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  1. #11
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    593
    use a vacuum gauge, it will tell you want timing your engine wants using that fuel. You can check the coil with a multimeter, simple to do with loads of info on youtube
    Paul, two things worth considering. Firstly fuel. There can be quite a bit of variation especially with supermarket fuel. Might be worth waiting until your empty then putting some better quality stuff in like Shell VPower to see if things improve, especially the running on. Secondly, the electronic ignition system. I had a similar problem last year with my Pertronix which caused poor pick up in higher gear which I suspected to be the coil. Once replaced back to normal! As has been said I would be reluctant to go altering a rolling road set up unless you’re sure the dizzy has slipped. Hope you soon get it sorted.
    Dek
    Thanks Dek ,Paul ,and yes agreed , a vacuum gauge would come in very useful . Alan also advocates me fitting one, so i will definitely stick that on my "to do list". Not sure whether to mount it with the other gauges or stick it in the engine bay.

    Found HEI 8392 on my dizzy, then found the paperwork from Paul ,the previous owner, and now know that i have an MSD Streetfire HEI 8392 dizzy, so using Utube as Paul suggested, i have just checked the coil and fairly sure i have found it faulty,so thanks for the suggestion Dek

    Primary should be reading below one ohm ,and it,s reading 0.7 ohms ,so ok .......but the secondary should read between 30,000 and 60,000 ohms, and is actually reading open circuit. Surely that reading means the coil is totally buggered ,but if that is the case ,i don,t understand how the engine is even starting ,let alone getting me down the road.

    Anyone answer that for me please.

    So does anyone know if i can just order the coil for my dizzy or do i have to buy the whole dizzy, i bl--dy hope not !

    whats annoying is ,the damn thing has only done 7000 + miles ,which is pretty poor in my opinion
    Last edited by psh; 06-04-19 at 02:38 PM.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  2. #12
    Join Date
    Mar 2008
    Location
    Coventry
    Posts
    2,308
    Paul,

    my coil failed on mine after only 2000 miles, same one as you. Stateside on the A5 sell them and usually have them in stock. Give them a ring to check Tuesday as they are closed on Monday

    Paul
    AK, on the road Oct 2012

  3. #13
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    593
    Quote Originally Posted by seph View Post
    Paul,

    my coil failed on mine after only 2000 miles, same one as you. Stateside on the A5 sell them and usually have them in stock. Give them a ring to check Tuesday as they are closed on Monday

    Paul
    Thanks Paul, i will give them a call. Sound s like i can replace just the coil,hopefully they are not too expensive.

    Do you know how my engine is even running ,with the secondary reading open circuit, i would have thought it wouldn't even produce a spark........baffled ?
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  4. #14
    Join Date
    Mar 2008
    Location
    Coventry
    Posts
    2,308
    Quote Originally Posted by psh View Post
    Thanks Paul, i will give them a call. Sound s like i can replace just the coil,hopefully they are not too expensive.

    Do you know how my engine is even running ,with the secondary reading open circuit, i would have thought it wouldn't even produce a spark........baffled ?
    Mine was faulty and still running the car although poorly, so i have no idea. I think mine was about £30
    AK, on the road Oct 2012

  5. #15
    Join Date
    Mar 2006
    Location
    Oxfordshire
    Age
    68
    Posts
    1,631
    Paul,

    I'm not familiar with the MSD HEI dizzy, but if the coil is wound the same as the GM one then there are two measurements you need to take for the secondary winding resistance check, and it's apparently OK for one of them to be open circuit. Google HEI distributor coil test and you'll find further info.

    As per our discussions, the "running on" issue is in my opinion likely to be overadvanced timing at idle - possibly due to the vacuum advance. If it's connected to the full/untimed (below the throttle plate) port, try moving it to the timed port and see if this makes a difference. As per my voicemail you need to find the score mark on the harmonic balancer and highlight it with white paint or Tippex so you can see it with the timing light. You can then check the timing and see how it advances and retards. It may also help to fit slightly colder plugs.

    As your car has been laid up over the winter, my first suspect for the rough running issue would be a blocked fuel jet (probably on the secondary side as these are less frequently used and therefore more susceptible to gumming up) or fuel passage - possibly the power valve channel restrictors. Both of these would cause stumbles on hard acceleration. So it's worth removing the fuel bowls and metering plates/blocks and spraying liberally with carb cleaner and compressed air - make sure you have some new bowl and metering block gaskets though in case the existing ones tear when removed.

    Personally I wouldn't worry about the coil at the moment - as you say, if the secondary is truly open circuit then the engine wouldn't run at all! Also, when you have two separate symptoms, it's best to solve one and then move to on the other - otherwise you're likely to get confused!
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club (eurocobra.boards.net)
    Dax 427 DeDion - Huddart SBC 383

  6. #16
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    593
    I'm not familiar with the MSD HEI dizzy, but if the coil is wound the same as the GM one then there are two measurements you need to take for the secondary winding resistance check, and it's apparently OK for one of them to be open circuit. Google HEI distributor coil test and you'll find further info.
    The first web site i found yesterday explaining how to test the coil on a MSD HEI street fire dizzy coil ,had diagrams and advised to check the primary by putting test probes across the “tach/red” and “Bat/yellow ” terminals = 0.7 ohm. Then it advised to check the secondary with probes across the rotor button and “bat” terminal , which according to the diagram was the carbon protruding button inside the dizzy cap and the “bat”/red terminal . The “Bat” and “Tach” are marked on the top of the cover ,covering the coil unit.

    However ,the next web site I found today advised the same terminals to test the primary, but to test the secondary ,with probes across the same rotor button , but instead on the black centre wire with the eyelet terminal instead ,which gave 6850 ohms,which according to info on the web is within tolerance, meaning the coil is ok. So I don’t know which site to believe now .

    So I would be very interested to know exactly which terminals i should be measuring across .

    As my symptoms match exactly what a duff coil would produce , I am going to just buy a new coil and stick that in to see if it cures the issue and if not i will reluctantly do as you suggest Alan and tear down the carb, which I am not confident to do ,because i have never touched a holley carb before or any carb, apart from an SU on my old mini.. Do i need special tools to extract all those bits you mentioned ?
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  7. #17
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    1,573
    That sounds like a good approach Paul and for the relatively small cost of a coil you’ve got a spare coil in your boot in the event of complete failure if it doesn’t cure your problem. I’m by no means an electronics expert but common sense dictates there is something in between a coil that is working 100% and a coil that is dead. Can a simple test meter detect this? I don’t know. These high energy coils kick out up to 60,000v. Certainly the Pertronix can. What if they are producing less but enough to run a big V8 comfortably but not optimally? It would cost more to put on a rolling road for a full diagnostic check with all the inconvenience of getting it there. Go for it!
    Dek

  8. #18
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    593
    I have not had much time to work on the cobra since my last post, due to all my spare time being used up sorting out on-going issues in the care home my mum is now in and clearing her house of furniture, ornaments, etc. and preparing it for sale. However, Denis very kindly lent me a brand new coil to see if that cured the problem, and it didn’t, so I know my coil is not to blame. All the old fuel has been replaced with non-super market fuel. Next thing I did was to remove all the plug leads to check them out properly, and I discovered two of them were badly fried, just next to the spark plug boots, which get the most heat from the manifolds, and then discovered those particular fried leads were open circuit, because the inner conductor had actually snapped clean through. I thought FANATASTIC! ,I have found the fault, and ordered a set of high performance plug leads as recommended by Alan, and have just fitted them ,using DEI high temp protective sleeving and re-routing the leads down and under the manifold ,so these don’t get fried ……and BL—DY H-LL, it’s still not running right !!!! .

    With the new leads fitted, initially the engine took its time to start, and once the electric choke had wound itself open ( on my list to swap for a manual choke, which is on a shelf in my shed), once it warmed up, it seemed to tick over more steady and smoother than before .When hot, it always starts almost instantly and pulls off reasonably well when I gradually depress the throttle , and on the open road it pulled smoothly and with reasonable oomph right up to 60mph ,but when I stab the throttle to the floor , it hesitated again and misfired ,and only pulls about 80% , not like it used to .

    With engine hot and ticking over, if I blip the throttle gradually , the revs pick up reasonably well, but not as cleanly as it should , but while ticking over ,if I stab the throttle half way down to the floor, it bogs, misfires, slight whiff of petrol, and the engine dies ,every time !

    My big dilemma is , my wife and I were planning on taking the cobra on a 200 mile trip up to Whitby In Yorkshire tomorrow ,travelling around for three days ,then heading back on Tuesday. My question is , if I drive my cobra gently ,could I do any damage to the engine/carb etc, or should I play safe and go in the tin top.

    I know the next thing I should replace are the plugs ,then look at is the carb and timing ,but I just don’t have the time right now, so on recommendation ,I was thinking of taking the cobra to Vince Gibbs near me in Banbury ,who specialises in Holley carbs and tuning American SBC V8’s ,as well as classic car restoration .
    Last edited by psh; 24-05-19 at 01:29 PM.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  9. #19
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    593
    As you know ,way back in May ,I was trying to find out why my AK was misfiring ,hesitating badly , and running on, and fitting new leads and swapping the dizzy cap for a known good one ,which was loaned to me , didn’t cure the problem .




    So as I just didn’t have time to carry on fault finding, on recommendation I took it to a guy called Vince Gibbs in Banbury near me , who runs a classic car restoration/Engineering company ,and who also owns a Southern Road craft cobra with the same engine and carb as mine, perfect I thought . Like Alan he first thought it was carb related ,so he stripped it ,checked the power valve diaphragm , float levels , accelerator pump ,jets and metering plates ,all clear , no gumming found, replaced all gaskets , carb all good. He then turned his attention to the dizzy, and to save time he swapped my dizzy for the one in his cobra, and straight away, the fault was gone. So he put mine back and discovered that when he blipped the engine, now and again the timing was wandering back and forth, and discovered this was down to the rotating magnetic pick-up disc which should be crimped solidly to the main shaft, being slightly loose and was intermittently slipping. He managed to cheaply get hold of brand new inners, using contacts he made during his drag racing days. It was a completely different car to drive afterwards, firers up instantly, hot or cold, no more misfiring or hesitating, or trying to stall at junctions and wow, it’s a completely different car to drive now and boy does it pull now.

    Vince is a really knowledgeable resourceful guy, who works on his own and takes pride in his work and his hourly rate is reasonable. Vince's extensive engineering knowledge and problem solving skills, results in a high quality of workmanship. For many years he has worked on all sorts of classic and performance cars, and was working on a beautiful “E” type Jag when I first met him. His previous job was in the alloy sheet metal industry, and he is very knowledgeable and experienced on the subject, and more importantly knows how to weld the stuff. So while he had the cobra ,I asked him to design ,fabricate and fit an alloy bespoke sump guard ,which had to be light weight ,strong and protect both the front and rear of the sump . So Vince fabricated and fitted a prototype sump guard made from sheet mild steel, to make sure there was no problems with his design, before making the finished product out of 3mm, 6082-T6 alloy. Fitting the guard has only decreased the ground clearance by about 10 mm. On my suggestion he incorporated air intake slots at the front, high enough up the sloping front face, so as to not catch on anything, and louvres down each side to allow air to flow past the sump and starter motor. So as to not weaken the chassis by drilling all the way through the box section, he has used M6 bolts and rivnuts to secure the guard.




    As the sump guard completely shrouds the sump from all sides, which makes it extremely strong, it blocks a lot of air flow to the sump, so I got Vince to fit a thermostat controlled oil cooler.



    He has also cured my “slow cranking when hot issue”, by fitting a mini high torque geared Tilton starter motor ,and bl—dy hell does it spin the engine over , even on a boiling hot day .

    He has also modified the steering column mountings and moved the steering wheel as far away from me as possible, so it’s now a much more comfortable diving position.

    I also asked him to repair a bit of damage to the rear end, which involved repairing some of the glass fibre and a respray.

    Even though Vince has seriously decreased my “to do “ list of jobs , hopefully next year I will have time to wrap the exhaust manifolds, fit some decent horns, swap the electric choke for a manual , calibrate the fuel gauge, and , probably something else 

    I made the right decision to give the cobra to Vince , as he rattled through all these jobs , and i soon had the car back, giving my Wife and I chance to go out and enjoy the cobra during the summer , as well as giving me time to continue repairing and clearing out my mother’s house , who sadly passed away in August.

    If anyone needs any work doing on their cobra, I can thoroughly recommend Vince and this is a link to his Facebook page https://en-gb.facebook.com/vincegibbsclassiccars/
    Last edited by psh; 21-10-19 at 11:45 AM.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

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