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Flow numbers 492 heads

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  • Jerry G.
    Extremely Frequent Poster
    • April 1, 1985
    • 1022

    Flow numbers 492 heads

    Duke, I just got the flow numbers back on a set of stock 492 cast iron heads that i ported and relieved. it was interesting to try and figure out how to do this given that these heads areover 40 years old and the technical data about how to port these heads is mostly from the 60s and 70s. the data is;

    Intake Ehaust

    LIFT FLOW LIFT FLOW

    .100 127cfm .100 49cfm
    .200 172cfm .200 95cfm
    .300 208cfm .300 126cfm
    .400 230cfm .400 153cfm
    .500 239cfm .500 167cfm
    .600 239cfm .600 163cfm

    The flow were taken with 25 inch depressioin

    Inyeresting that flow comes on early and is maxed at .500 lift. The relieving process made a significant difference here. Jerry
    Last edited by Jerry G.; January 18, 2011, 02:48 PM.
  • Duke W.
    Beyond Control Poster
    • January 1, 1993
    • 15667

    #2
    Re: Flow numbers 492 heads

    Very good, especially on the inlet side. I assume the valves sizes are 2.02/1.6".

    The equivalent flow at 28" depression, 0.5" lift is 253/187 CFM (multiply by SQRT(28/25)) and the E/I ratio is 0.74, so a cam of equal duration on both sides or a few degrees more on the exhaust side is a good match, and for a vintage race engine the header primary tube ID should be in the range of 1 3/4 - 1 7/8".

    I assume these are fully ported - all the way from the valve seats to the head boundaries?

    By "relieving" do you mean grinding the sides of the chamber back to the cylinder bores to eliminate the head chamber overhang? That's important, especially on the exhaust side.

    Once the valve opens one-quarter of the valve diameter, the curtain area is the same as the valve head area,

    Pi*D*L = (Pi*D**2)/4 or L = 0.25D

    so the valve is no longer the limiting factor, and flow is limited by port geometry. That's about 0.5" on the inlet side and 0.4" on the exhaust side. If you removed the valves completely, you'd get about the same numbers.

    The slight reduction on the exhaust side at 0.6" lift is probably due to shrouding. I've see the same thing on the inlet side at less than 0.5".

    Duke
    Last edited by Duke W.; January 18, 2011, 06:47 PM.

    Comment

    • Jerry G.
      Extremely Frequent Poster
      • April 1, 1985
      • 1022

      #3
      Re: Flow numbers 492 heads

      They are 2.02 and 1.6. They are fully ported and relieved. To relieve them I ran a cutter down using the valve guide that had a shape designed to reduce the shrouding affect from the combustion chamber wall. In an earlier post you were the one that put me on to the importance of relieving, thank you.
      Now I need to get the flow numbers on my redesigned air meter for the fuel injection. This is exciting. Jerry

      Comment

      • Duke W.
        Beyond Control Poster
        • January 1, 1993
        • 15667

        #4
        Re: Flow numbers 492 heads

        I'd really love to see you run a 30-30 cam retarded four degrees, or a LT-1 cam retarded six degrees - a REAL vintage racing engine using genuine vintage parts.

        The LT-1 cam will yield better torque at 3000 with a little loss of power above 7000. With the 3927142 valve springs (designed for the 140 cam, 110 lbs. at the seat, 358 lbs/in rate) the valve train is good to at least 8000 and the valvetrain should be reliable. Or, if you can find an aftermarket beehive with the same characteristics, that would be fine.

        EA 3.5 Pro with the 30-30 cam shows about 480 gross HP at 6500 using 1 7/8" ID headers with very mild rolloff to 7500, and the best average power range is 6000-7500, which is were your transmission will keep the revs shifting at 7500. Peak torque is 430 at 5500 with 80 percent at 3000, and I used lower head flow numbers on the inlet side - about the same on the exhaust side.

        I had to reboot my office computer, so I lost my demo copy of EA 3.5 Pro, but if you still have yours give me a call and lets work out the configuration.

        I can probably also get another demo copy and load it on to my laptop. In the meantime, I can update my EA 3.0 model with your head flow data, but it will show higher numbers than EA 3.5 Pro.

        BTW, to simulate the FI system, I use "single plenum EFI" The program doesn't care if the fuel is added by continuous flow mechanical or pulsed electronic injectors. Both are pretty close in terms of power.

        I think the default flow efficiency of the runners in the single plenun EFI model is about 90 percent. If you flow test a manifold runner, we can compute the actual flow efficiency.

        The throttle body flow is what you measure for the air meter at 1.5" Hg. depression.

        I think using one of the OE cams and the 142 or equivalent spring will allow trouble-free operation with nothing more than a few lash checks between teardown/inspections every 25 hours.

        Duke
        Last edited by Duke W.; January 19, 2011, 10:20 AM.

        Comment

        • Joe C.
          Expired
          • August 31, 1999
          • 4598

          #5
          Re: Flow numbers 492 heads

          Jerry,

          Very nice numbers! Of particular interest are the inlet flow rates at 0.100" and 0.200" lift, which are 90% and 35% higher than ported LS6 heads using 2.02 and 1.60 valves! The flow numbers at 0.300" are remarkable also, as they show flows of about 10% more than those same LS6 heads. Compared to most race ported 461's with 2.02/1.60 valves, yours incredibly flow 50%, 20%, and 22% more at 0.100", 0.200" and 0.300", respectively, on the inlet side!

          Do you know what bore size was used for the test? 4.000? 4.030? 4.060? Was a short pipe used on the exhaust port? Was a clay form radius used on the inlet side?
          Last edited by Joe C.; January 19, 2011, 12:53 PM.

          Comment

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

            #6
            Re: Flow numbers 492 heads

            here are some numbers i got from GM years ago about vortech head unported. the newer ones are better if you are allowed to run them
            Attached Files
            Last edited by Clem Z.; January 19, 2011, 12:15 PM.

            Comment

            • Jerry G.
              Extremely Frequent Poster
              • April 1, 1985
              • 1022

              #7
              Re: Flow numbers 492 heads

              Originally posted by Clem Zahrobsky (45134)
              here are some numbers i got from GM years ago about vortech head unported. the newer ones are better if you are allowed to run them
              Hi Clem....I'm required by my santioning body to run original design "double hump" 461 0r 492 heads. I am getting more flow now out of these 492, that i've worked on, than the 461s that Byzinski did for me.

              Comment

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

                #8
                Re: Flow numbers 492 heads

                Originally posted by Jerry Gollnick (8575)
                Hi Clem....I'm required by my santioning body to run original design "double hump" 461 0r 492 heads. I am getting more flow now out of these 492, that i've worked on, than the 461s that Byzinski did for me.
                with a little work and some expoxy the "double humps" could be fabricated on and any head.

                Comment

                • Jerry G.
                  Extremely Frequent Poster
                  • April 1, 1985
                  • 1022

                  #9
                  Re: Flow numbers 492 heads

                  Originally posted by Joe Ciaravino (32899)
                  Jerry,

                  Very nice numbers!
                  Do you know what bore size was used for the test? 4.000? 4.030? 4.060?
                  Was a short pipe used on the exhaust port?
                  Was a clay form radius used on the inlet side?
                  4.030 , a short pipe was not used and the inlet was mated to the flow bench with their fixture. good questions, you've done this before.

                  Comment

                  • Jerry G.
                    Extremely Frequent Poster
                    • April 1, 1985
                    • 1022

                    #10
                    Re: Flow numbers 492 heads

                    Originally posted by Duke Williams (22045)
                    I'd really love to see you run a 30-30 cam retarded four degrees, or a LT-1 cam retarded six degrees - a REAL vintage racing engine using genuine vintage parts.

                    The LT-1 cam will yield better torque at 3000 with a little loss of power above 7000. With the 3927142 valve springs (designed for the 140 cam, 110 lbs. at the seat, 358 lbs/in rate) the valve train is good to at least 8000 and the valvetrain should be reliable. Or, if you can find an aftermarket beehive with the same characteristics, that would be fine.

                    EA 3.5 Pro with the 30-30 cam shows about 480 gross HP at 6500 using 1 7/8" ID headers with very mild rolloff to 7500, and the best average power range is 6000-7500, which is were your transmission will keep the revs shifting at 7500. Peak torque is 430 at 5500 with 80 percent at 3000, and I used lower head flow numbers on the inlet side - about the same on the exhaust side.

                    I had to reboot my office computer, so I lost my demo copy of EA 3.5 Pro, but if you still have yours give me a call and lets work out the configuration.

                    I can probably also get another demo copy and load it on to my laptop. In the meantime, I can update my EA 3.0 model with your head flow data, but it will show higher numbers than EA 3.5 Pro.

                    BTW, to simulate the FI system, I use "single plenum EFI" The program doesn't care if the fuel is added by continuous flow mechanical or pulsed electronic injectors. Both are pretty close in terms of power.

                    I think the default flow efficiency of the runners in the single plenun EFI model is about 90 percent. If you flow test a manifold runner, we can compute the actual flow efficiency.

                    The throttle body flow is what you measure for the air meter at 1.5" Hg. depression.

                    I think using one of the OE cams and the 142 or equivalent spring will allow trouble-free operation with nothing more than a few lash checks between teardown/inspections every 25 hours.

                    Duke
                    Duke My demosration copy timed out also. Before it timed out I went through the effort you suggested to fine tune the simulation to match my engine dyno data. I'd be very curious how the 30-30 would compare to the cam I'm currently using on this configuration. I came to the same conclusion you did on the use of the throttle body for inlet simulation. If you have a fax I can sent you the full printout from my last run on the system. I think you have my currewnt cam data. I have behive springs installed that are 180 closed and 310 full open. I plan to run a rev kit. Probably the 1:5 stamped rockers.

                    Comment

                    • Jerry G.
                      Extremely Frequent Poster
                      • April 1, 1985
                      • 1022

                      #11
                      Re: Flow numbers 492 heads

                      Originally posted by Clem Zahrobsky (45134)
                      with a little work and some expoxy the "double humps" could be fabricated on and any head.
                      say it isn't so! a racer masaging parts to be more competitive?? You sly old fox you sound like a real racer. This could be next years upgrade.

                      Comment

                      • Joe C.
                        Expired
                        • August 31, 1999
                        • 4598

                        #12
                        Re: Flow numbers 492 heads

                        Originally posted by Jerry Gollnick (8575)
                        4.030 , a short pipe was not used and the inlet was mated to the flow bench with their fixture. good questions, you've done this before.
                        The inlet discharges into a fixed bore, but the upstream end of the port is generally radiused with a molded clay "nacelle" or a nozzle to emulate the upstream conditions in the inlet manifold. Pressure or vacuum is applied to the fixed bore.




                        Your exhaust flow rates are lower than they should be, considering your very admirable 253 inlet cfm @ 0.500". I suspect that if a 6" tube was used on the exhaust port, that your exhaust flow would, in reality, be closer to 175 cfm.
                        Attached Files
                        Last edited by Joe C.; January 19, 2011, 01:29 PM.

                        Comment

                        • Duke W.
                          Beyond Control Poster
                          • January 1, 1993
                          • 15667

                          #13
                          Re: Flow numbers 492 heads

                          Originally posted by Jerry Gollnick (8575)
                          Duke My demosration copy timed out also. Before it timed out I went through the effort you suggested to fine tune the simulation to match my engine dyno data. I'd be very curious how the 30-30 would compare to the cam I'm currently using on this configuration. I came to the same conclusion you did on the use of the throttle body for inlet simulation. If you have a fax I can sent you the full printout from my last run on the system. I think you have my currewnt cam data. I have behive springs installed that are 180 closed and 310 full open. I plan to run a rev kit. Probably the 1:5 stamped rockers.
                          I lost the cam data along with the program, but I'm sure I have it in an e-mail. IIRC the cam was basically okay. In fact, most similar cams won't be much different. It's head flow, not the cam (within the range of typical racing cams of a given type) that make power.

                          So, assuming you dyno the engine, how about installing both a 30-30 retarded four degrees, and your existing cam. The 30-30 can use less valve spring than an aggressive solid roller. Then you can make the call as to whether the modest loss in performance with the 30-30 offsets all the valvetrain problems.

                          The 142 springs at 110 pounds on the seat would only be at about 270 pounds at .450" lift, which is what you get assuming a max rocker ratio of 1.44:1. That will sure reduce valvetrain loading.

                          To win, you have to finish!!!

                          I don't have a fax... can you scan and attach it to an email?

                          Duke

                          Comment

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

                            #14
                            Re: Flow numbers 492 heads

                            I plan to run a rev kit. Probably the 1:5 stamped rockers.[/quote]
                            the rev kits for flat tappet cams are very complicated because the lifers must be able to spin. NASCAR engine builders used them till NASCAR outlawed them. i built a rev kit for my 365 HP 64 corvette and i used very little spring pressure on the lifter when the lifter was on the heel of the lobe so the lifter would still rotate. i grooved the push rods so i could use valve keys to hold the spring retainer in place. i used the standard rev kit plate against the head. the one NASCAR used the springs pushed against the lifters BUT the spring was used with a ball bearing so the lifter and spring could rotate. i will check and see if i have a picture of the NASCAR one

                            Comment

                            • Duke W.
                              Beyond Control Poster
                              • January 1, 1993
                              • 15667

                              #15
                              Re: Flow numbers 492 heads

                              Your ingenuity is always impressive!

                              Duke

                              Comment

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