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Failed design

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  • Michael C.
    Frequent User
    • September 25, 2012
    • 63

    Failed design

    Why don't you think this hood treatment for 67 tri-powers never made it to production? Anyone tried to fabricate this?
    Attached Files
    1967 Corvette L71 Coupe
  • Michael W.
    Expired
    • April 1, 1997
    • 4290

    #2
    Re: Failed design

    They needed all the BB hoods they could get for SB cars.

    Comment

    • Michael G.
      Extremely Frequent Poster
      • November 12, 2008
      • 2155

      #3
      Re: Failed design

      My guess, since it was drawn on April 14, is that the design was initially proposed on April 1 to fix the tri-power's kneuten valve N87 nitrogen leakage problem....

      Comment

      • Duke W.
        Beyond Control Poster
        • January 1, 1993
        • 15610

        #4
        Re: Failed design

        Originally posted by Michael Garver (49693)
        My guess, since it was drawn on April 14, is that the design was initially proposed on April 1 to fix the tri-power's kneuten valve N87 nitrogen leakage problem....
        I think this was discussed a few years ago and the reason may have been that it failed GM's severe water intrusion test.

        I had a friend years ago whose Scirocco experienced hydraulic lockup after a truck next to him doused the car with water going through a big puddle. I guess VW's test wasn't as severe as GM's.

        Duke

        Comment

        • John H.
          Beyond Control Poster
          • December 1, 1997
          • 16513

          #5
          Re: Failed design

          Originally posted by Duke Williams (22045)
          I think this was discussed a few years ago and the reason may have been that it failed GM's severe water intrusion test.
          That's correct - I was in the Corvette Group at the time, and I remember when the prototype hood failed the Proving Grounds Water Ingestion Test; it was a foregone conclusion (just from examining the design) that it would fail, and the test confirmed it. Sales loved it, Engineering didn't (just like sidepipes).

          Comment

          • Michael C.
            Frequent User
            • September 25, 2012
            • 63

            #6
            Re: Failed design

            Was it similar to the L88 in design theory? Just triangular instead of round? I find this stuff fascinating. Thanks for share the history.

            Mike C.
            1967 Corvette L71 Coupe

            Comment

            • Richard M.
              Super Moderator
              • August 31, 1988
              • 11302

              #7
              Re: Failed design

              Originally posted by John Hinckley (29964)
              That's correct - I was in the Corvette Group at the time, and I remember when the prototype hood failed the Proving Grounds Water Ingestion Test; it was a foregone conclusion (just from examining the design) that it would fail, and the test confirmed it. Sales loved it, Engineering didn't (just like sidepipes).
              If they setup a trap door with a water exit could it have worked? Cost prohibitive probably, but it's a cool design and too bad it didn't get used. A true uniqueness and we'd have another thing to pay big bucks for when restoring the 400's or the 435's.

              What about the Chevelle Cowl Induction? How did that work against water? I'm unfamiliar with it's design.

              Why didn't engineering like the sidepipes? Was it performance loss issues?

              Comment

              • John H.
                Beyond Control Poster
                • December 1, 1997
                • 16513

                #8
                Re: Failed design

                Originally posted by Michael Cipolla (55475)
                Was it similar to the L88 in design theory? Just triangular instead of round? I find this stuff fascinating. Thanks for share the history.

                Mike C.
                Mike -

                Nope - the L-88 drew air from the rear of the hood - the cancelled design drew it through the opening at the front of the stinger.

                Comment

                • John H.
                  Beyond Control Poster
                  • December 1, 1997
                  • 16513

                  #9
                  Re: Failed design

                  Originally posted by Richard Mozzetta (13499)

                  What about the Chevelle Cowl Induction? How did that work against water? I'm unfamiliar with it's design.

                  Why didn't engineering like the sidepipes? Was it performance loss issues?
                  Rich -

                  The Chevelle cowl induction hood drew air from the rear, like the '69 ducted hood option on the Camaro. Engineering didn't like the sidepipes due to the restriction caused by the 1-7/8" core pipes, which were actually 1-5/8" across the peaks of the perforations; the stock under-car exhaust was much less restrictive.

                  Opening the front of the stinger was useless anyway from a performance perspective - there was no "ram-air" effect until well over 100mph, as the opening was in the boundary layer of essentially static airflow (which is why Pro Stock cars have their scoop intakes 18" above the hood surface). The only benefit of a functional surface-level hood scoop is from ambient instead of underhood air; colder air in the intake charge is generally worth about a 1% power increase for each 10*F reduction in air charge temperature.

                  Comment

                  • Duke W.
                    Beyond Control Poster
                    • January 1, 1993
                    • 15610

                    #10
                    Re: Failed design

                    I'll add that the actual static pressure on the hood is negative, but postive at the base of the windshield, and this was known at the time though at legal road speeds it's only a few inches of water. Given the front opening and water ingestion issue, it was just a bad design, period.

                    The Chevelle cold air induction on the hood just forward of the windshield has a vacuum valve that I believe only opens it up at WOT.

                    Duke

                    Comment

                    • Michael C.
                      Frequent User
                      • September 25, 2012
                      • 63

                      #11
                      Re: Failed design

                      John, I see. Seems like the design should have been the same as the L88 with the only difference being a triangular air filter. Still pull air from base of windshield. Too bad they cancelled it.
                      1967 Corvette L71 Coupe

                      Comment

                      • Robert R.
                        Very Frequent User
                        • May 31, 1975
                        • 358

                        #12
                        Re: Failed design

                        It would be similar to the 73-75 Corvette Cowl Induction system, correct?
                        Did that setup yield any extra hp?

                        Comment

                        • Michael J.
                          Extremely Frequent Poster
                          • January 27, 2009
                          • 7073

                          #13
                          Re: Failed design

                          This is very interesting, especially since numerous other manufacturers, like Mopar and Ford, had many "Ram Air" cars in the day. I have two of them, and they handled the water intrusion simply and effectively.
                          Big Tanks In the High Mountains of New Mexico

                          Comment

                          • Duke W.
                            Beyond Control Poster
                            • January 1, 1993
                            • 15610

                            #14
                            Re: Failed design

                            Originally posted by Robert Ricchio (599)
                            It would be similar to the 73-75 Corvette Cowl Induction system, correct?
                            Did that setup yield any extra hp?
                            SAE net rated output is the same with or without cold air induction because it's always corrected to specific atmospheric conditions.

                            Most of the time with under the hood induction, power will be less because the induction air is hotter than ambient,
                            and less dense than SAE standard air density.

                            Cold air induction means that actual output depends on actual ambient air density, so cold, dry air will definitely make more power than SAE standard air density.

                            Air density varies most with temperature over short time periods, and the rule of thumb is one percent more power for every 10F drop in inlet air tempeature.

                            Duke

                            Comment

                            • Jeff P.
                              Expired
                              • October 21, 2011
                              • 287

                              #15
                              Re: Failed design

                              John,

                              I'm looking at the Hooker Super Competition Sidepipes Design and can't see the Restriction problems if the GM Engineering Team would have used this Design. All the Header Pipes are the same length, meaning Tuned Exhaust dumping into a 4" muffler for anti reversion and noise reduction. Big increase in horsepower and Torque using individual pipes at the Heads instead of a Stock Restricted Exhaust Manifold, is the way they are designed today on the new vettes. Yes the small horsepowered cars like the stock manifolds. The Failed Design of the Air Induction could have been redesigned for street and Race Design.

                              Comment

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