Purpleshaft .484 Cam in a 273?

Discussion in 'Small Block Mopar Engine' started by 64 SRT8 Dart, Aug 12, 2017.

  1. 64 SRT8 Dart

    64 SRT8 Dart Well-Known Member

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    Anyone ever run the .484/.484 purpleshaft cam in a 273?
    If so, how'd she run?
    I have the old 273 out of the Valiant just laying around and may just build it just to build it.
    I mean I would put a diff intake/carb on it and do some mild head work, but...wonder how it would run?

    I can pick one up new for $40 at the moment. Lol
     
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    • SGBARRACUDA

      SGBARRACUDA ROY FABO Gold Member

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      I ran a .284/ .484 MP cam in a 70 340 installed @104 degrees. It was pretty radical in a 340 but pulled really well. I would think it would be a bit to much in a 273.
       
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      • 64 SRT8 Dart

        64 SRT8 Dart Well-Known Member

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        What kind of converter you use or was it a 4spd?
        I couldn't find the duration @.050, do you know what it may be? 240ish or something?
        Also I think I saw the power range is something like 2800-6500?
         
      • 70aarcuda

        70aarcuda Master Hoader of SBM FABO Gold Member

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        suppose to be 241 @ .050
         
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        • 318willrun

          318willrun Stomper 4x4... we kept energizer in business FABO Gold Member

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          I ran that cam in a 360. Ran good. Never tried in a 273. Do it and let us know... :)
           
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          • SGBARRACUDA

            SGBARRACUDA ROY FABO Gold Member

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            I had it in a 1970 340 4speed Duster with 4.30 gears. yeah it has 241 @ 50 duration.
             
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            • 64 SRT8 Dart

              64 SRT8 Dart Well-Known Member

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              My block is over at my father in laws at the moment and I'm going to pick it up tomorrow. It needs hot tanked, new cam bearings and at least .030 over bore.
              I figured I may do this as a side project for something to do as the $$$ frees up. Lol
              Wonder how that cam would react with a turbo?
              Also I know there's limited pistons especially forged out in the market.
              I just think it would be neat to see what kind of power the little guy could make for grins and giggles, lol.

              I even have the 904 it was mated to that I've been itching to build, lol.
               
            • yellow rose

              yellow rose Doctor of Thinkology.

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              Not the right cam for a turbo.

              Put the cam in at 102 and let it rip.
               
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              • A/MP

                A/MP Well-Known Member

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                The factory D Dart Cam had a .504 lift. That 340 cam is fine. Turbo would be a waste with the small cc, intake valve and intake runners. But you can pressurize anything and make HP. 273 responds with higher compression. My last NA 273 made 390 HP. I have some new pistons 10.5 and 12.0 if interested.
                 
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                • 273

                  273 Well-Known Member

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                  There's a couple of guys on here running large cammed 273 and seem happy with them. Ones also running a tunnel ram too.

                  Conventional wisdom says that cam is way too huge for a 273 but i dont think most take into account head flow. 273 and 340 have similar head flow to cid ratio. So in my theory it should take similar amount of cam degrees at same rpm to fill the cylinders in other words should act similar in a 273 as in a 340. But your gonna fall into the main problem with building a 273 or any small engine is they need a lot more gear than a similar built 340/360. Plus a lack of CR and stall ain't gonna help with this cam.
                   
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                  • Oldschoolcuda

                    Oldschoolcuda Early-A Body Nerd FABO Gold Member

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                    Do it.
                    With a little head work and decent compression a 273 will love that cam. Like 273 said run at least a 3.91.
                    My darts 273 has a 508 purpleshaft and shits & gets with 4.10's.
                     
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                    • nm9stheham

                      nm9stheham Well-Known Member

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                      If you are putting in 2 BBL, lower compression pistons and the later open chamber heads, the static CR is gonna start low and the dynamic CR is gonna drop pretty badly with this cam. Low end grunt will not be good at all.... IMHO, to make up for this partially, mill the heads to get the chambers down in the low 60's or high 50's cc range and use the higher CR pistons. Advance the cam some as suggested.

                      BTW, how would you be using this engine? A lot of how you think it turns out will be in how you use it, and a lot of subjective judgments on how you like things to run; high revs will be the name of the game here.... which goes with the gearing comments.

                      IMHO again, a turbo would be GREAT here but this is totally the wrong type of cam.... waaaay too much overlap is the main problem. If you do consider this, then the lower compression is ideal; stay down in the 8:1 Static CR range, and limit boost to around 10 psi tops. Since finding forged pistons is not gonna happen and you will have cast pistons, then the pressure needs to be limited for reliability. Turbo selection will become the key to the low end response; in that case, less is more.
                       
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                      • 64 SRT8 Dart

                        64 SRT8 Dart Well-Known Member

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                        Motor would be basically hot street/drag.
                         
                      • 64 SRT8 Dart

                        64 SRT8 Dart Well-Known Member

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                        Wonder what a good turbo cam would look like for numbers?
                         
                      • 64 SRT8 Dart

                        64 SRT8 Dart Well-Known Member

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                        Are they forged?
                         
                      • nm9stheham

                        nm9stheham Well-Known Member

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                        Well, then you could maybe get away with a higher gearing, higher stall TC, and go with a bigger cam. It does not sound like you are too concerned about nice low end torque and pulling away smoothly from a stop sign... .more like tearing out from a stop sign, tires smoking every time LOL. I'd still be upping the CR though....
                         
                      • JBurch

                        JBurch Well-Known Member

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                        Check out this link:
                        Another piston option for the 273.

                        Ages ago, in an Issue of "Mopar Action" was a story of a 67 Dart, 273 that went 10's called "Darn Dart". Simple build, TRW pop up pistons, X heads, 509 MP camshaft, don't remember carb or intake.

                        To make it work, it needs compression...........
                         
                      • AJ/FormS

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

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                        I had the 292/508/108 in my 360. That's the next bigger size. I yanked it before the summer was out. It needed 4.30s with the 2.66 low 4-speed I was running. And I had to slip it out like a gutless Mustang; even with 11.3 static cr.
                        40 bucks is 39.95 too much.

                        Check this out! Your 284Cam in at 102*
                        Static compression ratio of 10.25:1.
                        Effective stroke is 2.57 inches.
                        Your dynamic compression ratio is 8.17:1 .
                        Your dynamic cranking pressure is 164.30 PSI.
                        V/P (Volume to Pressure Index) is 106
                        Here we have the Scr set to achieve the maximum Dcr and pressure for pump gas;And the VP is down in slanty territory.
                        A good strong street VP to have is like 150ish. A 410 stroker with a small street cam pulls around 165.

                        Here is the turd I was running; 292/508/108 cam in at 104
                        Static compression ratio of 11.3:1.
                        Effective stroke is 2.64 inches.
                        Your dynamic compression ratio is 8.60:1 (aluminum heads).
                        Your dynamic cranking pressure is 175.57 PSI.
                        V/P (Volume to Pressure Index) is 143
                        I call it a turd cuz the bottom end was so soft that I had to run 4.30s to satisfy that, which made hiway cruising very uncomfortable, and I live 20 minutes from the closest next town. It ran great, awesome even, from 5000 to 7200

                        I replaced that cam almost right away with this one, a 270/276/110 in at 106
                        Static compression ratio of 10.9:1.
                        Effective stroke is 2.86 inches.
                        Your dynamic compression ratio is 8.91:1 .
                        Your dynamic cranking pressure is 183.76 PSI.
                        V/P (Volume to Pressure Index) is 162

                        This pulled 2.76s like nothing.

                        I currently run a 276/286/110, and it looks like this
                        Static compression ratio of 10.9:1.
                        Effective stroke is 2.79 inches.
                        Your dynamic compression ratio is 8.72:1 .
                        Your dynamic cranking pressure is 178.73 PSI.
                        V/P (Volume to Pressure Index) is 153

                        Notice the progression in VP: 143 was soft,162 was very strong, and 153 is up the middle.
                        153 is a good compromise for a 360 having enough to pull a starter gear of 9 or 10, yet lots of top end to pull 6500rpm with a good amount of power. Free flowing heads and exhaust lets her wind out to 7000 easily enough.

                        In a 273 IDK, but I for one wouldn't consider a 284.......at all. I wouldn't pay a nickle for it. There are just too many compromises needed to satisfy it. Compromises like,
                        With an automatic; a very-high stall TC, and at least 3.91s to get the rpm up.
                        And with a stick-car; a lot of clutch slipping to get moving, and even more gear, to get the rpm up where it needs to be, cuz you don't have a TC for TM help.

                        Now in an earlyA, you can get away with a bit more cam, or less gear, on account of the weight difference. At the time I had the 292 my raceweight was 3650-me in it. The EarlyAs would probably be 400ish less. Currently I am at 3467 me in it, hence the smaller cam is all I need.And I run the 3.09 low trans so my starter gear is up to 10.97. All problems solved.

                        Good luck with whatever you choose
                         
                        Last edited: Aug 14, 2017