Cam advice or input

Discussion in 'Big Block A body Tech' started by burkjosw, Sep 16, 2018.

  1. burkjosw

    burkjosw Member

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    Hello all I'm building a 68 383 to use in my 68 barracuda so far it's a 40 over 68 383 block Edelbrock RPM 75cc heads with Keith Black pistons, Edelbrock TM6 intake, plan to use headers but I haven't purchased any yet I have a new Mopar 484 cam and lifter set I was going to use but I may just save that and buy another for this engine, maybe something from Hughes? Will be running manual disc brakes on the front and a 4-speed, haven't settled on rearend gearing just yet but I do plan to drive this car a lot, any cam recommendations would be appreciated
     
  2. AJ/FormS

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

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    At 740ft above sealevel, and aluminum heads, you have the potential to build a screamer. But you are gonna have to co-ordinate very carefully, your Static compression ratio and the cam's Intake Closing Point..... to achieve the end result.
    And for a streeter, horsepower usually takes a back seat to driveability.
    The 4-speed indicates that you can use a tight LSA cam, and the TBA rear gear is a bit of a stumbling block. I have heard that Oklahoma is large and flat and the cities are spread out,lol. Does that mean you, like me, are miles from nowhere and spend a lot of time on the hiway, getting to somewhere? And what tire-size are you planning to run?

    The point is that if you put a 6000 rpm cam in there, you need a matching rear gear, but cruising with 4.30s ain't the most fun thing to do. And 24.5" tires are pretty small, compared to 28s which are about the tallest that will fit in the stock tubs.While the difference in tires is about 14.5%, this is worth between 1 and 2 gear sizes.
    So before you chose a cam, you kindof need to nail down the useage; how important is hiway cruising to you?

    I like to gear my manual trans combo to be at or near the power-peak at 60 mph at the top of second gear, so I get max performance in two gears, without having to shift into third.
    The formula is;
    mph= (rpmxTc)/(1056xR1xR2)................. where Tc is Tire circumference, 1056 is a conversion factor, and the Rs are your gears. Rearranging and plugging in the known numbers, we get;
    Rpm =(60x1056 x 1.92second gearx R2)/Tc; and I'll use 27" or 85"TC
    And that simplifies to; rpm/R2=1431, rearranged to 1431 x R2 =rpm....
    And so the power peaks would be
    1431x3.23=4620
    1431x3.55=5100
    1431x3.73=5340
    1431x3.91=5600
    1431x4.10=5870
    1431x4.30=6150
    That's what I like to do.
    Now here's how this works;
    Example #1
    Say you put that 284/484 in there and say the power-peak is at 5400. But say you run it on 3.23s; so the rpm at 60mph is 4620. You had to outshift first at about 5700 or 53mph, coming into second at 4110. So your monster 383 has to pull second from 4110 to 4620. Ima thinking it's gonna be struggling, with TM(TorqueMultiplication ) of 6.20.
    Example #2
    Say you put the same engine together, but run it with 4.30s.So that at 60mph the rpm now would be 6150. sounds good right? But your power peak was at 5400, and the shift point shoulddabin at about 5700. So she is 450rpm past the shift point and already way down on the power curve. You shouldda shifted at 5700/55 mph and third would have struggled again, from 55 to 60mph and from 4150 to 4490, but now with TM of just 6.02. Wait where have we seen that before? Oh yeah, in example #1.
    Example #3
    Ok so lets put the proper gear on it, of 3.73s
    Now you are gonna run first up to 5700@46mph, and shift into second. The incoming rpm will be 4110, and ending at 60=5340. Oh lookitthat we could advance that cam a bit or go to the next gear. And the second gear-TM is now 7.16; whoa! that's 19.4% better than either of the other two; and it began at 46mph, so that monster 383 will be blasting thru there faster than either of the other two combos!
    Ok so say you like these numbers, and decide that the 3.73s are what you want. Are you OK with 65=3010rpm?
    If yes, then you have to figure out what compression ratio to run with this 284/484 cam,and those 75cc aluminum heads.
    And with an ICA of 66*,I get over 11/1. Ima thinking 11.3 actually. And that would take a total chamber volume of 76.28cc. Next question is; how expensive is it gonna be to achieve that.And what's gonna happen if all you can achieve is 85cc? Well 85 would get you just 10.24Scr, and might make just 160psi, and below 3000rpm is gonna feel like maybe a 340. And let's not forget that you can run iron heads at 160,and pump-gas; so you have given up the prime reason for using the aluminum heads, their ability to swallow copious amounts of pressure with out detonating.
    But now, if you spent the money to achieve the 11.3Scr, you would be rewarded with so much low-rpm torque, that your car is gonna spin the street-tires all the way to 60mph anyway, and so who cares what gears are back there,lol.

    Now go back to the formula, pick a different power-peak
    and work it out with a smaller cam, or a cam with an earlier closing intake
     
    Last edited: Sep 16, 2018
  3. burkjosw

    burkjosw Member

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    If I did it right the compression comes out to around 9.5 :1 with kb pistons with 5cc valve relief but I may be wrong there, I'd like to see something around the 10:1 area
     
  4. krazykuda

    krazykuda FABO Gold Member FABO Gold Member Technical Editor

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    I would use the 484 cam... I had one in a small block and it ran great...

    Plus you already have it...
     
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    • burkjosw

      burkjosw Member

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      Have been looking at Hughes cam part number seh4246bl-8 probably give them a call soon and see what they would recommend
       
    • krazykuda

      krazykuda FABO Gold Member FABO Gold Member Technical Editor

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      I had bad experience with Hughes... Don't like the way that they run their business... :BangHead: :mad:
       
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      • burkjosw

        burkjosw Member

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        Wow now that's a lot to think about, thank you for the input
         
      • famous bob

        famous bob mopar misfit

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        On the contrary, I`ve had nothing but good experience w/ Dave at hughs engines. And another employee also(don't remember his name), they have done everything a guy could expect.
        Their shipping charges have always been too hi, is the only gripe I got -----but everybodies is now !
         
      • AJ/FormS

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

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        I've have not done much business with Hughes, but I have had good success with products that I have purchased.
        Altho, IMO, they recommended too big a cam for me on the last go-round. I opted for a cam two sizes smaller than their recommendation, and have never been sorry. Never once have I thought " gee, I shouldda got the bigger cam", lol.
        I got their 230@.050, which is now discontinued, and the specs are published as 276/286/110. It's almost perfect for me.
        Well, it couldda had more lope,lol............... I was expecting more lope.... where's the daymn lope! After the first few WOT pulls, I didn't care anymore about the daymn missing lope.
         
      • gdbuick

        gdbuick Well-Known Member

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        Interested in how you make out with this build please keep
        us updated. Sounds very similar to what I would like to do for my 68 383 auto dart with manual disc brakes this winter. Planning on alum heads and the option to convert to a tremec 5/6 speed manual so I can drive on highway. I do want a lumpy cam.
         
      • dartgarth

        dartgarth Well-Known Member

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        Which KB piston is it? Are you looking for a Hydraulic cam or something more exotic? Do you want lope or smooth? Do you have a HP number or ET goal? As AJ has pointed out tire size and gear ratio will play a large part. Your heads and intake will support a large cam which will need some compression for optimum performance.

        If you are going to buy a cam I like to suggest a custom grind, then you can get exactly what you want and it really doesn't cost much more. If you want to save a few $$ run the MP cam, it's a good grind even if it's a bit old school ( I do think they made two versions though one on 114 degrees separation and one on 108 so check which one it is).

        Garth
         
      • burkjosw

        burkjosw Member

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        K
        Kb240 I believe was the part number , i bought them almost 10 years ago, I have come to the conclusion that they are not going to get me to the compression ratio I want, I'd like to reach 10.5 or 11 to 1 , not going to be a race car by any means just a really fun driver, I'm considering decking the block and or buying some domed pistons for it, just want to make sure what i end up buying works well together I don't mind buying new stuff and saving what I have for another project, I like the lope , around 450hp shouldnot be to hard to get
         
      • RustyRatRod

        RustyRatRod Just another dumbass. Technical Editor

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        • dartgarth

          dartgarth Well-Known Member

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          Solid grind Rusty, I had the H272 (one size smaller) cam in a basically stock 383 with a Torker intake, Holley 750 and headers and it ran really well.

          Garth
           
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          • RustyRatRod

            RustyRatRod Just another dumbass. Technical Editor

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            Dick and Robert Landy built a stock bore and stroke Chrysler 400 for one of the magazines back in the late 80s with that cam I linked to above. With stock replacement pistons and "whatever else" they did, it made over 1 HP per cube. It was pretty impressive. But with the 383, it has the potential for more, since its compression can be higher.
             
            Last edited: Sep 21, 2018 at 8:12 PM
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            • dartgarth

              dartgarth Well-Known Member

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              If those pistons are domed, rather than dished ( that's how I read the specs) you should end up with about 10.69 with a .027 cometic head gasket and a true 0 deck. you could deck more or machine the heads if you need more compression. Pistons would be down the hole .024 so quench would be .051. If you decked .010 for .041 quench you would be at 11:1. Hopefully my math is right on all this.... You would really need to measure everything including P-V clearance and verify quench.

              You definitely need a healthy cam for that compression at least 230 degrees @ .050 straight up. Personally I would get a custom cam at that point, that would be optimal.

              My 383 is a true 9:1 (custom JE pistons), 906 heads (unported but good valve grind with Ferrea valves) 1.6 iron rockers, performer RPM intake, TTI headers and a small custom roller by Mike Jones, 217, 225 @ .050 with .340 lift 109 lobe separation in at 2 degrees advanced. Idles with 17" vacuum and makes 400 HP @ 5200 and 436 Ft/LBS @ 4300 with over 400 ft/lbs from 3000-5100. This is on a conservative dyno.

              Garth
               
            • Sweet5ltr

              Sweet5ltr Well-Known Member

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              Well, I'll put this out their. Asymmetrical camshaft lobe designs, really look into some of the past research done by Harold Brookshire (UltraDyne -current Bullet Cams-, Comp Cams, Lunati Voodoo series). The Asymmetrical lobes in common-terms, allows the valve to be seated more gently than it was opened. This is what you're looking for in a street engine. I'm not going to recommend a camshaft (my version of street may be very different), but in my opinion, take advantage of the airflow of those cylinder heads. You're getting very little out of them with a .480" lift camshaft.

              An older post from Harold;
              Symmetrical vs assymmetrical(or unsymmetrical) lobe designs......
              I think the last symmetrical lobe designs I did were in 1976...... Many of them are still being sold today, and they work OK(not BEST, or I would still be designing them...).Assymmetric cam design merely means that the opening and closing sides are designed differently. You can open fast, shut slow, or you can open slow, shut fast.
              I got my inspiration for unsymmetric cams from Racer Brown, who didn't do them,AFAIK. He wrote an article in the mid-60s about Toyota engines, in which he noted that cams that opened and shut the valve very fast made great power, but were brutal on parts. He also noted that cams that opened and shut the valve much slower were very stable in high RPM and didn't break parts, althought their low-end power was down.
              I quickly identified shutting the valve hard and fast with breaking parts, and shutting the valve slower with less parts breakage and better high-RPM stability. Tying fast openings and slow closings seemed to me to be the best of both worlds, but it was at least 10 more years before I designed and made my 1st unsymmetrical cam lobe. This cam was the Comp Cams 324-4(I believe, I don't have a CC catalog available..), 324° at .020, 286° at .050, .4544 lobe lift---They still sell that lobe today. It turned 11,000 with ease back in 1977-1978.
              My 1st unsymmetric hydraulic was the 268 High Energy cam, 268° at .006", 218° at .050", and .454" valve lift.
              What I have said since 1977 is that by delaying the opening of the intake port, reversion(exhaust gas being pumped out by the rising piston on the exhaust stroke) is minimized, compared to a cam with an earlier opening. Because this reversion is minimized, when the piston starts down on the intake stroke, the lessened reversion cleans out of the intake portearlier, and starts airflow earlier. Would YOU let your opponent in a drag race have a .1th head start? What about a .25th?
              Although I use very fat cams at high lift, this isn't actually a part of unsmmetrical cams. But because the properly-done unsymmetric cam has a higher port velocity, a fatter-duration cam in high lift area has MORE time to fill the cyclinder, and is filling it at a FASTER rate.
              Shutting the valve gentler helps ensure aginst valve bounce, and the corresponding release of cylinder pressure back into the intake runner. It also helps parts life.....
              I will try to answer more tomorrow/today. I have only Saturday and Sunday every week at home, The last 5 weeks have been spent in Bowling Green at Corporate HQS, learning how to fill out forms like a proper engineer.
              There are also gains to be had with unsymmetric cams as exhaust lobes, and the two, intake and exhaust, work together very well.
              I will see you all tomorrow....
               
              Last edited: Sep 21, 2018 at 1:08 PM
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              • Coronet 500

                Coronet 500 Well-Known Member

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              • Bighead440

                Bighead440 Well-Known Member

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                That ^^ is my go-to cam for a stock 383HP B-body with an automatic and 3.23 gears. Really too small for a 440, IMO, but perfect for the short stroke daily-driver 383 auto (11" converter) with a freeway gear. With a light A-body and a 4 speed, and more importantly in a 383, VALVE RELIEFS, I would go to a larger camshaft with tighter lobe separation angle. A 275DEH Comp is pretty versatile, but I like it with iron exhaust manifolds in a B-block. Maybe the XE275HL from Comp would be better suited if you don't mind adjustable valvetrain, minimum lifter preload and some noise from the aggressive lobes. If it were a 440, I'd rather see the XE285HL, but a 383 you have to be a little more conservative.
                 
              • Bighead440

                Bighead440 Well-Known Member

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                Good call Rob, plenty of vacuum, durability and cruiseability. If he wants a little less vacuum-lol-and a few more RPM, the old "Commander" 302/312, 232/242, .504/.528", 112LSA would still be streetable and fit well with the piston reliefs he has. I have run this grind in two BB's with non adjustable valvetrain and single (Comp 911) springs with great success. It's a long-lasting lobe design with less stress on seats and springs (and ears) than these aggressive cams everybody recommends for all applications these days, like they're getting a commission. LOL
                 
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                • burkjosw

                  burkjosw Member

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                  Not to worried about vacuum as it won't have power brakes. Or power anything for that matter manual steering non ac car, I really do appreciate all the input it's given me a lot to look into and made me think about things I've overlooked
                   
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                  • dartgarth

                    dartgarth Well-Known Member

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                    Honestly, I'd get all your info together and then fill out some cam recommendation cards. The more info you have the better and be super honest with your goals and requirements. This will give you an idea of what will work with your particular combo. I filled out for Comp, Lunatti, Crane and Jones and Howards. Comp came back with a recommendation that wasn't even close to what I was requesting ( I wanted good idle vacuum), Crane got back to me with a fairly conservative cam. Howards didn't get back to me. Mike Jones from Jones Cams got back to me with what thought was the best grind for me and IMO the cam works very well. About Us | Jones Cams Look him up, he is pretty well regarded. Communication was good, but not lightning fast. It took a total of 8 weeks to get the cam from ordering it to my doorstep in Canada. (apparently he was pretty backed up in the shop as this was the spring)

                    Garth
                     
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                    • famous bob

                      famous bob mopar misfit

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                      YEAH, THERE IS ONE OF THE OWNERS THAT IS TOO BUSINESS LIKE, BUT DAVE AND ANOTHER GUY HAVE BEEN PRETTY GOOD TO ME !! No problems w/ their business, shipping being too hi , is the only bitch !!
                       
                    • fishmens67

                      fishmens67 Well-Known Member

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                      the other guy is probably Tim. Tim is very knowledgeable .
                       
                    • Vamisk

                      Vamisk Well-Known Member

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                      Not trying to hijack the thread I'm just curious how big of an impact cam profile has on MPG (think 455 Olds vs 455 Pontiac)?