Conference terri::cars_uk

    Do the carb needles match the cam profile? It sounds to me that the
    mixture is too rich on tick-over, and a different needle would fix
    that. Assuming it's a standard cam, you should have no problems
    finding a replacement. Bear in mind that the needles and guides do
    wear, and it sounds as if your carbs might need a rebuild kit. They're
    easily available from specialists by mail order, and are relatively
    inexpensive.
    
    Cheers, Laurie.

    The contact breaker points gap was not on your list (also known as
    dwell) setting these correclty cured the slight missfire on my spitfire
    (and increased power!).
    
    Paul

    Opps, another idea -
    
    What about the float levels in the carburrators - are they correct ?
    
    Paul
    

    thanks for the replies so far.
    
    re. 1 The carbs I have overhauled with new spindles and the usual
    jet-centering etc. The needles/jets I have not replaced but hope to shortly (H6 are
    recommended with K&N filters). However the carbs are on the weak side
    if anything on (hot) tickover. Exhaust tends to be black after a long
    fast run. but grey after the same run at 30-40 --- sounds like
    needle/jet trouble there...
    
    re .2 Point dwell is ok 
          However when setting the strobe timing the mark wont stay steady
          even though this is not evident in the engine sound.
    
    re .3 I bought new floats/needle valves for the carbs however they
          are completely plastic and non-adjustable for float level
    
    
    What about plug fouling, do you agree that that is happening?
    
    Keep 'em coming
    
    Brian.
    

    Here's another....
    
    What about your vacum advance / weights on the distributor - does it
    work properly. - springs might be sticking or of improper grade.
    
    ...I'm at a loss otherwise
    
    Paul

    If the timing fluctuates at idle the bushings in the distributor needs to
    be replaced.  To verify this simply remove the distributor and move the
    top of the distributor shaft back and forth.  there shound not be any
    movement and I suspect there will be.  This has happended to me with a
    bosch distrbutor on my 1600 Alfa Duetto.  I replaced the distributor
    and added an electronic pointless system.  The idle is smoother with
    better gas mileage.
    
    Al 

    Probably nothing to do with it as I havent a clue about engines and the
    like, however my jeep had the same sounding problem and all it was, was
    that the fuel filter was clogged. The engine seemed to have a mind of
    its own. Is the filter clean? 

    re -.1
    
    That's actually not as dumb as you think - a blocked fuel filter
    (partially blocked) could have that effect when the higher revs are
    requested from the engine and not enough fuel gets through.
    
    Had that one before on the spitfire....
    
    Paul

    RE: .7
    
    Not so daft actually, but in this case, the engine is fine at higher
    revs, which is what leads me to believe it's jetting. It's also
    possible, thinking about it, that the coil could be a bit iffy. If it's
    old, consider putting on a Lucas Sports coil; I forget the exact name,
    but they do sell them cheaply in Halfords. The Sprite one is the
    cheapest.
    
    Cheers, Laurie.

    RE:  New floats are plastic and not adjustable.
    
    The way to adjust the float in this case is to shim the jet with the
    proper washer.  If you bought new bowl jets they should have come with
    a couple different thicknesses of washers.  If they did not, your local
    auto parts store should stock them for a couple p each.
    
    This is worth checking.  If you are running with no washers, or too few
    washers, then the float will be too high and you'll run too rich.
    
    RE: .last
    
    I recently replaced the coil in my 1974 midget with a new one (of stock
    specs) it made a huge difference.  The tickover increased by about 100
    RPM and performance improved as well.
    
    Also, a new condensor isn't always a good condensor.  I've heard more
    than once about them being DOA.  You might install the old one, or
    another new one, and see if the problems persists.
    
    Best of Luck,
    -AL
    
    1974 midget
    1957 MGA Roadster (in small piles around the garage 8^)
    

    One again thanks for those replies,
    
    Unfortunately I have not been able to try out any of your suggestions
    since I first entered the note. But over the weekend I'll get a chance.
    
    Definately the coil could be dodgy (it's 1967 vintage) - Ill replace
    that in any case.
    
    Re the floats: I didnt check the clearance and I think you are possibly
    on the right track here I just put them in not thinking what those
    little washers with the needle seats were for !!!!
    
    In a previous note I mentioned having a problem with flooding float
    bowls. This I fixed by installing a filter king c/w petrol filter
    I didnt adjust the pressure setting on this at all but I am not
    experiencing fuel starvation.
    
    Re the distributor: I had to replace the Vacuum Advance mechanism
    (Lucas 25D dist.) but the bearings seemed ok No-play, 
    (I'll check this again)  the dwell
    stays steady so the lobes on the dist. cam must be ok but still
    theres the timing not staying steady.
    
    Ill post the outcome of my mechanical endeavours on Monday
    In the meantime if anyone has any more suggestions ......
    
    
    Cheers,
    
      Brian.
    
      

    If you're replacing the coil anyway, make sure it's a Lucas Sport. I
    think the Bosch equivalent is a Bosch Blue, but my memory is hazy.
    
    Laurie.

    Aldon Automotive in the west midlands do an excellent electronic
    ignition package from the state called "Ignitor", it's incredibly
    compact, maintenance free and will fit an A-series dizzy no worries. I
    can't remember the exact price, but it was around the �50 mark. Well
    worth it, I can say.

    Me again.....
    
    UNfortunately Over the weekend I did'nt get a chance to get working on
    the Sprite, Im going on holidays tomorrow and will report on my
    progress with the car when I come back.
    
    CHeers,
    
      Brian.

    I've just re-read the base note and realised that I've had more or less
    the same problem. It started when I removed an air scoop from under my
    car that was keeping air circulating around the engine bay (well, a
    rock removed it...).
    
    Could your air filters be sucking in hot air? Is there a heat shield in
    place over the exhaust manifold? A-series are quite bad in this respect
    (having inlet and exhaust all on one side of the head).
    
    Dan$not sure if this cured the problem since I had the car tuned
    afterwards, but y'never know..... Good luck!

    I though hot air in carbs was normal - hot fuel though can cause
    problems - something to do with density and ignition temperature.
    
    Paul

    The hotter the air, the less dense, and this alter the mixture.
    Hot fuel is also a problem, but for entirely the different reasons - it
    can get vapour lock and fuel starvation problems (I had this problem
    before until I lagged the fuel pipes!).
    
    My engine bay does get rather hot compared to a front-engined mini!
    
    Cold air = POWER! (haaar haar haaar evil cackle!)

    
>>>    Cold air = POWER! (haaar haar haaar evil cackle!)


	That is why real Turbo charged cars have intercoolers!

				Malcolm.

    I had a heat problem with fuel on my Frogeye until I fitted a
    heat-shield. I got one of a scrap Allegro or Montego, I can't remember
    which. The key was the single HS6 carb, and I recall some of the
    earlier All-Aggros had twin SUs.
    
    It made a difference...
    
    Laurie.

    It makes sense, too... fast cruising builds up engine bay heat, and
    then when you slow down to a crawl it really makes a difference.
    Likewise, general driving at low rpm doesn't build up the heat as much
    (in your case, not until 10-15 minutes). But while you're moving, the
    problem disappears. Or atleast it did with me.
    
    Answer : Stick the ultimate mod to your Sprite - RS Turbo bonnet
    louvres! Cool or wot!?
    
    (I'm joking, I'm joking, I'm not that sad..... ;-) )!!!

    Actually, I did have a real problem with heat on my Frogeye; it turned
    out to be mainly caused by a crap engine (long story, covered in the
    Frogeye topic). In desperation, one option I did consider to help
    improve airflow was to put louvres on the bonnet. I simply couldn't
    bring myself to do it!
    
    Laurie.

	The problem that a lot of cars get isn't so much
	getting air in, it's letting it out.  A lot of kit
	cars suffer heating problems and owners whack on 
	big fans and nothing gets better.  Louvres generally
	work.  Mind you, they haven't got crazy engines with the
	exhaust and inlet manifolds on the same side of the
	engine block.

	Dave (who must really fit a new heat shield to his MG)

    You're absolutely right, no matter how much you can get in, it won't
    make any difference if it cannot get out too. This is why I've avoided
    any fans in my engine bay, and resorted to scoops and extra holes!
    
    Mind you, there was this 1380 Janspeed-turboed Rossa with a severly cut
    up engine bay and one hell of a large fan cooling it all..........
    needless to say, he didn't have much of a boot left. And he mashed his
    gearbox in no time too... ;-)

    re .22
    
    V8 kit cars do have a problem, with exhaust pipes either side of a
    top-mounted carburetter there is a great deal of heat in the carb area.
    The only difference is nobody cares how many louvres are used.
    
    Tony.

    Im back from holidays today and note all the replies since I left....
    
    Yes I do have a heatshield fitted but It does get very hot under the
    bonnet - I'm usign K&N filters which draw their air from closer to the
    exhaust manifold than the originals I feel that this my be my problem.
    
    While on holidays I changed the distributor for a better one
    (there was indeed very slight play in the bearings !!)
    I also fitted a Lucas Sport Coil, + New needles(H6) + jets
    + electronic ignition (Sentronics? + Pirhana sensor)
    The difference in power is at least +10% and everything is running
    and ticking over really smooth, I havent experienced any misfire
    since but then I havent driven the car that much.
    
    The Sprite's electronic revcounter however will not go past 2500 rpm
    since the new setup It's fine on tickover however????
    Ive checked the wiring and everything seems ok?
    
    Cheers
      Brian
    
    
                                                       
     
    
    
    
    
     
    

    Does the electronic ignition have some sort of revlimiter incorporated
    into it - many do. If so, maybe it is badly adjusted.
    
    Is acceleration ->2500rpm no different than before? ie. it whips up to
    it and then just sits there, in any gear, bouncing of the revcounter.
    
    What I'm asking is, does the engine stop revving at 2500 aswell, or are
    we talking just the rev counter - I maybe mis-read the note before
    replying...!

    re -1
    the engine is performing perfectly, It's the rev counter that stops at
    2500, the indicated rpm goes up normally to 2500 and stays there until
    the engine revs go below this again.
    
    The revcounter uses the supply to the coil which passes through a
    loop at the back of the revcounter
    It was functioning perfectly prior to fitting the electronics.
    
    cheers,
    
      Brian
    
    

    Hmmm. Presuming nothing's faulty with speedo, it's the electronic
    ignition is obviosuly doesn't like.
    
    Rev counters work by counting the 'pulses' in the ignition - each one
    is a cylinder firing. You can't just count all the pulses, though,
    since one revolution is made up by 4 bangs (I think). So the electronic
    gadgetry sort of 'divides by 4' to calculate the rpm's. A lot of
    aftermarket rev counters have a switch on the back for 4-6-8 cylinders
    (or more).
    
    Presumeably the electronic ignition stops putting out any more pulses
    when the engine reaches 2500 rpm.     (A pretty pathetic graph with
    revs on X and pulses on Y......)
    
    revs-->------->------->------->
    
                 __<bang!>
                /
               /
              /
             ______cutoff point
            /
           /
    	__/
             |
    	  2500RPM
    
    	This doesn't solve the problem, I know, but I just thought maybe it
    would give somebody with more electronic knowledge a clue...
    
    	P.S. You have wired it up properly ;-)

    re .27
    There are two basic types of rev counter, one is current sensing
    (connected in line to the coil as you described in your car), the other
    is voltage sensing. The problem you are experiencing is a common one
    when fitting electronic ignition to cars fitted with current sensing
    rev counters. I had this problem several years ago with a lumenition
    ignition I fitted to a scimitar. Lumenition offered to convert my rev
    counter to voltage sensing, to cure the problem.
    	A good instrument rebuilder such as richfield should be able to
    convert yours, at a price.
    
    						Andy King. 

    re .29
>>>    There are two basic types of rev counter, one is current sensing
>>>    (connected in line to the coil as you described in your car), the other
>>>    is voltage sensing. 


	What about those Rev. Counters driven by pulses from a pick-up detecting
the passage of magnets (embedded in the Flywheel) going past them?

				Malcolm.

    re .30
    
    That's very useful information, I'll follow up with
    One of the instrument repairers...
    
    
      B.