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Thread: carb "dead spot"

  1. #106
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    Default Re: carb "dead spot"

    I have the same problem on mine, not quite as bad as Chris but noticeable enough. I won't use Powerspark as I bought a new electronic dizzy from them for my Pinto engined Capri and it was a bag of crap. The shaft was binding and could hardly be turned by hand. As for the arrogant individual who owns the company and who I had the misfortune to have to deal with, I'll leave my opinion of him to your imagination.

    I ended up fitting an Accuspark ignition module to the original Capri dizzy and it's worked a treat ever since. I also disconnected the vacuum from the carb and set the ignition to around 15 deg advance on the advice of an old school mechanic who races old Fords and has a rolling road here in North Wales.

    Anyway, back to Landrovers. I've also fitted the Accuspark module to the S3 dizzy, binned the points and condenser and replaced all the plugs, leads, cap and rotor arm along with a new set of NGKs. Coil is also new. Engine starts first time every time and ticks over like a Rolex but does have this annoying flat spot that goes away if you pull the choke out slightly. Carb has been overhauled as Chris did with his but not made a big difference. It's more noticeable on light throttle when driving such as in slow moving traffic and can be a right PITA as it kangaroos which along with the transmission backlash makes for an interesting ride .

    I do have a bit of blue smoke on startup and assume this is due to worn valve stem seals but when running this clears quickly and cylinder compressions are generally good. I've put the flat spot down to an old and worn engine which will be rebuilt with a skimmed head to increase the compression slightly, new cam etc when the car gets it's restoration.

  2. #107
    Consultant Richie_asg1's Avatar
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    Default Re: carb "dead spot"

    What carb are you running? And is it the same as Chris has?
    From my dealings with my weber, I know there is a transition between the idle circuit and when the throttle opens onto the primary jet. I suppose if the settings as to when this happens is wrong you will either get too much or not enough fuel at that point. The fuel pump is supposed to help with this by injecting a squirt of fuel when this happens, which on the weber is driven by a cam at the front. These cams are replaceable to match what you are aiming for in regards timing and quantity of the squirt. The jet is replaceable but is usually buried deep in the thing so seldom needs messing with.

  3. #108
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    Default Re: carb "dead spot"

    Quote Originally Posted by Richie_asg1 View Post
    What carb are you running? And is it the same as Chris has?
    From my dealings with my weber, I know there is a transition between the idle circuit and when the throttle opens onto the primary jet. I suppose if the settings as to when this happens is wrong you will either get too much or not enough fuel at that point. The fuel pump is supposed to help with this by injecting a squirt of fuel when this happens, which on the weber is driven by a cam at the front. These cams are replaceable to match what you are aiming for in regards timing and quantity of the squirt. The jet is replaceable but is usually buried deep in the thing so seldom needs messing with.
    Original Zenith on mine.

    Interesting information on the Glencoyne website.

    Easy to identify with its large sloping float chamber. The 36IV is a simple, almost primitive device, but well suited to the 2286cc petrol engine. It suffers from throttle spindle wear, which allows excess air to be drawn in at small throttle openings, giving hesitant performance at low speed. There is an 'O' ring between the upper and lower body which can perish or split leading to fuel flooding into the intake. Blocked jets are not unknown - the one that seems to suffer most is the accelerator pump jet, leading to hesitation and flat spots when the throttle is opened from idle. Replacement Zeniths are widely available - I believe the originals are no longer being made, but there are several reproductions also available. Beware as some of these are of very poor quality. You may be better to have yours rebuilt - there are several carb specialists who can do this. A new Zenith can be fitted as a direct replacement for a Weber 34ICH (see below). It can also replace a Solex 40PA, but for this application you will need an adaptor plate and throttle linkage from a Zenith or Weber-equipped vehicle.

  4. #109
    Moderator DarrenH's Avatar
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    Default Re: carb "dead spot"

    Quote Originally Posted by Bigj66 View Post
    I also disconnected the vacuum from the carb and set the ignition to around 15 deg advance on the advice of an old school mechanic who races old Fords and has a rolling road here in North Wales.
    that because race cars are only concerned with wide open throttle and max effort

    not disagreeing with you, mind you, because thats exactly the advice and setup i got from my local webcon dealer/rolling road. vac advance is for part throttle economy, and as above, making changes to low/mid throttle angle ignition based on engine load.
    Drives: 1982 series 3 88" station wagon

  5. #110
    Forum Approved Trader christofloffer's Avatar
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    Default Re: carb "dead spot"

    quick question, i have just dumped the old 25D distributor on. yet to start it as i cant figure the wiring. there is only one connector on the side, is that a positive or negative?
    i cant seem to find an answer and i dont want to fire it up with the wiring wrong. i thought it may be a negative back to the coil but i dont know.
    Chris
    1977 series 3 ex mod (FFR) 109 2.25p 12v HRTC hard top "phil"
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  6. #111
    Engineer solemnwarning's Avatar
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    Default Re: carb "dead spot"

    Assuming negative earth, its the negative terminal on the coil (i.e. opposite the wire to the ignition switch).
    1970 Series IIA 2.25 petrol - WIP

  7. #112
    Forum Approved Trader christofloffer's Avatar
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    Default Re: carb "dead spot"

    thanks for that, got it up and running, stopped once it started to get dark though. first impressions arent as good as it could be. it sounds a bit more lumpy on the points but i havent had a chance to get the timing strobe out. so perhaps that will get sorted. the dead spot is still there though, seems a bit more erratic than before. i will get the strobe on it tomorrow and see how it fares.
    Chris
    1977 series 3 ex mod (FFR) 109 2.25p 12v HRTC hard top "phil"
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  8. #113
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    Default Re: carb "dead spot"

    Quote Originally Posted by DarrenH View Post
    that because race cars are only concerned with wide open throttle and max effort

    not disagreeing with you, mind you, because thats exactly the advice and setup i got from my local webcon dealer/rolling road. vac advance is for part throttle economy, and as above, making changes to low/mid throttle angle ignition based on engine load.
    I was surprised at how good it is when set up like that. The car is a daily driver and not raced (as such��) so it needs a smooth and steady idle and decent pick up which it has.

  9. #114
    Forum Approved Trader christofloffer's Avatar
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    Default Re: carb "dead spot"

    right then, i have been out today with had a play with the timing. the strobe is definitely coming in handy still, glad i took the advice and bought one. i have got it spot on (that little adjuster on the 25d is great) and it does seem to have had an impact. the dead spot is still lurking there but its quicker and i can apply the throttle in a more gradual but still pretty fast way that avoids it. i think its about time for a test run and see how it fares under load. provided of course that its not snowy. yes i know the irony is daft, but as it is a little naughty to take it out the last thing i need is to have someone run into me and open a can of worms. doubly annoying as i love the snow.
    it definitely sounder smoother and perhaps a little more gutsy with the powerspark on it when the revs were up, but as long as it works i can come back to that later.
    Chris
    1977 series 3 ex mod (FFR) 109 2.25p 12v HRTC hard top "phil"
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    Default Re: carb "dead spot"

    Strobes are great on new engines, problem is timing chains like all chains get longer as they wear, this changes the ignition point in relation to piston movment, which for the sparky bit is the key point that matters. hence, it generally plays to set it statically, confirm its some were near with the strobe, then try a tweak one way or the other and simply go by feal on a drive, mines getting to the point that i really must check the timing chain, because the strobes showing that at point of best performance - economy the timing pulley marks miles off were it should be!

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    Default Re: carb "dead spot"

    well well well, took out for a test run and she drives nicely! no sign of the dead spot, certainly no lack of power, no kangaroo juice and no major catastrophes. didnt go far obviously but i had on the drive warming up for a bit first to make sure she was up to temp right from the start. she is a bit smokey on idle before i went out which concerns me as old vehicles have a visual check on exhaust rather than an emissions test dont they? but she might just need the run out there to give the engine a little work out.
    so i will be booking her in again on monday and we will see if i actually get to the test this time.
    Chris
    1977 series 3 ex mod (FFR) 109 2.25p 12v HRTC hard top "phil"
    My work: The emporium of the useful and curious http://emporiumoftheusefu.wixsite.co...umofthecurious
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  12. #117
    Engineer phoenixdave's Avatar
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    Default Re: carb "dead spot"

    That's good to hear at last Chris! Regards smoke and the MOT, as far as I remember up to about '73 it's visual test only, after that up to some time in early 80s it's a fairly generous CO reading, but after that the standard is quite a bit more stringent. The smoke at idle might go away when you start using the engine, just try not to let it idle for ages just before the test so you don't build up oil in the upper cylinders. David
    1982 ex-mil 109 2 1/4 petrol on lpg series III, 'Phoenix'

    1983 2 1/4 diesel 88" series III, 'Willy', currently in bits.

  13. #118
    Moderator DarrenH's Avatar
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    Default Re: carb "dead spot"

    visual test is Vehicles first used before 1 August 1975

    good result on the testing. so after 8 pages, it was just a warn or dodgy distributor ?
    Drives: 1982 series 3 88" station wagon

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    Default Re: carb "dead spot"

    i'm not sure to be honest. it wont be worn as it was brand new, but dodgy is an option. doesnt make much sense though as it sounded happier at idle and when holding the revs with the new dizzy. the dead spot is still present at idle too, its just quick and easy to drive around with the old dizzy on. obviously there is something not quite right in the set up of the electronic dizzy which makes a very small hesitation into a stall happy dead spot. i will have to get on to powerspark and see if they have any bright ideas. if i can get it through a test and be able to use it for the house move i will be happy. i can always come back to improvements later.

    the one thing the old dizzy has over the electronic one is that fine tuning for the timing. the new dizzy was backed right up on its rotation adjustment. so perhaps the root of it is the timing itself. who knows what has been messed with in the past.
    Chris
    1977 series 3 ex mod (FFR) 109 2.25p 12v HRTC hard top "phil"
    My work: The emporium of the useful and curious http://emporiumoftheusefu.wixsite.co...umofthecurious
    Proud member of the YCHJCYA2PDTHFH Club

  15. #120
    Moderator DarrenH's Avatar
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    Default Re: carb "dead spot"

    my dizzy has 2 adustments, the slotted hole between the base plate and engine block, but also you can slacken a clamp between the dizzy and its baseplate and effectively rotate it 360 deg
    Drives: 1982 series 3 88" station wagon

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