The importance of points
Discussion
Gents
The Healey was starting to run a bit rough the other day, lumpy tick over, missing a bit at low speed etc, so I thought I would give her a quick once over. Once plugs had been checked and were all good it was off with the distributor cap for points. I noticed straight away the gap had closed up quite a bit, so gave them a light fettle with the points file, reset the gap, rolled the engine over by hand a couple of times, checked and reset the gap until I was happy, then back on with the cap and see if there was any improvement in running.I was amazed at the difference! Now ticks over like a sewing machine, runs cleanly and smoothly at all revs and speeds, like a different car altogether. The point in all this is given the difference between what the points had closed up to and the correct gap, which is only fractions of a millimetre, the impact on the running of the car is phenomenal. At the risk of asking a daft question, why does that minute difference have such a disproportionately large effect on something that is fairly agricultural by today's standards?
Lovely to be able to achieve a great result with a bit of greasy hands work rather than today's cars which require being plugged in to a lap top, then a new "module" of some sort plugging in at great cost by a "technician" in a polo shirt with a corporate logo.
Happy motoring!
The Healey was starting to run a bit rough the other day, lumpy tick over, missing a bit at low speed etc, so I thought I would give her a quick once over. Once plugs had been checked and were all good it was off with the distributor cap for points. I noticed straight away the gap had closed up quite a bit, so gave them a light fettle with the points file, reset the gap, rolled the engine over by hand a couple of times, checked and reset the gap until I was happy, then back on with the cap and see if there was any improvement in running.I was amazed at the difference! Now ticks over like a sewing machine, runs cleanly and smoothly at all revs and speeds, like a different car altogether. The point in all this is given the difference between what the points had closed up to and the correct gap, which is only fractions of a millimetre, the impact on the running of the car is phenomenal. At the risk of asking a daft question, why does that minute difference have such a disproportionately large effect on something that is fairly agricultural by today's standards?
Lovely to be able to achieve a great result with a bit of greasy hands work rather than today's cars which require being plugged in to a lap top, then a new "module" of some sort plugging in at great cost by a "technician" in a polo shirt with a corporate logo.
Happy motoring!
I am no expert in this (my own classic had Lumenition fitted before I bought it, and it remains there today, so no real direct experience with points other than to set up a spare distributor "just in case") but reading up on some other stuff, someone noted that the wrong points gap can alter the ignition timing. I think the specific note was concerning a too-wide points gap, but maybe it works the same when the gap is too small as well.
Someone will be along to explain it properly, I'm sure.
Someone will be along to explain it properly, I'm sure.
Hi,it is always satisfying to sense an engine having been dialled back in by a little work on the distributor.
There are two reasons why the effect of a small points gap is so dramatic; firstly a set of points that are barely opening does not give the ignition coil sufficient charge time to produce a decent spark, you just get a pathetic yellow one instead!
Secondly the distributor runs at half crank speed, so every degree of delay in points opening caused by wear on the heel acting on the lobes of the distributor cam (the usual reason for points closing up)means two degrees of ignition timing retarded at the crank, so with a tiny gap the engine may be firing at or even after top dead centre rather than six or eight degrees before! Makes for a very lacklustre engine indeed!
Hope that makes sense
There are two reasons why the effect of a small points gap is so dramatic; firstly a set of points that are barely opening does not give the ignition coil sufficient charge time to produce a decent spark, you just get a pathetic yellow one instead!
Secondly the distributor runs at half crank speed, so every degree of delay in points opening caused by wear on the heel acting on the lobes of the distributor cam (the usual reason for points closing up)means two degrees of ignition timing retarded at the crank, so with a tiny gap the engine may be firing at or even after top dead centre rather than six or eight degrees before! Makes for a very lacklustre engine indeed!
Hope that makes sense
My car was playing up on the way back from Le Mans a few years back - ran like a dog at idle but got better when you thrashed it. Initially I put it down to crap fuel (started happening soon after refilling) but topping off with better, brand fuel didn't help. Finally died and wouldn't restart when I stopped to enter the code to my underground car park.
When I took a look the next day the points were closed all 360 degrees! It had only been running due to inertia, the cam on the dizzy shaft being enough to 'throw' the points open!
When I took a look the next day the points were closed all 360 degrees! It had only been running due to inertia, the cam on the dizzy shaft being enough to 'throw' the points open!
Russwhitehouse said:
Gents
The Healey was starting to run a bit rough the other day, lumpy tick over, missing a bit at low speed etc, so I thought I would give her a quick once over. Once plugs had been checked and were all good it was off with the distributor cap for points. I noticed straight away the gap had closed up quite a bit, so gave them a light fettle with the points file, reset the gap, rolled the engine over by hand a couple of times, checked and reset the gap until I was happy, then back on with the cap and see if there was any improvement in running.I was amazed at the difference! Now ticks over like a sewing machine, runs cleanly and smoothly at all revs and speeds, like a different car altogether. The point in all this is given the difference between what the points had closed up to and the correct gap, which is only fractions of a millimetre, the impact on the running of the car is phenomenal. At the risk of asking a daft question, why does that minute difference have such a disproportionately large effect on something that is fairly agricultural by today's standards?
Lovely to be able to achieve a great result with a bit of greasy hands work rather than today's cars which require being plugged in to a lap top, then a new "module" of some sort plugging in at great cost by a "technician" in a polo shirt with a corporate logo.
Happy motoring!
It's certainly worth taking some time to dwell on the points you've raised.The Healey was starting to run a bit rough the other day, lumpy tick over, missing a bit at low speed etc, so I thought I would give her a quick once over. Once plugs had been checked and were all good it was off with the distributor cap for points. I noticed straight away the gap had closed up quite a bit, so gave them a light fettle with the points file, reset the gap, rolled the engine over by hand a couple of times, checked and reset the gap until I was happy, then back on with the cap and see if there was any improvement in running.I was amazed at the difference! Now ticks over like a sewing machine, runs cleanly and smoothly at all revs and speeds, like a different car altogether. The point in all this is given the difference between what the points had closed up to and the correct gap, which is only fractions of a millimetre, the impact on the running of the car is phenomenal. At the risk of asking a daft question, why does that minute difference have such a disproportionately large effect on something that is fairly agricultural by today's standards?
Lovely to be able to achieve a great result with a bit of greasy hands work rather than today's cars which require being plugged in to a lap top, then a new "module" of some sort plugging in at great cost by a "technician" in a polo shirt with a corporate logo.
Happy motoring!
Russ,
it's good that you enjoyed adjusting the points as if they're p*ss poorly made modern ones you'll probably have to readjust them again soon
if they're an old set or NOS or from a reliable supplier like the Distributor Doctor it'll just be a matter of checking/cleaning at service intervals for wear (such much per 1,000 miles but can't remember what)
as you can probably tell I'm not a fan and for the last 20 years of using classics as dailies replacing CB points for electronics has been one of the earliest improvements on the various cars (after a full service on them)
in 20 years and into the hundreds of thousands of miles I've never had any problems with electronic ignitions (I've never bought the really cheap ones you can get now) but I have had problems with CB points
as part of the probably worn distributor CB points can be fine but their operation can certainly be improved on with a (good quality and well installed) electronic igniter head just leaving the rest of the worn distributor, I've read that the dissys were out within two to three years of leaving the factory so you can imagine they might be worse after decades so I've got a fully electronic (standard) 123 dissy, it noticeably improved the car's performance throughout the rev range from idle onwards
it's good that you enjoyed adjusting the points as if they're p*ss poorly made modern ones you'll probably have to readjust them again soon
if they're an old set or NOS or from a reliable supplier like the Distributor Doctor it'll just be a matter of checking/cleaning at service intervals for wear (such much per 1,000 miles but can't remember what)
as you can probably tell I'm not a fan and for the last 20 years of using classics as dailies replacing CB points for electronics has been one of the earliest improvements on the various cars (after a full service on them)
in 20 years and into the hundreds of thousands of miles I've never had any problems with electronic ignitions (I've never bought the really cheap ones you can get now) but I have had problems with CB points
as part of the probably worn distributor CB points can be fine but their operation can certainly be improved on with a (good quality and well installed) electronic igniter head just leaving the rest of the worn distributor, I've read that the dissys were out within two to three years of leaving the factory so you can imagine they might be worse after decades so I've got a fully electronic (standard) 123 dissy, it noticeably improved the car's performance throughout the rev range from idle onwards
Hooli said:
Get an electronic ignition system that's playing up & nine times out of ten (in my experience) all you can do is replace it.
buy a decent one install it correctly and it won't play up and possibly last decades without having to fart about with it
Russwhitehouse said:
It sure does explain a lot. Thanks for the interesting reply.
How about this then, after posting about your situation; Made a home visit to a client in Ascot with a rather nice but non-starting Daimler 250V8 on my way home. Owner suspected fuel problem, in fact one set of points closed up!With regard to dodgy points etc, the real challenge seems to be getting reliable condensers without having to resort to generic racing ones
Flatinfourth said:
With regard to dodgy points etc, the real challenge seems to be getting reliable condensers without having to resort to generic racing ones
I was always taught that when replacing worn points, if the condenser was ok then leave it, rather than replace it with a potentially duff one.S1_RS said:
I was always taught that when replacing worn points, if the condenser was ok then leave it, rather than replace it with a potentially duff one.
quite right and even more so with the p*ss poor quality parts you can get todaywhy MGOC Spares includes them in their service kit is beyond me
for reliable dissy parts - Distributor Doctor - http://www.distributordoctor.com/
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