Comp XE270S experiences?

Small Block Mopar Engine

  1. 1966Post

    1966Post Well-Known Member

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    In process of building a .040 over 360 plan is 9.25-9.5 compression Speedmaster aluminum heads. I'm a solid flat-tappet cam user. Looking at the
    Basic Operating RPM Range:
    1,800-5,800
    Intake Duration at 050 inch Lift:
    224
    Exhaust Duration at 050 inch Lift:
    224
    Duration at 050 inch Lift:
    224 int./224 exh.
    Advertised Intake Duration:
    270
    Advertised Exhaust Duration:
    270
    Advertised Duration:
    270 int./270 exh.
    Intake Valve Lift with Factory Rocker Arm Ratio:
    0.468 in.
    Exhaust Valve Lift with Factory Rocker Arm Ratio:
    0.468 in.
    Valve Lift with Factory Rocker Arm Ratio:
    0.468 int./0.468 exh.
    Lobe Separation (degrees):
    110
    No track use planned so this is the largest cam size I'm considering for driveability
    I've used the Isky E4's in a few 318 builds that turned out very well but feel I need something a bit larger for the 360 platform

    Thanks in advance and Happy 4th all
     
  2. harrisonm

    harrisonm Well-Known Member

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    I have the XE 268 in my 69 Barracuda 340. It is an awesome cam. As much as I like it, I can only imagine how much better the 270 would be. I have great low end power, and a mean sounding idle.
     
  3. PRH

    PRH Well-Known Member

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    The Comp “270S”(part number 20-246-4) is not part of the XE, or in the case of solid cams, “XS” family.
    It uses the older Magnum solid lobes.

    It would be fine in your application, but you’d probably be leaving a little power on the table compared to the XS equivalent.

    A 224@.050 cam using lobes from the XS family would have to be a custom.
    The smallest XS shelf cam they offer for a SBM is 230/236@.050.
     
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    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      You're right...but it can be argued that no matter what cam he chooses, he's leaving power on the table, as there really is no "perfect" choice. That 270s has slow ramps compared to modern stuff and will be dead nuts reliable, not beat the snot out of the valve train and last forever.
       
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      • volaredon

        volaredon Well-Known Member

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        Junk the 360, 318 will do ya.
        Sorry had to.
         
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        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          Or even a slant. LMAO
           
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          • 1966Post

            1966Post Well-Known Member

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            Go big or go home is my motto…
             
          • krazykuda

            krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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            That's what she said.... :D
             
          • 1966Post

            1966Post Well-Known Member

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            Ha!
             
          • 4spdragtop

            4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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            We have the 270S in our 273. Sounds great, but falls flat on its face lol. That's my fault for putting that kit in the 273. I'm building another sb for it lol.
             
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            • AJ/FormS

              AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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              I can confirm, that the 224/224/110 solid will be a barrel of street fun, with a potential to make great fuel-economy.
              I ran a Hughes FTH 223/230/110 and absolutely loved it; mind you, at over 185psi, and 11.3Scr, still on 87E10.. Best combo I ever had. I was very sad when the lobes ended up in the pan.

              With alloy heads you can run a lotta cylinder pressure. You paid big money for those, so, why
              not take advantage of that fact. Jus saying is all.
               
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              • 1966Post

                1966Post Well-Known Member

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                Thank you AJ. I was hoping you’d weigh in.
                I’m looking forward to it as well
                 
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                Ok, maybe not best, but for sure my favorite,lol.
                 
              • dartfreak75

                dartfreak75 Restore it, Dont part it! FABO Gold Member

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                I like the 702 voodoo cam. Very similar in duration 265/271 but with more lift .475/.495 and a 112 LS nothing against comp i just perfer the dual profile cams and I like the 112 LS for street use.
                 
              • Bighead440

                Bighead440 Well-Known Member

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                I have one (270S Comp) in my .060" over 318 (328") with modified "302" heads (360 valves, gasket matching, deshrouding, milling, etc.) and it runs fantastic! Used #901 Comp springs and stock 273 valve gear. Idles at 750rpm with a great little lope, pulls maybe 14"hg vacuum with a 625 Street Demon and Street Dominator small port intake. Used 2.5" collector long tube headers with a Flowmaster merge Y-pipe and a single 3" FlowTech Afterburner muffler and tailpipe. Gets 20mpg with an 833 O/D gearbox and 3.55 gears on the highway, too. Should be really mild in any 360 and work nice even with dished pistons.
                 
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                • K.O. SWINGER

                  K.O. SWINGER Meeting in the alley since 1976

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                  I didn't see where you mentioned gear ratio or transmission type. At 224@50 on 110 you will start to feel the bottom end soften up a noticeable increased mid-range and a little more top end so 3:55 gears would be appropriate anything taller might not be a good fit.
                   
                • Bewy

                  Bewy Well-Known Member

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                  That sounds like the #20-246-4 cam that had 'variable' duration.
                  The adv duration can be changed by 10 degrees by changing the lash from 0.015" - 0.030".

                  So you have some adjustment you can play with.
                   
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                  • dirty white boy

                    dirty white boy 50 yr old Juvenal delinquent

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                    thats real close to what im putting together now sept with a lil bigger hydraulic roller in a factory roller cam block, same intake n heads with alotta home porting 750dp carb, 3000 stall going in a 73 duster, got about 650 buck in it all so far....
                     
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                    • Bighead440

                      Bighead440 Well-Known Member

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                      Yes^^^this! I have tried it as tight as .014/.016" hot and as loose as .024/.026" hot and it does make a slight noticeable difference.
                       
                    • Bighead440

                      Bighead440 Well-Known Member

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                      I felt bad using a flat tappet in my ('87) block, but it had always been a hyd flat tappet (stock 2bbl truck, later a .430/.450" Purple hydraulic), and all the roller cams I had then were in use or obligated to other builds. You're gonna love that Duster, I did a '92 Jeep 5.2L Magnum for my '68 Dart and used a 218/224*@.050" Comp roller (custom back then, now a XR270HR-10) and ran as low as 8.20s at 86mph in the 1/8mi. I had a tight converter which was killing my 60ft. times, so depending on your cam, you may need a tight 9.5 or 10" converter, mine was 11"....
                       
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                      • 1966Post

                        1966Post Well-Known Member

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                        Thanks for all the experiences, replies feedback and "get a 318" comments so far!
                        Vehicle is a '85 D150 32k original mile /6 A833OD trans 3.50 gear 8 1/4 rear. I bought the truck last spring and drove it with the /6 all summer pretty meeger power but very good on fuel consumption.. Over the winter I installed a 30k mile 360 I got from a motorhome put a timing chain, pan and valve cover gaskets and 69 340 avs intake with a 650avs2 carb I dialed in
                        I have a 75 360 that will be building block for this engine have a set of the Speedmaster aluminum heads and at the time I bought them you got a free airgap knock-off intake probalby going wih the Sealed power 116cp pistons I have a few sets of 273 rockers and bananna grove shafts but would rather find some Isky or Crane 1.5's and probably get a set or Rockets heavy duty shafts I have several different sets of head gaskets to play with to get the quench and compression where I'd like it. Again shooting for a 9.25-9.5 compession ratio I've always been a fan of solid lifter cams in my engines. Thanks again all and FABO
                         
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                        • silverex

                          silverex Well-Known Member

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                          Got one 270s in my 360 0.40 over.
                          -performer rpm intake , 600 cfm carb,j head full ported 1.6 roller rocker, 10.5 comp. 3.91 gear and 904
                          90% street use love it. Idle sound is really good
                          Still run A/C and have more vaccum that I want.

                          Car as run 13.20 full weight car
                           
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                          • Bighead440

                            Bighead440 Well-Known Member

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                            Identical truck to mine, besides the condition I'm sure, mine is well worn. LOL. I added a 9.25 rear because I had it and it was Sure Grip with the same 3.55 ratio, and a friend with a 2.93 geared 8.25" truck had a bad axle, so he helped me with the swap(s) and I gave it to him. But mine was a heater-only, manual steering shortbed fleetside '85 slant-6 rig. Don't hesitate to use the 273s, they work as good as any Crane/Isky iron rockers in such an application with single springs. You can upgrade to locking adjusters if your self-locking ones are a lil loose.
                             
                          • 1966Post

                            1966Post Well-Known Member

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                            Thanks for the note I got pretty lucky on this one mines an 8ft bed the truck is super clean but I like those short beds!
                             
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                            • Bighead440

                              Bighead440 Well-Known Member

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