Cam Specs for 69 & 70 - NCRS Discussion Boards

Cam Specs for 69 & 70

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  • Pamela H.
    Expired
    • August 8, 2012
    • 68

    Cam Specs for 69 & 70

    What were the specs on the 427/390 hp cam for '69


    What were the cam specs for the 1970 454 high horsepower with hydrolic ?

    Thanks a bunch!
  • William C.
    NCRS Past President
    • May 31, 1975
    • 6037

    #2
    Re: Cam Specs for 69 & 70

    All the hydraulic lifter cams for "454" in '70 carried the same cam with lift of .2714 on the intake lobe and .2824 on the exhaust. Lobe lift, multiply by rocker ratio to get valve lift. I think a big-block is 1.65 to 1 rocker ratio. Cam was used for many years on 396-402-427 applications. Sorry I don't have the duraton.
    Bill Clupper #618

    Comment

    • David H.
      Extremely Frequent Poster
      • June 30, 2001
      • 1523

      #3
      Re: Cam Specs for 69 & 70

      Originally posted by Pamela H Haus (55255)
      What were the specs on the 427/390 hp cam for '69


      What were the cam specs for the 1970 454 high horsepower with hydrolic ?

      Thanks a bunch!
      The link below is to the GM Heritage Center. You can download a pdf covering dealer and Manufacturer Association information about most Corvettes. You might look through the entire pdf for interesting info, but the camshaft information is on pdf pages 132 and 148 for 1969, and pages 98 and 137 for 1970.

      GM Heritage is committed to preserving the rich history of General Motors brands while providing a foundation for continued innovation into the future.


      Click on the link: The page with "Vehicle Information Kits" opens up.

      Scroll down the page to Corvette and click on "Show": A list of Corvette years from 1953 through 2006 opens up.

      Select (click on) the year of interest (in your case 1969 or 1970): A usage agreement pops-up.

      Accept the usage agreement: A informational pdf will download.

      Save the pdf off to your computer. The camshaft information is on the above noted pages.

      Note: this is what GM published prior to production - what they DID during production may be different - it is a place to start.

      Lots of other interesting information in the pdf, worth a look through.
      Judging Chairman Mid-Way USA (Kansas) Chapter

      Comment

      • Pamela H.
        Expired
        • August 8, 2012
        • 68

        #4
        Re: Cam Specs for 69 & 70

        GREAT, I appreciate it!

        Comment

        • Duke W.
          Beyond Control Poster
          • January 1, 1993
          • 15662

          #5
          Re: Cam Specs for 69 & 70

          The AMA specs quote gross duration, which is not directly comparable to most other camshafts. Most aftermarket cam manufacturers quote duration at .050" lifter rise and/or SAE J604 duration, which is .006" valve lift.

          The .050" lifter rise duration for the Corvette big block hydraulic camshaft that was used from '66 to '73 is 214/218 degrees. The inlet POML is 110 deg. ATDC, and the LSA is 115 deg.

          This is an excellent camshaft that yields a very torquey engine with good top end power.

          More top end power and additional usable revs can be had without affecting appearance or low end torque by massaging the heads and retarding the cam four degrees, especially on a 454, and post '70 low compression big blocks that were designed for low octane unleaded fuel should have the compression ratio raised to about 10:1, which is compatible with current unleaded premium fuels and will improve fuel economy, across the range torque, and top end power by 5-10 percent.

          The "specified" big block rocker ratio is 1.7:1, but as with the small block rocker arms, it is not constant. It starts out below this value and may not actually achieve 1.7 at maximum lift. Small block data yields a lash point ratio of about 1.37:1 and about 1.44:1 maxium lift with about a 0.3" lobe versus the "spec" of 1.5:1.

          I have never obtained a reliable data set to characterize actual big block rocker ratio behavior.

          Duke

          Comment

          • Clem Z.
            Expired
            • January 1, 2006
            • 9427

            #6
            Re: Cam Specs for 69 & 70

            38833986 camsshaft, dur@.050 214/218,lobe sep. 115,open/close @.050, (-3) 37 int, 49 (-11) exh., lift .461/.480

            Comment

            • Pamela H.
              Expired
              • August 8, 2012
              • 68

              #7
              Re: Cam Specs for 69 & 70

              ? What's the easiest way to bump up the compression by 1.5-2.0?

              ? 69 427 435 hp hyd. lifters or solid?

              Comment

              • Patrick H.
                Beyond Control Poster
                • December 1, 1989
                • 11643

                #8
                Re: Cam Specs for 69 & 70

                Originally posted by Pamela H Haus (55255)
                ? What's the easiest way to bump up the compression by 1.5-2.0?

                ? 69 427 435 hp hyd. lifters or solid?
                How about a better question - what is your goal for the motor?
                Vice-Chairman (West), Michigan Chapter NCRS
                71 "deer modified" coupe
                72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
                2008 coupe
                Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.

                Comment

                • William C.
                  NCRS Past President
                  • May 31, 1975
                  • 6037

                  #9
                  Re: Cam Specs for 69 & 70

                  No real easy way to bump compression by that much, new pistons is about the only method. 427/435 mechanical lifter (solid)
                  Bill Clupper #618

                  Comment

                  • Duke W.
                    Beyond Control Poster
                    • January 1, 1993
                    • 15662

                    #10
                    Re: Cam Specs for 69 & 70

                    Originally posted by Patrick Hulst (16386)
                    How about a better question - what is your goal for the motor?
                    Ditto what Patrick said. I sense that some "engine builder" is leading you down the primrose path. This oil pump shenanigan should give you a clue. Tell us, in detail, what you are trying to accomplish. What is your objective?

                    You are a new NCRS member. There are guys on the TDB that worked for GM in the era - engine system engineers, production engineers, plus a whole bunch who are experienced in configuring both road engines and race engines.

                    Make no mistake, they are two very different animals.

                    Duke

                    Comment

                    • William C.
                      NCRS Past President
                      • May 31, 1975
                      • 6037

                      #11
                      Re: Cam Specs for 69 & 70

                      I'm with Patrick and Duke!
                      Bill Clupper #618

                      Comment

                      • Richard M.
                        Expired
                        • April 1, 1993
                        • 198

                        #12
                        Re: Cam Specs for 69 & 70

                        Pamela,
                        You have a PM from me.

                        Best Regards,

                        Richard Mynatt

                        Comment

                        • Pamela H.
                          Expired
                          • August 8, 2012
                          • 68

                          #13
                          Re: Cam Specs for 69 & 70

                          I just responded in detail and lost my connection, and lost the post! ARRRRGGGGGHHHHH
                          Briefly...I am but my brother who is in this rebuild with me has been working on Corvettes and involved in multiple rebuilds for the last 45 years. He knows what he's talking about but we need your expertise...
                          We have been planning this rebuild for a year and a half, just didn't think it would come this soon.
                          No I don't think the shop is trying to lead us down the garden path...The engine is apart and headed to a machine shop...Want to put it back together as well as I can for the $ I have to spend.... Stock, Street, not Racing...
                          We have very specific desires for the rebuild, Lunatti cams, Speed Pro Pistons (yes we will replace), Scat Crank & Rods...
                          Unless someone tells us that what we want won't work...we trust your opinions.
                          My reply is not as technical as some but I think you get the idea.

                          Hope this helps...

                          Comment

                          • Patrick H.
                            Beyond Control Poster
                            • December 1, 1989
                            • 11643

                            #14
                            Re: Cam Specs for 69 & 70

                            Originally posted by Pamela H Haus (55255)
                            No I don't think the shop is trying to lead us down the garden path...The engine is apart and headed to a machine shop...Want to put it back together as well as I can for the $ I have to spend.... Stock, Street, not Racing...
                            We have very specific desires for the rebuild, Lunati cams, Speed Pro Pistons (yes we will replace), Scat Crank & Rods...
                            Unless someone tells us that what we want won't work...we trust your opinions.
                            My reply is not as technical as some but I think you get the idea.

                            Hope this helps...
                            "We have very specific desires for the rebuild"

                            And what are those desires? Other than posting some brand names you haven't really advanced our knowledge too far. Based on names alone it sounds like you're attempting to hotrod it, not go with a stock rebuild.
                            What Lunati cam? Which pistons? Why replace the crank and rods if they're not broken?

                            Honestly, for a stock rebuild you can reuse your stock crank, rods and other parts. You replace the wear items and refurbish the rest.
                            See Duke's post above if you want to improve the engine and get a lot more bang for your buck:
                            https://www.forums.ncrs.org/showthre...163#post630163

                            Patrick
                            Vice-Chairman (West), Michigan Chapter NCRS
                            71 "deer modified" coupe
                            72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
                            2008 coupe
                            Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.

                            Comment

                            • Duke W.
                              Beyond Control Poster
                              • January 1, 1993
                              • 15662

                              #15
                              Re: Cam Specs for 69 & 70

                              All OE replacement parts from Federal Mogul and/or Dana Corp. will work just fine for the 427/390, which is an excellent road engine. One of the only sure-fire ways to get more top end power without affecting low end torque or idle behavior is to massage the heads.

                              If you want to buy different spec parts from various vendors, then you are doing "engine system engineering", so you have to hope the "system engineer" knows your objective and what it takes to achieve it.

                              With the little I know about your car and this engine project one piece of advice I can give you is to not remove any metal from the block or heads unless absolutely necessary, but few "engine builders" take the time to make the necessary measurements to determine what really needs to be machined to correct real problems. They just start cutting metal.

                              This advice applies particulary to the block deck. If the block is original "matching numbers", machining the deck will be wipe out this data, and you have destroyed a good part of the provenence and value of your car.

                              Though your brother has decades of experience working on Corvettes, does he understand "restoration"? This assumes you have a relatively unmolested car and are not interested in turning it into a hot rod. I don't know. You've haven't given us enough details about your car or this project.

                              That doesn't mean that some of us don't want to improve engine performance. There are many tricks such as head massaging, stroking, and camshafts designed by NCRS members that can dramatically improve across the range engine performance without affecting idle behavior, normal day to day driving quality, or visual appearance, and at least one such "cheater motor" has achieved the coveted Duntov Award.

                              My sense is that you are moving too fast with too little knowledge, and you may ultimately regret the outcome.

                              Duke

                              Comment

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