The Mallory Unilite dizzy which contains both trigger and coil driver insists you use a ballast resistor - to limit the maximum current. But not really the same as one needed with a 9 volt coil.
A well designed electronic system should have no need of a ballast resistor and 9 volt coil - it should be capable if delivering the correct charge to the coil regardless of normal battery voltage.
Fuel starvation??? 5.0 RV8, Stage 3, eddy carb in a Landy 90
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I was aware that some of their systems use a ballast resistor, personally I think that in this day and age any decent system should not need one, there should be no need to boost the coil for starting purposes, I would avoid any vendor that stated that their system need one!DaveEFI wrote:The Mallory Unilite dizzy which contains both trigger and coil driver insists you use a ballast resistor - to limit the maximum current. But not really the same as one needed with a 9 volt coil.
A well designed electronic system should have no need of a ballast resistor and 9 volt coil - it should be capable if delivering the correct charge to the coil regardless of normal battery voltage.
The OP using using Lucas system, I hope it's not an OPUS one, it ought to be at least the one with the amp on the side or mounted separately near the coil.
If I can risk being a bit blunt here I think that we really need to start being a bit more logical about what's up with this engine.
First of all lets assume that it has been built properly and things like the cam timing and valve to piston clearances are correct, so in other words it is mechanically 'sound'
Right that only leaves two things to check out, the problem has to be either fuel or ignition. You need to work on one or the other until you are absolutely sure that there is nothing wrong with the system that you have checked out. The fault must then be located in the other system.
If you start on the carb then you must check all the obvious things like jetting and fuel delivery to the carb. As your engine won't even rev in neutral I don't think that it is going to be secondary jets or even the fuel delivery. Basically under no load the engine only requires a small amount of air and fuel, probably the transfer slots in the carb can supply enough fuel for this. ( I hope that there is nothing daft going on like the choke flap being shut which will starve the engine of air). The port at the back and front of the carb is not open to fresh air is it?
If you start with the ignition then really you need to be sure that you coil suits your system, an old LD coil could be meant for a points system.
Just what system do you have? 35DML8, DML8 OPUS?
Is your rotor arm a decent one? Real Steel sell some absolute 5hite rotor arms that break down after a couple of hours. Genuine Lucas one are best.
What is your timing set to both at static and all in, when does the 'all in' arrive.
Are you running the vac advance system? if so which port on the carb is it connected to? (I would not even run with the vac advance at all)
Are the HT leads in the right order?
The problem has to lie somewhere in the above gumph!
First of all lets assume that it has been built properly and things like the cam timing and valve to piston clearances are correct, so in other words it is mechanically 'sound'
Right that only leaves two things to check out, the problem has to be either fuel or ignition. You need to work on one or the other until you are absolutely sure that there is nothing wrong with the system that you have checked out. The fault must then be located in the other system.
If you start on the carb then you must check all the obvious things like jetting and fuel delivery to the carb. As your engine won't even rev in neutral I don't think that it is going to be secondary jets or even the fuel delivery. Basically under no load the engine only requires a small amount of air and fuel, probably the transfer slots in the carb can supply enough fuel for this. ( I hope that there is nothing daft going on like the choke flap being shut which will starve the engine of air). The port at the back and front of the carb is not open to fresh air is it?
If you start with the ignition then really you need to be sure that you coil suits your system, an old LD coil could be meant for a points system.
Just what system do you have? 35DML8, DML8 OPUS?
Is your rotor arm a decent one? Real Steel sell some absolute 5hite rotor arms that break down after a couple of hours. Genuine Lucas one are best.
What is your timing set to both at static and all in, when does the 'all in' arrive.
Are you running the vac advance system? if so which port on the carb is it connected to? (I would not even run with the vac advance at all)
Are the HT leads in the right order?
The problem has to lie somewhere in the above gumph!
Ok, i appreciate your approach:-) And perhaps I have been poor in artivulating my problem.
1) fueling is sound - on the open road i can rev clearly with great pull (even with 35 inch tyres) but only to 3000 revs hitting 70mph in 5th when it starts. Now after re-jetting the AFR readings are 14.3 at tickover, 12.8 at cruse and 11.8 at WOT, but readings go haywire when what sounds like fluffy missfire occurs at 3000 revs. Adapted my vaccum gauge (which shows good readings) to measure the post regulator fuel pressure (4.8 PSI constant).
2) the engine sounds very smooth at tickover, valve timing set on roller chain when assembled. Tappet clearances were satisfactory. And sound great right up to the point of the dreaded 3000ish mark were the fluffy missfire occurs. I suppose valve timing could be a problem but I doubt it would be so focal in its effect.
3) used timing light to set up ignition, but markings are not correct, as when set there was far too much advance and pinked under load. I have experimented and gone all the way from here turning the dizzy ever so slowly - improving and improving but never breaking that sealing.
So this led me to think - (like you) - if the engine is assumed sound - and it is not fuel (which it is not) then it must be ignition - so then i thought right - if it is ignition then I have 2 choices a) begin by working my way through component parts ( coil +/- adding resistor (it is a 12v coil off a series 3 land rover v8 circa 1981)(new pattern part) - which is something i am strongly thinking of doing - OR bearing in mind I want to run NOS and change maps on the fly etc, and I have heard (as from yourself) that programmable systems have other benefits should I just not bother spending money on an ignition system I would ditch eventually anyway.
The advice I am asking from you guys is - if you were me would you go on a component search and were would you start considering my symptoms - or would you treat yourselves - I am not made of money but not absolutely skint either.
If I apply a dizzyless ignition and it fails to cure the problem - then I will take a deep breath and need to review a time consuming engine metalwork mistake.......
Sorry if i was a bit scatty previously
thanks guys
Dave
1) fueling is sound - on the open road i can rev clearly with great pull (even with 35 inch tyres) but only to 3000 revs hitting 70mph in 5th when it starts. Now after re-jetting the AFR readings are 14.3 at tickover, 12.8 at cruse and 11.8 at WOT, but readings go haywire when what sounds like fluffy missfire occurs at 3000 revs. Adapted my vaccum gauge (which shows good readings) to measure the post regulator fuel pressure (4.8 PSI constant).
2) the engine sounds very smooth at tickover, valve timing set on roller chain when assembled. Tappet clearances were satisfactory. And sound great right up to the point of the dreaded 3000ish mark were the fluffy missfire occurs. I suppose valve timing could be a problem but I doubt it would be so focal in its effect.
3) used timing light to set up ignition, but markings are not correct, as when set there was far too much advance and pinked under load. I have experimented and gone all the way from here turning the dizzy ever so slowly - improving and improving but never breaking that sealing.
So this led me to think - (like you) - if the engine is assumed sound - and it is not fuel (which it is not) then it must be ignition - so then i thought right - if it is ignition then I have 2 choices a) begin by working my way through component parts ( coil +/- adding resistor (it is a 12v coil off a series 3 land rover v8 circa 1981)(new pattern part) - which is something i am strongly thinking of doing - OR bearing in mind I want to run NOS and change maps on the fly etc, and I have heard (as from yourself) that programmable systems have other benefits should I just not bother spending money on an ignition system I would ditch eventually anyway.
The advice I am asking from you guys is - if you were me would you go on a component search and were would you start considering my symptoms - or would you treat yourselves - I am not made of money but not absolutely skint either.
If I apply a dizzyless ignition and it fails to cure the problem - then I will take a deep breath and need to review a time consuming engine metalwork mistake.......
Sorry if i was a bit scatty previously
thanks guys
Dave
Spent so much on trial and error!
DaviesDJ wrote:Ok, i appreciate your approach:-) And perhaps I have been poor in artivulating my problem.
1) fueling is sound - on the open road i can rev clearly with great pull (even with 35 inch tyres) but only to 3000 revs hitting 70mph in 5th when it starts. Now after re-jetting the AFR readings are 14.3 at tickover, 12.8 at cruse and 11.8 at WOT, but readings go haywire when what sounds like fluffy missfire occurs at 3000 revs. Adapted my vaccum gauge (which shows good readings) to measure the post regulator fuel pressure (4.8 PSI constant).
2) the engine sounds very smooth at tickover, valve timing set on roller chain when assembled. Tappet clearances were satisfactory. And sound great right up to the point of the dreaded 3000ish mark were the fluffy missfire occurs. I suppose valve timing could be a problem but I doubt it would be so focal in its effect.
3) used timing light to set up ignition, but markings are not correct, as when set there was far too much advance and pinked under load. I have experimented and gone all the way from here turning the dizzy ever so slowly - improving and improving but never breaking that sealing.
So this led me to think - (like you) - if the engine is assumed sound - and it is not fuel (which it is not) then it must be ignition - so then i thought right - if it is ignition then I have 2 choices a) begin by working my way through component parts ( coil +/- adding resistor (it is a 12v coil off a series 3 land rover v8 circa 1981)(new pattern part) - which is something i am strongly thinking of doing - OR bearing in mind I want to run NOS and change maps on the fly etc, and I have heard (as from yourself) that programmable systems have other benefits should I just not bother spending money on an ignition system I would ditch eventually anyway.
The advice I am asking from you guys is - if you were me would you go on a component search and were would you start considering my symptoms - or would you treat yourselves - I am not made of money but not absolutely skint either.
If I apply a dizzyless ignition and it fails to cure the problem - then I will take a deep breath and need to review a time consuming engine metalwork mistake.......
Sorry if i was a bit scatty previously
thanks guys
Dave
Hi Dave,
Its a tricky one really, if you are pretty sure that your ignition is duff and you want to replace it anyway then it is tempting to say what's the point in spending money on your old system.
Just one thing though, the post regulator PSI is not quite the same as the post PSI fuel flow. (Having said that I guess the pressure would drop is the fuel demand out stripped the supply capacity). I think that 4.8 PSI is a bit low, 6.5 would better but I guess its OK.
The MSD system does use a distributor which some will say is not that great but it can be used to just distribute the HT so its doing very little, the actual timing can be controlled by a crank trigger system if you wish.
Having a single coil is no problem because the time does not depend on the coil, the capacitor in the MSD can charge much quicker than a coil.
The MSD systems that I have setup have used a trigger in the actual Lucas dizzy. The dizzies were locked out so that the timing curve is totally programed into the actual MSD unit. One good thing about my setup is that it just looks totally standard but really its running a system that is quite sophisticated with multiple sparks per plug below 3k RPM, there is enough HT to kill you if you disrespect it!
Cheers,
Pete
Hi Guys - well, megajolt now fitted and mapped with standard map - Am pleased to say it revs brilliantly now!!! Problem well and truly solved - my hunch is that I had a poor amplifier setup and a weak spark was being generated! Now going better than ever, only clutch slip letting me down now - thanks for all your help - but good to note all this as a learning point, weak spark with RPI amp
Spent so much on trial and error!
