • rumblefish360

                    rumblefish360 so close yet so far away

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                    I neverheard of an external balnced 383. Now a 400 may have been.
                     
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                    • IQ52

                      IQ52 Well-Known Member

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                      The '71 383 2-bbl was a cast crank engine. The HP engines should have had a forged crank shaft
                       
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                      • oldkimmer

                        oldkimmer FABO Gold Member FABO Gold Member

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                        The 1971 2 barrel 383 had a cast crank, but it was NOT externally balanced. Kim
                         
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                        • IQ52

                          IQ52 Well-Known Member

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                          Beggin" yer pardon, but the '71 383 2bbl I had was very definitely externally balanced. I pulled the original engine from the original car.
                           
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                          • 440 Mike

                            440 Mike Well-Known Member

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                            Most production 383's never reached the advertised compression ratio. The closed chamber heads (if the pistons are below the deck) and new cam with matched springs would be a great start.
                             
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                            • matthon

                              matthon Well-Known Member

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                              More crappy pics. More dirty from sitting than anything. Spent it's time collecting dust in a heated garage.
                              It turns freely back and forth, but I didn't go to far, put it on a stand, some oil in the cylinders, spun it around, put the plugs back in it, until I can get to it.
                              It's pretty complete, but I don't need the intake, pan/pickup, or motor mounts.

                              20181125_172332.jpg

                              20181125_172643.jpg
                               
                            • IQ52

                              IQ52 Well-Known Member

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                              Man-oh-man! Mickey Thompson valve covers. Otta be worth sum 30 horse.
                               
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                              • matthon

                                matthon Well-Known Member

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                                If cool factor gets you a second or two, anything is possible.

                                20170801_081807.jpg
                                 
                              • Bighead440

                                Bighead440 Well-Known Member

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                                2bbl is possible to be cast but I have never seen a 4bbl 383 that was cast. I had a 71 Sport Fury 2bbl and it was cast, and that's the only one I've ever seen. Also have seen many 73-up auto trans 440s with steel cranks, so you never know!
                                 
                              • Bighead440

                                Bighead440 Well-Known Member

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                                With some head milling and a thin head gasket (steel shim .018") you can use a 275DE comp cam, especially with exhaust manifolds, with that 3.23 gear and an 11" converter (318 pickup 727 unit, for example) and any factory 4bbl setup and make killer power and sounds lopey. Use Comp 911-16 (drop in) valve springs or FRESH red HP factory (damper) springs and stock rockers. Cheep and effective.
                                 
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