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A head design I was thinking of, and why it won't work

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    A head design I was thinking of, and why it won't work

    It's often brought up how 'twin-cam heads are very big, much bigger than a rocker head', and people are correct.
    But are they?
    I can a think about it and when you have a look at it, the cam-on-bucket system is a bit taller than a rocker-type but not a huge amount - the different is really not so much the valve actuation but the way the head itself flows air. Multi-valve heads are usually always a tumble & dump style and those have the inlet port coming down onto the valve at as very steep angle as possible and this is what makes the head 'tall'.
    If you have a look at a cross-section of a Toyota head you can see how steep that angle is ->



    Some of the older heads had more horizontal ports, like an earlier version of the same engine ->



    But with a tumble & dump type port, basically the steeper the port the better the airflow ..... so the good heads really are quite tall.

    The other type, the swirl port, are much more compact vertically as they don't come down onto the inlet valve at much of a vertical angle, but more sideways to get the airflow to swirl around the inlet valve, like this LS7 head ->



    By using a swirl port is allows the head to be quite a bit shorter, and you again pick up a little bit with the more compact valve gear.

    Anyway, I got to thinking and wondered if you could make a multi-valve head a full-on swirl type, to make it more compact. You'd get a lot of valve area for good breathing, a good-shaped chamber for good combustion, and the simplicity of cam-on-bucket all in a fairly compact head.
    To do this, instead of siamesing the bifurcated ports from each inlet valve you'd have to spread them apart and so the inlet ports between each cylinder would be paired. So far, pretty neat. But then the cylinders at the end would have a single port for the inlet valve at the end. So for a four-cylinder head (4-pot of half a V8) you'd effectively end up with three large ports in the middle and two smaller ones at the ends .... not so neat but certainly not impossible.
    I drew this rough diagram last night ->


    (just drew the inlet side)

    There'd be problems with interference from the inlet pulses in one cylinder affecting the neighbour one, but Chevys have lived with that for decades so that's liveable.

    The side vew is pretty rough 'cause I'm crap at drawing stuff on a graphics program but you should get the idea.



    (Again just drew the inlet side, and the port should be a bit shorter)

    So it's looking fairly compact now and can still breath pretty well.

    The problem is this though .... With the way the swirl works, it'd blow the mixture away from the spark plug and up against the cylinder wall. There'd be big problems with getting the thing to fire properly at increasing revs.
    Direct injection would probably help, but I don't know enough about it.
    Anyway, that's what I've been wasting a few brain CPU cycles on.

    #2
    cool story hansel.

    Comment


      #3
      Is this still for sale?
      Originally posted by Kiahatsiu
      Dear Fidel,
      Well, enough small talk, how is the corn chute?
      Regards
      Kia.
      Originally posted by rolin7
      the car is basically a drunk guy from Toowoomba with an empty VB case on his head.
      Originally posted by tomvale13
      maybe don a stackhat, a cardigan, wear a cheese cake as underpants and see how it goes

      Comment


        #4
        how do they go with something like the v8 IRL aurora heads?
        Originally posted by Buford T. Justice
        This happens every time one of these floozies starts poontangin' around with those show folk fags.

        Comment


          #5
          Looking at Nissan VG30DE/T/TT heads Bill the width has a lot to do with the twin cams and their drive arrangement. With the cams are sitting on top of buckets a lot of extra width is created, a single overhead cam and rocker arrangement is much more compact.
          Richard's DatsunZ lappin LakesidZ http://www.youtube.com/watch?v=47OSh...&feature=g-upl

          Comment


            #6
            Originally posted by 260DET View Post
            Looking at Nissan VG30DE/T/TT heads Bill the width has a lot to do with the twin cams and their drive arrangement. With the cams are sitting on top of buckets a lot of extra width is created, a single overhead cam and rocker arrangement is much more compact.
            True, but that's the 'old' way of doing it. Using scissor-drive gear inside the head cam-to-cam they're pretty compact and the valve are more vertical, which is what you want anyway.

            Comment


              #7
              Originally posted by Billzilla View Post
              True, but that's the 'old' way of doing it. Using scissor-drive gear inside the head cam-to-cam they're pretty compact and the valve are more vertical, which is what you want anyway.
              Example pics of these type heads?

              Comment


                #8
                these are the motors i was talking about.

                Originally posted by Buford T. Justice
                This happens every time one of these floozies starts poontangin' around with those show folk fags.

                Comment


                  #9
                  Originally posted by DaveBxGT View Post
                  Example pics of these type heads?
                  I don't have a good photograph of one, but here's a 7AFE head on a mate's off-roader.



                  The head is only a little bit wider than the block.

                  Comment


                    #10
                    Originally posted by rusty
                    fuckheads, that shit is past old. if i was a mod youd both be banned.
                    yet it seems your post is just as useful.

                    Thanks for your contribution.

                    So Bill, can we expect some more port design stories in up and coming Race magazines?

                    Comment


                      #11
                      Originally posted by carazy View Post
                      So Bill, can we expect some more port design stories in up and coming Race magazines?
                      Up to Nero.

                      Comment


                        #12
                        Originally posted by Billzilla View Post
                        I don't have a good photograph of one, but here's a 7AFE head on a mate's off-roader.



                        The head is only a little bit wider than the block.
                        That's a lot of bolt's on the airbox!

                        Comment


                          #13
                          Originally posted by Billzilla View Post
                          True, but that's the 'old' way of doing it. Using scissor-drive gear inside the head cam-to-cam they're pretty compact and the valve are more vertical, which is what you want anyway.
                          Yeh but the point is that with angled valves a twin cam and bucket arrangement takes up more width than other designs. So no matter how narrow you may design a head with that arrangement, without it the head could be narrower still.

                          On the swirl design taking the mixture away from the spark plug, are you absolutely sure about that? Because I can't see that it automatically follows in every instance.
                          Richard's DatsunZ lappin LakesidZ http://www.youtube.com/watch?v=47OSh...&feature=g-upl

                          Comment


                            #14
                            Originally posted by 260DET View Post
                            Yeh but the point is that with angled valves a twin cam and bucket arrangement takes up more width than other designs. So no matter how narrow you may design a head with that arrangement, without it the head could be narrower still.
                            How much narrower than the block do you want it to be?


                            Originally posted by 260DET View Post
                            On the swirl design taking the mixture away from the spark plug, are you absolutely sure about that? Because I can't see that it automatically follows in every instance.
                            Not entirely sure, it'd need for hefty CFD work to test all that stuff and I don't have access to that. Gotta do it in my head and I reckon the chamber mixtures wouldn't be homogenous enough - That's one reason the tumble & dump ports work so well, they give excellent mixing.

                            Comment


                              #15
                              Is that the ~280 HP 7AFE Bill?

                              Comment

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