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  • Some project photos

    I know how much people here like looking at photos so having just got around to setting up a photobucket account I thought I'd share a few. More fabrication than machining strictly they show a sequence in the manufacturing of an inlet manifold to allow the mounting of motorcycle flat slide carbs on my sports car.



    This is the back plate cut out of 0.250" tooling plate.



    This is the mandrel, carved out of a lump of ally. I turned down some ally tube to appropriate i/d and o/d, annealed it, greased up the mandrel and pressed it into the tube. A gentle dressing over with appropriate hammers and the tube took on the shape of the mandrel.



    This was a trial weld onto an offcut of tooling plate.



    Bringing the shaped inlet runners/spigots together with the back plate on a steel jig ready for welding.

    More photos to follow.
    Last edited by Alan Smith; 10-23-2007, 11:15 AM.
    West Sussex UK

  • #2


    The carbs mounted.




    And the vehicle in question, although in fact this photo was taken before the M/C carbs were put on.
    Last edited by Alan Smith; 10-23-2007, 11:13 AM.
    West Sussex UK

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    • #3
      Originally posted by Alan Smith


      The carbs mounted.




      And the vehicle in question, although in fact this photo was taken before the M/C carbs were put on.
      Is that an original or a copy of the Lotus 7. Caterham perhaps?

      http://en.wikipedia.org/wiki/Lotus_Seven#Replicas

      A Super 7 for the 21st Century

      http://www.arielatom.com/?gclid=CKTu...FRa_WAodpim6Sw
      Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

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      • #4
        I hope you will also tell us all about getting the carbs jetted correctly.
        "four to tow, two to go"

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        • #5
          Nice work Allen, class act fabrication, good looking welds.

          Are those vacuum operated slides? if so thats good stuff, they cover the range very well, its carburation in about its most efficient form... Im guessing they are because I see where a shaft leads ahead of the slide, so it most prob. has a typical butterfly plate for controll and then the slides take over by sensing engine load and RPM and butterfly pos. ?
          Last edited by A.K. Boomer; 10-23-2007, 12:04 PM.

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          • #6
            Yeah what year is that? Wasn't caterham bought out by lotus in the early 90's? I dunno i could be way off ...

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            • #7
              Yes it's a Caterham. An HPC (High Performance Car) with a Swindon(Racing Engines) 218 Vauxhall 2.0XE engine. Caterham Cars bought the manufacturing rights from Lotus in the early '70s. We just (September 6th) celebrated the 50th anniversary of the marque, not bad for a car that can still out accelarate Porches and Ferraris!!

              I have to confess that the welding is not mine. I'd dearly love to have tig but it's way out of my budget with a queue of other desired toys taking presidence. I'm fortunate to have a specialist welding shop fairly close at hand and the guys that run it are keen bikers and sympathetic to my nutty ideas.

              The slides are cable operated, not the CD (constant depression) vacuum type. Very simple, but beautifully made and can give precise metering. Setting them up was a bit of fun. The guys at the rolling road I use were not really familiar with this type of carburator so we had to hunt around to find a motorcycle tuner to come and give a hand. Once we all got together we got it set up in a couple of hours. RR printout is below.



              Bear in mind this car weighs about 600Kgs, 201 BHP really shifts it!
              West Sussex UK

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              • #8
                Those carbs work better with an airbox in front of them. The distance from the air horns to the slide is very short so something to quiet the air in front of them is a power maker. Or longer horns at least. Those little short ones are made to be inside the air cleaner box.

                Nice job.
                Gene

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                • #9
                  Those look similar to some Keihn FCR (39mm) carbs I had on my Ducati 900SP back in the day. Some days I sure miss that bike...

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                  • #10
                    Those air trumpets are what came with the carbs for M/cycle applications. I made up some much longer aluminium air trumpets and had some spacers waterjet cut out of 1" ally plate. I think that gives an inlet tract length of 14.5" to the back of the inlet valve, great for a good torque curve.

                    The carbs are Keihin FCR 41s, as I said above , beautifully made.

                    One other job that had to be done was getting a new throttle spindle made up. This had to be farmed out as I don't have a mill or anything capable of precise drilling/allignment.

                    Talking of airboxes, this winters project will be an airbox. As run at the moment there is a foam Pipercross sausage filter which is outside of the bonnet (hood). The induction roar is horrendous when giving it beans and I'm sure contributing to my increasing deafness, so this box will hopefully attenuate the noise and will take air from a remote air filter from within the engine bay. Hopefully I can direct a stream of cool air in the filters direction.
                    West Sussex UK

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                    • #11
                      I'm sure that you know that airbox design is not for somebody new to induction science, lots of power in the right airbox.
                      "four to tow, two to go"

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                      • #12
                        Nice job - any picture of the Mandrel on it's own? I'm wondering how the mandrel comes back out of the tube after shaping it?
                        I did something similar with GSXR throttle bodies but I was in a rush so didn't make a mandrel - just shaped them with a vice & hammer. But it was a suzuki engine so had oval ports rather than cutouts for injectors.

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                        • #13
                          I just noticed the layout of that car, that has got to be one weird feeling bird to push in the turns, your ass is right above the rear wheels, it would be very strange to lose in a turn also, some abrupt g-forces I imagine...

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                          • #14
                            GN3dr, I'll post you up a piccy of the mandrel when I get home, just finishing off another sh*tty night duty.

                            A.K. interesting that you picked up on that. Having your bum almost over the rear axle means you pick up on what the car is doing very very early so in theory its easy to catch if you start to lose it in a corner. Going quickly round corners is what these machines are all about.
                            West Sussex UK

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                            • #15
                              I can see that good and I can see that bad, I could see it being Chaos in a recovery effort because its happening too fast, also its nice to keep tune with another aspect of the car -- The front end ,,, I always hated the datsun Z cars and many of the Jags just for that reason, To each thier own but when the speeds really get going its actually nice to be midship or even up a little further --- believe me, those indy or formula 1 catz know where thier tail is at all times just by the feel of what thier car is doing ------- They have too, and I might add extra extra critical in those rides for two reasons, One; the speeds that are achieved and Two; if thier ass end gets too loose thier goes thier ground effects because it abruptly upsets the flow dynamics and then it actually becomes an imposibility to regain control after losing it in a high speed turn...

                              Please dont take this the wrong way, Im just waking up with my morning coffee, I think your cars a trip and would be quite an experience to drive...

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