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Weber carb problem

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  • #46
    Re: Weber carb problem

    Donnie, bit disappointed that the supplier has not got back to me yet. I might chase him up this week, if only to quiz him on why the mixture screw has to be turned clockwise beyond the 'one turn from home' position - probably at the half-turn position, with the spring under the screw-head nearly locked up. This usually means the pilot jet is the wrong size I think. When I spoke to him on this issue originally, he said that it could also be a sympton of air-leaks via manifold etc or zero cam clearances as OHC engines tend to do after big mileages. I am sure I checked this out about a year ago, and all was well in this area.

    That stud you referred to is non-adjustable, and is part of the mechanism for increasing/decreasing the revs on the little cam. Very strange design! The one on the Grannie carb did provide some adjustment.

    The 2-chokeknob installation is working well, and gives me precise control on the engine. With the manual-choke conversion I fitted to the Grannie carb, I remember that it was always a nuisance gettting the revs to die down a few minutes after starting. Had to keep jabbing the acceleratot pedal to get the ratchet cam of the carb to release the screw. Not good early morning living in a quiet cul-de-sac!

    One problem that has come back is the running-on when the engine is turned off. Drat it! As a double check, I'll remove the plumbing and the expensive anti-run valve, and make sure there is no c**p partly blocking this area.

    Cheers
    Mike

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    • #47
      Re: Weber carb problem

      I was a bit premature in saying that the new carb is running well. I got it tickover reasonably well, but when I took it for a modest run to work today (the first journey since finishing the installation, I was less than happy with the way the engine 'picked up' from tickover revs. There was a distinct flat-spot at around 1000-1200rpm, even tending to stall as I let out the clutch. Pressing the accelerator hard down overcame this, but the engine had to rev to at least 1500rpm and preferably 2000rpm to guarantee that it would pull away from standstill reliably. Not good at traffic lights and roundabouts to have this doubt!

      I rang Fast Road Cars who supplied the 32/36 carb, highlighting this problem. I also told him of the need to screw the mixture screw clockwise until it was about a half-turn from fully 'in', to obtain a half decent tickover. He was puzzled with the mixture screw setting, being in conflict with the engine's need for an extra squirt of petrol to make it take off from standstill.

      The guy suggested that the camshaft may be a quirky one, and not the original standard Ford version, and that it might not run cleanly at low revs. The big Grannie carb would have compensated for this 'flat-spot', by pumping in loads of fuel, and I would not have noticed this before now quite so much. Whereas the 32/36, being a bit leaner with petrol, would not work so well in this instance. He was happy to supply another pilot jet, but wanted me to check out the camshaft first.

      He also suggested that my valve clearances were possibly inadequate, and were worth checking. I would admit that when I just did this, some of them were less than the Haynes figures = 10 thou exhaust and 8 thou inlet.

      This begs the question: does one measure the gaps when the tip of each valve is at the top, or when the adjacent exhaust & inlet valves form a V as recommended by Haynes? Also, is this done with a hot or cold engine? Haynes doesn't say.

      Anyway, to satisfy the camshaft query, I'll start a new message specifically asking for help in identifying my existing camshaft.

      What started off as a straightforward swap-over of carbs is now excalating into something more complicated. Oh the joy of running a kit!

      Cheers
      Mike

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      • #48
        Re: Weber carb problem

        Doug had a play with Berlinetta on Sunday. He cleaned the points and re-set them. Fitted a set of new plugs. No 4 plug seemed a bit loose! While fiddling about he opened the throttle really wide suddenly while the air filter was off and there was a large backfire with flame while he had his head over the carb! Flames missed but he jumped! Car seems to be running better now! Test drive followed and its running quite well inspite of a worn carb. It also seems to have more power than for a while.

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        • #49
          Re: Weber carb problem

          Liz, just a quick thank-you for the calendar received today. All looks very good!
          Cheers
          Mike

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