1970 Dodge Dart 318 upgrades

Discussion in 'Small Block Mopar Engine' started by PikaPhantom, Jun 28, 2018.

  1. PikaPhantom

    PikaPhantom Well-Known Member

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    Hi all, I am playing with thoughts of upgrading from a stock camshaft to something that is a nice streetable upgrade for an entirely stock engine, highway gears, and exhaust system. I am still learning so I'm not entirely familiar with the specs and technicalities of camshafts so I'm not sure what I should be looking for. The engine is currently out of the car for a rebuild so figured now would be the best time to do this. I will be sticking to the stock two barrel carburetor as well untill I have enough funds for a four barrel swap.
    I was thinking of a mild cam like this COMP Cams 20-210-2: High Energy 260H Hydraulic Flat Tappet Camshaft Lift: .440" /.440" Duration: 260°/260° RPM Range: 1200-5200 | JEGS which was suggested by a friend who definitely has way more knowledge on this stuff than i do. I realized i did not include this part which is a blunder on my end, sorry.
    but how would something like this cooperate with my current set up as a slight upgrade over stock and a stepping stone for future upgrades and would I need new valve springs.
    thank you
     
    Last edited: Jun 28, 2018
  2. Alaskan_TA

    Alaskan_TA Well-Known Member

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    I have a stock 1970 Valiant with a 318 & I love driving it just as it is.
     
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    • Dartswinger70

      Dartswinger70 Well-Known Member

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      Summit has a affordable cam, I forget what number it is, I put it in a 318 and a 340...I think its this one
      Summit Racing® Cam Kits SUM-K50062

      This one is a little more mild:
      Summit Racing® Classic Cam and Lifter Kits SUM-K6900
       
    • toolmanmike

      toolmanmike FABO Staff Staff Member FABO Gold Member

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      • 72Dart6pack

        72Dart6pack Harder Better Faster Stronger.

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        This is a 2 bbl. Go with something like this.

        20160404_195801.jpg
         
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        • TrailBeast

          TrailBeast Slightly Twisted Member

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          A 2&2&2 barrel.:D
           
        • AJ/FormS

          AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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          If you want to pursue this, It is highly advised to bump up your compression first, and co-ordinate with the cam's Intake Closing Angle with your available gasoline's octane rating, your intended usage, and the available TM (Torque Multiplication), and most especially, with your budget. It's very easy with a 318 and a small budget to quickly get in over your head.

          For instance
          If you intend or are constrained by budget, to keep the factory low-stall TC and hiway gears, Then your factory engine cannot take much of a cam, before it rapidly becomes a turd from idle to maybe 3000 rpm. With 2.76 gears, this is apt to be well over 30 mph. This is the definition of turd; Slow to 30 mph..With 2.45s you are in deep doggy doo-doo.

          Because you state the small budget requires you to keep the 2bbl, You are between a rock and a hard place; and because your knowledge base is still at newbe level ( this is not a poke btw), it would be strongly advise to not play with camshafting..... until your further up the learning curve.
          BUT, this is very important, until that time, it would still be adviseable to up the compression today, in preparation for that future opportunity.
          To that end, let your builder get the flat-top pistons up as high as he can towards zero deck, and call it done. Depending on the size of your chambers, this could net you a compression ratio between 9.0 and 10.0. From the final compression ratio, in that range, you will be able to find a cam to satisfy your 2bbl hiway locomotive.
          Here's the caveat, and the key; do not order a cam until you know exactly where the compression ratio will come in at. Then shoot for an altitude corrected Dynamic compression ratio a little lower than 8.0,with a cylinder pressure around or a tad under 160, and you will be a happy camper.

          Secret; the higher your Static compression ratio is, the larger your camshaft can be...... but the larger the camshaft is, the later the power comes in, so the sooner you need a hi-stall and possibly gears. This is why, on a tight budget, you can quickly get into a turd combo.
          When money is not a concern, you can build a 318-powered A-body, to blow a factory 340-powered one, away.
          The high-compression 2-bbl 318, is the building block.
          Unfortunately, you cannot go much higher in compression with the factory cam, before you run into detonation, which must be avoided at all costs. This puts you into the ugly place of having to run top-grade gas and possible reduced timing, and then with the lower timing,the little 318 just runs out of performance,while costing big money to continue operating, and then you have a big disappointment.
          You are at the crossroads of doing both a compression bump and a camswap together, a very enviable place for a lot of guys. Take advantage of it; do not let that engine come home at 8/1 Scr.
           
          Last edited: Jun 28, 2018
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          • PikaPhantom

            PikaPhantom Well-Known Member

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            I was thinking of a mild cam like this COMP Cams 20-210-2: High Energy 260H Hydraulic Flat Tappet Camshaft Lift: .440" /.440" Duration: 260°/260° RPM Range: 1200-5200 | JEGS which was suggested by a friend who definitely has way more knowledge on this stuff than i do. I realized i did not include this part which is a blunder on my end, sorry.
            but how would something like this cooperate with my current set up as a slight upgrade over stock and a stepping stone for future upgrades and would I need new valve springs.
            thank you
             
            Last edited: Jun 28, 2018
          • 318willrun

            318willrun Stomper 4x4... we kept energizer in business

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            • rumblefish360

              rumblefish360 so close yet so far away

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              Your such a joker AJ. He already said... ehhhh, never mind, re read his post on what he admits he doesn’t know.

              Nothing like introducing rocket science to a new guy that only has watched them take off.
               
              Last edited: Jun 28, 2018
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              • rumblefish360

                rumblefish360 so close yet so far away

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                While that isn’t a bad first step cam, what we really need is some information on what your car already has and what your willing to do with it. Let’s start at..... well, at the start. Square one.

                Know what you have first!

                Do you know what transmission you have?
                Do you know what gears the rear end has?
                Tire size?
                Are you willing to swap out the rear gears? Or the torque converter? Is there a target goal in mind? Track ET wise or say, an est. 275 hp?

                Are headers in your future?
                 
              • nm9stheham

                nm9stheham Well-Known Member

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                OP, this may sound like a sily questioh, but you'd be surprised how differently engine builds can go, depending on the end goals. What are your goals and planned uses for the car and engine over the long term? If you are on a budget, then that long term goal should be front and center so that you don't waste $$ going down the wrong road, IMHO.
                And what work is bring planned in your rebuild? The point about higher compression pistons is on the table in a rebuild, and is a step forward for your 318... its weakest attribute is low compression.
                 
              • PikaPhantom

                PikaPhantom Well-Known Member

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                Everything is completely stock. 904 Automatic torqueflite transmission. Highway gears. Tires sizes are currently 205-70r-14 in the front 215-70r-14 in the rear. I have no intention of swapping gears or the torque converter.
                 
              • PikaPhantom

                PikaPhantom Well-Known Member

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                Well right now the goal is just to make it daily driveable and keep it that way. I guess this is more of an engine refresh than a complete rebuild. I am not wanting to get out of hand with high end performance parts but in my head I figured it would be better to a camshaft replacement now with something that would make the car run better rather than go through the trouble of pulling the engine apart again in the future and replace it if it should come to that.
                 
              • rumblefish360

                rumblefish360 so close yet so far away

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                Well, the cams duration @.050 is 212. It can use the stock converter no problem and the “Hwy. gears” are a bit steep for it but more than likely, passable with the stock tire size.

                In all honesty if I was going to use that cam, I’d like to use at least a 3.23 gear ratio. The 2.94 might be passable. If you have the 2.76 ratio, well, I don’t think I’d use that cam. I’d look for one cam size smaller.

                Other than that, a factory 4bbl. carb and intake would do very well. Dual exhaust off of the stock manifolds would be very good to do. Install an AB pipe if possible.

                Once all of those parts are in place, it should run very well and be a pleasure to drive.
                 
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                • PikaPhantom

                  PikaPhantom Well-Known Member

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                  Would you happen to know where i could find the gear ratios? I'm looking at spec sheets Captcha here and I'm not entirely sure what if what I'm looking at is correct under drivetrain or whether I need to be looking for something else. Also just to clarify, whether I'm running the cam I asked about or one size smaller would running it on the stock 2 barrel carburetor and intake cause any issues.

                  thank you
                   
                • rumblefish360

                  rumblefish360 so close yet so far away

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                  You can run almost ANY cam on a OE 2bbl Cam and intake. How much it will limit the performance potential is another story. But you’ll know when you add a good intake and carb!

                  There was a tag installed at the factory with the gear ratio stamped on it. This tag could still be attached to one of the bolts that hold the rear ends cover on. However, RUST may have taken it away.

                  The only other way I know how to Absolutely identify the rear end gear ratio is to take the cover off and find the gear ratio stamped on the side of the ring gear. You’ll need to jack up both sides of the car and suspend the rear wheel in the air. With the front tires chocked to prevent the car from rolling forward or backwards, rotate the wheel until you find the ratio stamping.
                  2.76 - 2.94 - 3.21 - 3.55 etc...

                  Get a new cover gasket and a couple of quarts of gear oil to refill the rear. I use the Mobil 1 synth. 75/140 by itself, no issues. No additive needed.
                   
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                  • MrJLR

                    MrJLR Built, not bought FABO Gold Member

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                  • PikaPhantom

                    PikaPhantom Well-Known Member

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                    cheers friend. Much appreciated thank you
                     
                  • Dartswinger70

                    Dartswinger70 Well-Known Member

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                    Man, I threw my 318 together in the early 2000's for under a grand. Didn't get scientific, gaskets and overhaul kit, ran the Summit cam, Edelbrock intake and a Holley, and it was fine. Stock heads also. Some of us aren't scientists, you throw the shit together and run it, there is no drawing board.
                     
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                    • toolmanmike

                      toolmanmike FABO Staff Staff Member FABO Gold Member

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                      Bottom line here: Don't go too big with a cam. Stock 318 2 barrel cars can't stand too much of a increase without adding a 4 barrel, dual exhaust, converter, and rear gears. The cam you choose might not be that much bigger than the stock one and will be a lot of extra expense for not much gain. I have the same combination as you have. I already have duals and I switched the gears to a 3:23. It runs good and I get almost 20mpg/hwy. The next will be a 4 barrel and intake. I may stop there.
                       
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                      • 66jim

                        66jim Well-Known Member

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                        Get a used factory 340 cam and matching lifters somewhere? ( I have ) new timing chain (Summit) advanced 4 deg. CHEAP you will be happy
                         
                      • rumblefish360

                        rumblefish360 so close yet so far away

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                        Factory 340 cam sells at or around $300.
                        I think we can all skip that cost.
                         
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                        • AJ/FormS

                          AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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                          I got about 4 used ones
                           
                        • Dartswinger70

                          Dartswinger70 Well-Known Member

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                          Is that the fabled '68 340 4 speed" cam?...