Need to do some adjustments with 426 Hemi.

1968 -1970 Mopars

  1. sixpakrob

    sixpakrob Well-Known Member

    Messages:
    79
    Likes Received:
    43
    Joined:
    May 17, 2013
    Location:
    Yukon, Oklahoma
    Local Time:
    4:02 AM
    I have a 1968 Super Bee 426 Hemi car. Is was set up as a strip drag car, hot cam with a shift kit in trans, 410 dana with super comp springs.

    It came originally with 8 3/4 323 posi, and I am wanting to convert back.

    What cam and lifter set do I need? I am looking for a nice rear end, gears, springs. I want original stuff. Robert

    IMG_4146 copyEDIT2 copy 2.jpg
     
    • Like Like x 4
    • Dominic

      Dominic Well-Known Member

      Messages:
      45
      Likes Received:
      24
      Joined:
      Sep 27, 2018
      Location:
      San Diego
      Local Time:
      2:02 AM
      Are you willing to trade the Dana 60? I have a great 8 3/4 w/ 3.23 suregrip setup in my Hemi car. Could maybe make a deal if you're interested.
       
    • sixpakrob

      sixpakrob Well-Known Member

      Messages:
      79
      Likes Received:
      43
      Joined:
      May 17, 2013
      Location:
      Yukon, Oklahoma
      Local Time:
      4:02 AM
      Well, the dana is worth more money for sure. What year is the car, what case it is?, I want springs too, it has new brakes and wheel kits, etc... where are you in the world? I am in Oklahoma
       
    • Dominic

      Dominic Well-Known Member

      Messages:
      45
      Likes Received:
      24
      Joined:
      Sep 27, 2018
      Location:
      San Diego
      Local Time:
      2:02 AM
      Yep of course, trade + cash for the rear ends- out of a 1969 RR, 489 case 29 splines.
      I have original XHD springs out of a 68 RR as well... but well worn quality. Located in San Diego, CA
       
    • sixpakrob

      sixpakrob Well-Known Member

      Messages:
      79
      Likes Received:
      43
      Joined:
      May 17, 2013
      Location:
      Yukon, Oklahoma
      Local Time:
      4:02 AM
      The correct case would be 742, not sure about the springs... or best to do this.
       
    • Dominic

      Dominic Well-Known Member

      Messages:
      45
      Likes Received:
      24
      Joined:
      Sep 27, 2018
      Location:
      San Diego
      Local Time:
      2:02 AM
      Ahh gotcha... I would probably be interested in buying the Dana when you find a 742, though. Shoot me a pm if you want to sell it
       
    • moparedtn

      moparedtn Ed on the Ridge FBBO Gold Member

      Messages:
      6,521
      Likes Received:
      9560
      Joined:
      May 14, 2011
      Location:
      On the Ridge, TN
      Local Time:
      5:02 AM
      sure grip.jpg
       
      • Like Like x 6
      • Thanks! Thanks! x 1
      • Wietse

        Wietse Well-Known Member

        Messages:
        1,292
        Likes Received:
        479
        Joined:
        Apr 16, 2017
        Location:
        Netherlands
        Local Time:
        11:02 AM
        I would first see what static compression ratio you are at now.
        With the cam specs of the current camshaft you can estimate the dynamic pressure as well.
        Because likely you are running a high compression now, throwing in a milder cam will just increase cylinder pressures beyond where you want it to be.
        Once you got those numbers you can maybe find a cam to make it work with decent cranking pressures.
        Once you got the cam you can see what convertor and rear gears you can run.
         
        Last edited: May 3, 2020
      • sixpakrob

        sixpakrob Well-Known Member

        Messages:
        79
        Likes Received:
        43
        Joined:
        May 17, 2013
        Location:
        Yukon, Oklahoma
        Local Time:
        4:02 AM
        Okay, how does it find what the compression is? Thank you. robert
         
      • Wietse

        Wietse Well-Known Member

        Messages:
        1,292
        Likes Received:
        479
        Joined:
        Apr 16, 2017
        Location:
        Netherlands
        Local Time:
        11:02 AM
        Do you have the details of the engine build, camshaft, pistons (manufacturer/type/oversize), cylinder heads (stock or Aluminium),head gasket tickness, etc?
        Or did a PO do this?
         
      • sixpakrob

        sixpakrob Well-Known Member

        Messages:
        79
        Likes Received:
        43
        Joined:
        May 17, 2013
        Location:
        Yukon, Oklahoma
        Local Time:
        4:02 AM
        I know nothing of the cam, compression etc...
         
      • Wietse

        Wietse Well-Known Member

        Messages:
        1,292
        Likes Received:
        479
        Joined:
        Apr 16, 2017
        Location:
        Netherlands
        Local Time:
        11:02 AM
        In that case it's best to pull the cylinder heads, camshaft, etc. and see what you have first before ordering a new camshaft.
        You might find the piston part number, can measure cylinder head volume and do some math from there on on what fits your application with or without new pistons.
        Something that would give some indication is a compression test on all 8 cylinders to see what your current cranking pressure is.
         
      • sixpakrob

        sixpakrob Well-Known Member

        Messages:
        79
        Likes Received:
        43
        Joined:
        May 17, 2013
        Location:
        Yukon, Oklahoma
        Local Time:
        4:02 AM
        I did test the pressure in the cylinder and it was 150 pounds. I am not sure what that means.
         
      • Wietse

        Wietse Well-Known Member

        Messages:
        1,292
        Likes Received:
        479
        Joined:
        Apr 16, 2017
        Location:
        Netherlands
        Local Time:
        11:02 AM
        150 psi is a number to stay close to.
        Did you check all 8 cylinders? If they are all close to each other it means your bottom end is still good and does not require any attention.

        I have no idea what a hemi has on combustion chamber volume and i am unexperienced in doing the math myself.
        Hopefully one of the guys who know this will chime in and help out.
        But with the cranking pressure you can work backward and estimate a static compression ratio.
        If you are able to find any camshaft specs you can also estimate the dynamic ratio.
        Once you know these numbers you can reuse them to calculate the static and dynamic compression ratio's and the cranking pressure when using a different camshaft.
        To be accurate you need to know the piston make/model, combustion chamber volume, camshaft make/model and head gasket thickness.
        That's why i said that it is the best to dismantle the engine partially so you can check for part numbers on piston and camshaft, measure the bore and head gasket thickness so you know what you are working with.
        On my camshaft the part number was engraved on the cam sprocket flange, i know a lot of pistons will have a reference number stamped in the top.

        I have been doing a similar job as you want to do as my 440 was setup for a racer with 185 psi cranking pressure and it has been quite a job to bring that pressure down and make the car more streetable.
        Instead of replacing the camshaft i had retarded it as i had the option to do so and my cranking pressure was so stupidly high, this delays the closing point of the intake valve on the compression stroke, which in effect reduces dynamic compression ratio and cranking pressure and makes it more a streetcar instead of racer.
         
      • Wietse

        Wietse Well-Known Member

        Messages:
        1,292
        Likes Received:
        479
        Joined:
        Apr 16, 2017
        Location:
        Netherlands
        Local Time:
        11:02 AM
        Do you know the engine has a stroker kit or is bored oversize?
        And what is your elevation above sea level?

        Because according me, (bear in mind in am just a beginner with this) with a stock bore and stroke and a bigger then stock cam i end up with below to get a 150 psi cranking pressure on the gauge.
        Assuming when at sea level.

        Static compression ratio: 9,5:1
        Dynamic compression ratio: 7,5:1

        This is with a camshaft with a 245-250* duration @ .050"
         
      • sixpakrob

        sixpakrob Well-Known Member

        Messages:
        79
        Likes Received:
        43
        Joined:
        May 17, 2013
        Location:
        Yukon, Oklahoma
        Local Time:
        4:02 AM
        I am presuming it is standard bore since the car only has 22,000 miles on it. It is not stroked but they did balance the motor.
         
      • Cranky

        Cranky Banned Staff Member FBBO Gold Member

        Messages:
        20,735
        Likes Received:
        17182
        Joined:
        Dec 4, 2009
        Location:
        Pasa-getdown-dena Texas
        Local Time:
        4:02 AM
        I don't know of any 8 3/4 rears that came with 29 spline axles.....at least not in the 60's-70's.

        Also, this is basically a wanted ad with a tech question. For the OP, if you want to get a better response, insert a wanted ad specifically for the rear end in the 'wanted section' then ask your tech question in a separate thread. Thanks.
         
      • pearljam724

        pearljam724 Well-Known Member

        Messages:
        1,209
        Likes Received:
        500
        Joined:
        Oct 14, 2018
        Location:
        U.S.
        Local Time:
        5:02 AM
        Some guys live the life. Here, I’m wishing to gain compression and some guys are willing to pay to give it away. Ha ha !
         
      • moparchris

        moparchris Well-Known Member

        Messages:
        176
        Likes Received:
        107
        Joined:
        Jul 19, 2008
        Location:
        az
        Local Time:
        3:02 AM
        Just my two cents but I've had many hemi cars over the years and have maybe learned a thing or two.
        First thing is what do you really want out of this car? Do you want a "stock" hemi car. Next would be "why"? Here's where I'm going with this.
        I have had two automatic hemi b-bodies (67 Charger, 68 Charger R/T) 3:23 gears, stock motors. I hate to break the bubble but they are pretty much dogs in this combination. They are nice to drive and easy, blah, blah, blah but when you stomp on the loud pedal all they do is make noise. You are not accelerating very hard. Hemi's have huge port volumes, large plenum volume and it takes a lot of RPM's to make things happen. Is this what you want? If you are interested in driving it calmly around town or going to a show to win a trophy fine.. by all means do it. If you are somewhat juvenile, yes that includes me, you may not be happy with this set up.
        This then leads to other questions. Would you be happier with a "stock" motor but with more gear in the rear. 3"91 or 4"10's would make a huge difference in performance.
        Originally this car had solid lifters. Does it still? Is this what you want to keep if it does? Do you want it have hydraulic lifters? Each style of camshaft requires a unique set of push rods. Are you able/willing to measure the lengths that you will need if you are making a change. From my experience, buying the Mopar Performance pushrods is not very effective. It is best to measure your actual engine and determine what exact lengths you need for intakes and exhausts. This will play into what is available to you and what will work best with gearing etc..My two cents. why would you want hydraulics if you can run solids. Solids rev so much more freely and they do not require constant maintenance. Unless you run high spring pressures and run it hard you do not need to be constantly taking the valve covers off and setting valves.
        Someone above had asked about the pistons and compression. Knowing this is critical to making the engine respond in the manner you will want. You need to know this information in order to ascertain the correct camshaft profile. For your info 150 psi cylinder pressure is a little low IMO. Most of my hemi's in stock configuration have been in the 185 +_ 5psi. Did you measure all cylinders? Did you have the throttle bores open when you did this? You're compression may be o.k. but if you have a larger cam with a lot of duration you could be effectively lowering your compression ratio some.
        In the end this is your car. Do as you please. But take the time to go through this in a methodical manner and don't take short cuts. If you don't know how to ascertain some information, ask. Lots of people will want to help.
        Take this for what it's worth but if you ever want to p.m. me feel free. I'd be happy to talk to you about this if you want.
         
        • Like Like x 1
        1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
          By continuing to use this site, you are consenting to our use of cookies.