Lucas 25D max lead resistance
Discussion
That's a curious question. Do you just have some leads with what you consider to be an unusually high resistance or are you actually wanting to run higher than normal resistance for some unfathomable reason?
Usually the resistance of silicone HT leads is at most a couple of kilo ohms per foot. I'm not sure what the distributer type has to do with any of it. The resistance is primarily there for RF suppression and within limits has very little to do with the spark strength, bhp output or any other operating function of the engine. You can't make the engine run better with either higher or lower resistance leads than stock despite the claims of some HT lead manufacturers.
Usually the resistance of silicone HT leads is at most a couple of kilo ohms per foot. I'm not sure what the distributer type has to do with any of it. The resistance is primarily there for RF suppression and within limits has very little to do with the spark strength, bhp output or any other operating function of the engine. You can't make the engine run better with either higher or lower resistance leads than stock despite the claims of some HT lead manufacturers.
camelotr said:
Hi Pumaracing, nice to meet again 
!
My question was due to I have installed some nice period Champion spark plug caps, and experienced missfire at low revs. I think the caps are resistor types to help filltering for the radio. They are rated 10Kohms.
10 Kohms is a bit extreme. Have you actually measured them on a multimeter? Are the plugs also resistor type because in conjunction with such caps and the leads the total resistance could be far too high. !My question was due to I have installed some nice period Champion spark plug caps, and experienced missfire at low revs. I think the caps are resistor types to help filltering for the radio. They are rated 10Kohms.
You can possibly take them apart and remove the resistors and replace them with bits of copper the same length - or just go back to your previous caps.
camelotr said:
The 10Kohm is printed on them. I have failed to measure their resistance with my gauge. I think the 9Vs is just not enough to go through them.
Of course it is. Any ohm meter will measure them if you are making proper connections. Sounds like they might be buggered and gone open circuit.They might be, but I have a suspicion that some old-style plug caps have a spark gap in them. I've never taken one apart to check, but I have occasionally failed to be able to measure continuity through them (engine running fine, just doing it for the crack 
) - and I do know what I'm doing with an ohmmeter
I do hate that crappy carbon string HT lead stuff though. The way it deteriorates and causes obscure faults which lead people to replace everything in sight without result, then after wasting lots of money finally sort it by replacing the HT leads - plenty of threads in this forum containing such tales - and there's just no bloody point to the stuff. It's cheap-arsed s
t which causes problems for no benefit.
More relevantly to this discussion, it's difficult to terminate especially in fittings designed for the proper copper stuff. It may well be that neither the distributor-end terminations nor the plug caps are making a decent connection to it.
I'd be inclined to start again - bin the carbon string stuff, and replace with decent copper cored cable as per the original; replace the state-of-unknown-dodginess plug caps with new, non-resistor ones - thereby eliminating another possible point of failure - you can still get them new; and use resistor plugs if you find you need the resistance for suppression - I think for that engine NGK BPR6ES are the ones. Then you will know that everything downstream of the distributor is as sound as it can be and likely to remain that way, and if you still have problems it's something else that's wrong.
) - and I do know what I'm doing with an ohmmeter I do hate that crappy carbon string HT lead stuff though. The way it deteriorates and causes obscure faults which lead people to replace everything in sight without result, then after wasting lots of money finally sort it by replacing the HT leads - plenty of threads in this forum containing such tales - and there's just no bloody point to the stuff. It's cheap-arsed s
t which causes problems for no benefit.More relevantly to this discussion, it's difficult to terminate especially in fittings designed for the proper copper stuff. It may well be that neither the distributor-end terminations nor the plug caps are making a decent connection to it.
I'd be inclined to start again - bin the carbon string stuff, and replace with decent copper cored cable as per the original; replace the state-of-unknown-dodginess plug caps with new, non-resistor ones - thereby eliminating another possible point of failure - you can still get them new; and use resistor plugs if you find you need the resistance for suppression - I think for that engine NGK BPR6ES are the ones. Then you will know that everything downstream of the distributor is as sound as it can be and likely to remain that way, and if you still have problems it's something else that's wrong.
Mona Lisa should be hang on a rusty nail?
After selling this car, I will see a deficit of zillion pounds. Does it matter if I top it a bit with making the car looking better?...
By the way, the machinist now thinks that I am a cheater, and he told me that I am lying.
Muhahah!...
As we hungarians say, the Zoo of God is very big...
After selling this car, I will see a deficit of zillion pounds. Does it matter if I top it a bit with making the car looking better?...
By the way, the machinist now thinks that I am a cheater, and he told me that I am lying.
Muhahah!...
As we hungarians say, the Zoo of God is very big...
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