Comp cams xe268h for 318

Small Block Mopar Engine

  1. nm9stheham

    nm9stheham Well-Known Member

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    This all gets to what works for the generic Mopar hot-rodder. Comp's data and the Wallace tool(s) are the easiest way for newcomers to tackle the DCR computation. (IF the static CR is well known, which is another Wallace tool.)

    This gets to a point in the cam specs that helps Comp.... they PUBLISH the ICA clearly in their website literature. Who else does that? So when someone such as DartFreak starts to learn this, they ask the same question as in post #230: where do you get the ICA? With no cam card in-hand, and no ICA listed in the published literature for Howards, Lunati, Crane, Hughes, Racer Brown, etc., Comp becomes the easy de-facto website to go to. No surprise then that DF looks at Comp's cams. Yeah, it may not be the best choice for other reasons, but making it easy is what Comp does better than any other MFR.

    Cam specs are confusing for most newcomers. Computing the ICA from LSA and advertised duration is another step of learning. AJ lays it all out in post #236, but I can see many despairing at the thought of pulling out a calculator. It needs to be in an app to get folks to adopt this thinking more.

    The DCR tool that I like does the ICA computation for you in a simple visual tool, including static CR computation. But then, like for the case shown by DF's situation with no PC, it is not directly available as an app for a Smartphone. (I have not tried to run it on mine but it looks like it might work.)

    DF, have you tried that download and running the tool that I linked, on your Smartphone?
     
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    • nm9stheham

      nm9stheham Well-Known Member

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      That's what I thought...what weeeere they thinking? LOL
       
    • dartfreak75

      dartfreak75 Restore it, Dont part it! FABO Gold Member

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      Yea I did it said I needed some file reader or something!!? Let me try again and I will let you know what it says. Oh btw I went to Hughes engines website last night and started looking at there cams. Idk if I will go thought route but I'm looking. The comp xe262h is looking pretty tempting. I also like the xe256h and the luniti voodoo 701 or 702
       
    • dartfreak75

      dartfreak75 Restore it, Dont part it! FABO Gold Member

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      Ok so I tried again it says I have to download winzip I'm gonna try to download that and see if it will work
       
    • Wyrmrider

      Wyrmrider FABO Gold Member FABO Gold Member

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      dart
      problem with Hughes is that they do not give you seat timing so really hard to tell if soft or steep ramps or what the ICIA might be
      on those short comp cams
      just go to the small block chevy page and see if they have exactly the same duration, lift and lca there
      if so pass
      with a MOPAR cam like the voodoo you have a choice of a shorter duration, earlier ICA for similar lift, or greater lift (area under the curve) at the same duration/ ICA
      and that's only half the problem
      a short rod motor like a chevy needs a different lobe center and ICA and ex open and intake open and exhaust close than a long rod motor like a mopar.
      If you have ever seen a master for an automatic cam grinder there is a master for each lobe
      to change the lobe centers takes some of the automatic out of it
      You have to grind all the intakes then reset the gang master for the exhausts, and some grinders require a different master
      same problem if you want a different exhaust lobe than what the catalog calls for (with and without headers for example, )
      if you do see the same cam for a sbc and mopar you can do better- just use comp for a starting off point
      if you have low compression look at a voodoo or Howard with the (15) footnote and think about using one size shorter cam and you will find more lift anyway
      cheers
       
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      • dartfreak75

        dartfreak75 Restore it, Dont part it! FABO Gold Member

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        I tried it again it's a no go even with the winzip it says file corrupted. Tried it three times
         
      • Coronet 500

        Coronet 500 Well-Known Member

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        I ran the XE 256 H in a 318 same as you have in a truck with 3.55 gears and small Street Demon . It had amazing low end grunt and surprising top end.
         
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        • nm9stheham

          nm9stheham Well-Known Member

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          Thanks very much for trying, DF...... just thought it would be worth a shot. Do you have and Apple or Android device, BTW? If you need and help with figuring up ICA's, or checking your numbers, let me know or use AJ's formulas. Always glad to try to help.

          If I knew how to write apps for Apple and Android, it would be in the works. But beyond my abilities....
           
          Last edited: Oct 6, 2018
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          • dartfreak75

            dartfreak75 Restore it, Dont part it! FABO Gold Member

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            I'm trying really hard to decide between it and the xe262h. I'm leaning more toward the 262 just because I have the lower gears to install later I think it really liven it up with the 373. How do you like the street demon? I'm seriously considering one. What intake did you run?
             
          • dartfreak75

            dartfreak75 Restore it, Dont part it! FABO Gold Member

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            I will download it on my wife's laptop!
             
          • dartfreak75

            dartfreak75 Restore it, Dont part it! FABO Gold Member

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            Honestly if I knew how to work my smartphone it probably would work I'm just not doing something right! This smart phone is alot smarter than me lol! I have a galaxy s7 iv had it for 21/2 years and still learning how to use it lol. I just learnt the other day I can text in pictures! So I used it to label the lines in my brake proportion valve so I can remember what goes where I just learned how to do it lol
             
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            • megavites

              megavites Well-Known Member

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              Here's the whiplash cam in my 318


              20170504_182350.jpg
               
            • Ottmundr

              Ottmundr 68 Fastback

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              My vote is for the lunati 10200702.
               
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              • nm9stheham

                nm9stheham Well-Known Member

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                Dang wyrm..... you just helped me out. I had never looked for a catalog download from Howard's.. I just looked at the online offerings. When you mentioned the (15) footnote, I was scratching my head over that, but FINALLY saw the catalog download. Looking in the SBM flat hydraulics cams, I saw the 15 footnoted cams.

                That makes it pretty clear about the .904 lifter cam lobes. Looking at a non-15 footnoted cam with intake duration of 269 and .050" duration of 215, lift is .455"... the normal standard stuff. Now looking at a 15 footnoted cam with intake 265 advertised duration. .050" duration is 218 but lift is way up to .502.... that is QUITE a difference. Even if the heads don't flow any more at .500 lift than at .450 lift, they still will get to peak flow faster and hold it longer. Better than a VooDoo or XE.

                It creates a new problem of how to accommodate all that lift in a simple build. Guess you back down to the 255 adv. duration one, and still get the same lift as the 262 VooDoo... same lift, maybe a tad less area under the curve so the top end is a few HP less but low end torque is up a bit. OK.... now the note for that 255 cam of "Best in 273-318" makes sense!

                I am pretty good at digging into details but I missed that one altogether up to now. Thanks for bludgeoning that into my wee brain.
                 
                Last edited: Oct 7, 2018
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                • Coronet 500

                  Coronet 500 Well-Known Member

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                  I used an Ed Performer intake, the triple primary boosters on the Street Demon give it great idle and sharp breakaway response which I liked, the large secondary gives whats needed on top.

                  I have found that 318 valve guide heights are not even from poor factory machining and anymore than .450" of lift should have retainer to guide clearance checked. To be sure I used a Comp Cam P/N 4726 tool to cut down top of guide and cut for positive locks, I used Comps recommended springs, retainers and locks as well. Mine was a fresh .030" over rebuild with stock cast pistons.

                  If I was doing the same engine for a car with stock converter I would use the XE 262 H. I have started to like the Howards products too.

                  http://www.compcams.com/catalog/COMP2012/pdf/COMP_Catalog_2012_362.pdf
                   
                  Last edited: Oct 7, 2018
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                  • toolmanmike

                    toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                    Good to know.
                     
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                    • nm9stheham

                      nm9stheham Well-Known Member

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                      Yes, I guess there IS something new under the sun... at least for me. Now to dig into the valve springs a bit more.
                       
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                      • dartfreak75

                        dartfreak75 Restore it, Dont part it! FABO Gold Member

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                        I'm looking at it now! Lol
                        Does that tool turn down the height of the guide or the outside of the guide?
                         
                      • nm9stheham

                        nm9stheham Well-Known Member

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                        Both for this tool.. the height for retainer clearance and the outside for the non-stock type of seal. If you don't want the different seals, I suppose you could just grind down the guide tops a bit with a grinder... not what you want to do 'on-engine' however! And there are several different tools available.

                        Spring seat cutters are different:
                        http://www.compcams.com/catalog/COMP2012/pdf/COMP_Catalog_2012_362.pdf

                        Got those heads off yet? Inquring minds want to know....
                         
                      • toolmanmike

                        toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                        The teflon seals are miles ahead of the umbrellas but do require machining the guides for them to work.
                         
                      • toolmanmike

                        toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                        I bookmarked this info. I would like to change up my 318 a bit too. There's many mild cams that work in stocker 318's just some work better. Thanks for the option. Comp isn't bad but a Mopar specific cam has got to be better.
                         
                      • AJ/FormS

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

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                        If I was doing an LA318, on the factory foundation; I would do everything I could to keep the Dcr up. And that means the ICA at final install needs to be very similar to what the factory ICA was; or else I would be prepared to also purchase a TC and gears.
                        When you look at a particular manufacturer's line of cams, you will generally see them on a 110 LSA, and therefore see, a steady march of the ICA changing about 3.5 degrees per cam size. When you install those cams at split overlap, you will generally see the cylinder pressure drop about 4 psi per size, and along with it, the same in VP.
                        The factory LA318,starting at 7.8Scr and at 800 ft, with only a cam change;
                        with a 240/248/112 cam, ...makes about 130/107VP factory cam
                        With a 240/248/110 cam, it makes about 131/109VP
                        With a 248/256/110 cam......................~127/103VP
                        With a 256/262/110 cam..................... ~123 /97VP
                        With a 262/268/110 cam..................... ~120/ 93VP
                        backing up
                        With a 256/262/108 cam......................~125/100VP
                        With a 262/268/106 cam...................... ~124/99VP

                        Pay particular attention to the VP, 5 out of 6 cams will lose bottom end grunt.So, IMO, all these guys are gonna need a TC and gears else the cam will be a disappointment.
                        Now lets pump the compression up and try that again
                        With a 240/248/112, factory cam at 9.1Scr ~159/131VP factory cam
                        With a 262/268/110 cam, at 9.5Scr...................~156/120VP
                        With a 268/276/108 cam, at 9.5Scr..................~ 155/118VP
                        Notice the VP, which tells you you can keep the factory TC and gears at least for a while, cuz the new VPs are far superior to the factory 107 number.

                        So ask yourself; what's a set of pistons worth,installed, to get the Scr up, and nothing else......
                        versus
                        leaving the Scr at 7.8, installing that big cam, and the bigger TC, and rear gears....... just to have the same or similar low-rpm performance..... allbeit a peppier top-end, which you might experience just once, on the way to 65 mph.
                        That's the rub.
                        Each of these cams will move the rpm of peak power up, about 200 rpm starting with the factory one at about 4000, and the 268 at maybe 5200, not likely with factory heads but let's just say. And lets add 400rpm to get a preliminary shift rpm, but keep the trap to peak power plus 100rpm
                        Ok so with 2.76 gears 4400 is~ 49mph, and 65 in second gets you ~3500
                        And with 3.23 gears,4400 is~42mph,and 65 in second is..... ~ 4100
                        And the go-to 3.55s,. 4400 is~ 37mph, and 65 in second gets you ~4500
                        But choose 3.91s,...... 4400 is~ 34mph, and 65~4900 if you are brave
                        So here you can see that the perfect gear to hit 65 at ~4100 would be 3.23s
                        >>But lets jump to the 262 cam which might peak at 5000 and might like to trap at 65=5100 in second. Now the best gear is 4.10s. Ok sure you can run less gear, say the 3.55s again, and trap 65~4500, fully 600 rpm short of peak. Now if you were still at 7.8 dcr, you would be some ways down on power, and there is a good chance the 9.1 factory-cammed engine, with 3.23s would fly by you, or at least give you a good run. Sometimes less cam is quicker ET. And if you now threw some TC at the 9.1factory cam combo, well then let the SHTFan.

                        But now, what about a solid lifter custom cam, with a fast rate of lift designed for a .904 lifter. Say a 252/258/106, that after lashing might be 248/254/106, and actually slams the intake shut at 48* ICA, and still at 7.8Scr, this will get you 131psi/109VP. Where have we seen that before, oh, yeah, at the top of the list,with the factory cam! So now you lose nothing on the bottom, compared to the stocker, but have moved the peak power up possibly 200 rpm, and the lift on that cam is gonna add it's shot of power and the 106LSA is gonna double your overlap, so the headers are gonna pump a few more horsepower into the mix. This is the way to exploit your LA318 low-compression engine.
                        Ok one more, lets do the 268/276/106solid cam, with an after lash of 262/268/106 and lets put it in the 9.5 Scr engine.
                        I get 161psi/128VP.
                        This is way more low-rpm performance than the stocker (130/107),and is a really good trade. Plenty more than stock performance with a power peak up about 800 rpm higher, and tons of pressure to rocket the teener at every rpm.
                         
                        Last edited: Oct 7, 2018
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                        • nm9stheham

                          nm9stheham Well-Known Member

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                          Hey, thank Wyrnrider for hammering on this. I've read a lot of contention on this matter and assertions that it does not matter; I've tried to keep an open mind. It's like so many things in motor-heading.... in some applications it may not matter; in others, it will. This looks (to me) a like a case where it will matter.

                          This is quite a bit different from the old low lift, slow ramp cams. It goes past the limits of what I thought was reasonably possible with flat tappets. Now, I AM conscious of what it may mean for valve speeds and the need for better valve springs...hence the need to look at the recommended springs and see if they are just 'normal' hi-po springs, like the stock 340 springs, or something more.

                          Edit to add: Howards recommend spring (98438) has a rate of 425 lbs/in which is a step higher than 340 springs or Comp 901's. They are duals rather than single with damper. So this may indicate some faster acceleration rates... no wait, Howards lists that for ALL their SBM hyd flat tappet cams regardless of ramp rate, so that is not it. For 302 heads like the OP has, and a smaller cam and the more limited upper RPM range of the 2, I suspect 340 or Comp 901 springs would be OK; I'd certainly try it out.
                           
                          Last edited: Oct 8, 2018
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                          • dartfreak75

                            dartfreak75 Restore it, Dont part it! FABO Gold Member

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                            No not yet still working soon as I get a day off I'm going to. I will let you know
                             
                          • toolmanmike

                            toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                            Isky does that with their E-4. A pretty mild cam and dual springs are recommended.
                             
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