johny

oh that changes everything cos it means your points were open (or a break somewhere) and there wasnt a circuit. Ok well to complete the test you can run a piece of wire from the coil -ve (very important its not the +ve side) to earth to simulate the points being closed and then measure the voltage on coil +ve to earth. Hopefully youll now see ~6v.....

Looks great but whats the verdict? Alright I know it'll need time for everything to bed in.....

hang on with the ignition on you had 12v on coil +ve to earth, 0v coil -ve to earth but 0v coil across the two? That doesnt add up as after the first two readings you should then get 12v across the two terminals....

If you buy a ballast system coil with a resistance of ~1.5 ohms and supply it with 12v continuously it will produce higher sparkplug voltage which will possibly damage high tension components, burn the points excessively and also itself overheat so that I dont think it will run for very long.....

I take it the 0v + to - was without the ignition on? However the 12v and 0v on the coil terminals indicates that something is wrong as a ballasted system should normally only supply ~6v. The only time a ballasted system will supply 12v to the coil is when the starter motor is turning the engine over. So the possibilities are: coil open-circuit (but its 3.5ohmn resistance says no), ballast resistor has been removed or bypassed, contacts on starter motor are permanently closed even when not starting which effectively bypasses the ballast. The fact that you have found a non ballast system coil installed indicates to me that someone has fiddled with this before either as a bodge or intentionally.....

hmmm ok and what volts show on the other terminal of the coil (-ve) to earth - hopefully zero....

ha thats a funny reading! Have you tried the test I described to measure the voltage supply to the coil and end any doubts once and for all about whether your system is modified or not? With that coil resistance I would expect a result of around 9v to earth....

ok if youre certain the system hasnt been modified over the years it should be a ballasted one so you need a 1.5 ohm coil. What was the resistance reading of the old coil across the two terminals with all wires disconnected from them?

oh dear theres still confusion! A 1.5 ohm coil is for a ballasted system and a 3 ohm for a non ballasted set up.... Have you confirmed what your system is?

Looks like normal vapour on a cold day especially as there appears to be a gap between the end of the pipe and the plume which I wouldnt expect if it was smoke....

I read the other day the average annual mileage for classic cars is 900 so its ironic that we worry so much about engine longevity when even a life of only 30k miles equates in many cases to over 30 years motoring🤣

Is it possible to bypass or remove the ballast resistor and so need a 3 ohm coil? I would imagine this is might have been done if the resistor or relay fails so best to check exactly what voltage is being supplied to the coil.....

If you have a ballasted ignition system the coil resistance should be 1.5 ohms and if non ballasted 3 ohms. The coils are not interchangeable. If your not sure which type your system is you could measure the voltage at the coil to confirm it: With the ignition turned on but engine not running measure the voltage to earth at both terminals on the coil. The -ve one going to the distributor points should be zero and the other +ve coming from the supply should show about 6 or 12v with the first indicating a ballasted system (a reading of around 8v would be due to having the wrong coil). If the negative terminal happens to show 12v as well it means the points are open and you need to rotate the engine a little to get them to close. Turn off the ignition while you do this....

If theres no pinking then theres no need to use an octane booster either as an additive or a higher RON fuel in any of our cars. Remember the power available in the fuel isnt changed by its octane level.....

We're going round in circles here: 'unless you want to maintain standard timing and the engine pinks excessively (see test above) in which case you could use an octane booster which might as well include a lead substitute'.....

Brian I really recommend going through the complete sequence of engine adjustments rather than just stabs in the dark. If you do that you then know 100% that those things are right and if theres still problems it narrows down the search and can save a lot of time......

Cant find much info on Dynolite as to exactly what the lead substitute is (not supposed to mix different types) but have noticed that the product with octane booster works out rather more expensive than I thought as its 250ml for only 40L of fuel (25p a litre!). The Millers and Castrol equivalents at around 20 quid to treat 500L are much more economical....

Thats not a bad price although Dynolite wasnt one of the VSR additives approved by FBHVC (however apparently all the various companies invited for testing had to pay for it themselves so some judged it to be uneconomical and declined.....)

yes I think you have to match the petrol octane to the engine compression or even the other way round if, as in some countries, the necessary octane additives arent available. Of course if you have got a higher octane petrol you can run more compression and so make more horses even though the energy content is pretty much the same whatever its octane.....

I imagine if you take the octane too high you might actually be making the mixture more difficult to ignite or certainly changing its combustion characteristics....

If you carry out the test as described you will end up with the correct octane to run your engine with standard timing....

Looking on line it turns out that ethanol is actually an octane booster and the petrol companies now produce a lower octane petrol specifically so that on mixing it with ethanol it gives the correct reading. Of course unfortunately for some engines it can bring other problems.....

I think you might be going overboard a bit. First of all higher octane in itself gives no more power but just allows the engine to run at the correct ignition timing without excessive pinking (pinging, knocking etc). This is optimum if a correctly running engine stops pinking on reaching 2000rpm when under full acceleration in 4th gear on the flat (air temperature will have an effect so best to do the test on the hottest day) and all you need is a fuel/additive that achieves this, any more is unnecessary. Note that valve seat recession is another matter that can occur with or without pinking taking place so other measures may be needed to prevent it.

but its a no brainer if as most people find 95 gives pinking but they want to maintain standard timing then instead of going to 97 use an octane booster + lead additive which works out cheaper per litre fuel and additionally gives the possibility of avoiding VSR. The new concentrated 500L treatment container is convenient to use and although its valve protection is an unknown (it was certified in the tests however) I can confirm the immediate reduction in pinking it gives....

orrrrr use Millers VSPe at 5p a litre of fuel to up 95 to 97ron so that normal running can be maintained while protecting your valve seats and so (hopefully) the jam jar will not be needed.....