Classic cars forum & vehicle restoration.

[Ray White]

[quote="MikeEdwards"
....I'll adjust the gap to get the correct dwell (rather than adjusting it to get the correct gap) and see if it's any better.[/quote]

This is something that I have never quite understood. Every manufacturer states the required points gap but hardly ever mentions dwell. Different results presumably means one is right but which is it?

[MikeEdwards]

[peter scott]

Perhaps I'm being thick but surely the points gap is the only simple adjustment of dwell. If you wanted to change the relationship between gap and dwell then you would need to change the profile of the cam.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[Ray White]

I always thought that if you left the points in until a pip had developed then they had been left for too long... or there was a faulty condenser. I was always encouraged to replace the points and condenser at the same time. Unfortunately, these days, the quality of the parts is variable. Electronic ignition is probably the way to go now.

[MikeEdwards]

[MikeEdwards]

I test drove the car today again, after setting the points so that I had a dwell angle of 36 degrees (the manual says 35-37, so I'll take that), shows that it is much better than it was on Sunday when I last drove it. I have also changed the plugs back to the older ones, and reset the timing (which was essential after the points change), so perhaps the combination has helped.

I wonder if this will make it easier to start - I could imagine that not energising the coil for long enough won't help it cold starting.
_________________
1976 Vauxhall HP Firenza, 1976 Vauxhall Sportshatch (x2), 1986 Audi coupe quattro, 2000 Audi TT

[Penman]

Mike: I have just had a thought about this, which may or may not apply to your vehicles.
I had a couple of Vivas (HB and HC) and I'm sure they had one of those thing-emee-bobs attached to the LT side of the coil which supplied 12 Volts for starting and less for running.
I remember having problems with them.
_________________
Bristols should always come in pairs.

Any 2 from:-
Straight 6
V8 V10

[ukdave2002]

[MikeEdwards]

You are quite correct, in standard form it would have this. One of the issues is that my starter motor is not from a Vauxhall as they're relatively difficult to get, so it doesn't have the by-pass circuit on it. Initially I'd rigged something up with a diode connected to the starting circuit, and I must confess I can't quite remember what I've done now. I know on the Firenza I by-passed the loom resistance section and put a separate ballast resistor alongside the coil, but I don't remember on the hatch - I think I put a non-ballast coil on it. I'll have a look later - I know I took the diode connection off a while back.

I by-passed it on the Firenza because a previous owner had caused some damage to the loom behind the dash (I think it was on the dash lighting circuit) and when I took it out to repair it, I just wasn't happy with the condition of it. I couldn't quite decide whether it should get warm, and even if it should (what with the energy having to go somewhere) I don't really like warm wiring. So I used a standard ballast resistor mounted on the coil which is on top of the inlet manifold, where it's always warm anyway.
_________________
1976 Vauxhall HP Firenza, 1976 Vauxhall Sportshatch (x2), 1986 Audi coupe quattro, 2000 Audi TT

[ukdave2002]

Regarding setting the dwell v setting the points gap, it's the dwell that's important but as Mike points out back when points systems were normal , dwell meters were very expensive and as dwell is directly governed by the points gap, setting the points is perfectly fine. If the gap is correctly set and the dwell is incorrect there has to be a problem in the distributor, normally wear.
Also remember that if the points gap is altered so will the ignition timing, this frequently isn't checked when the gap is adjusted.

Regarding the comment that one could fit electronic ignition and forget about the condenser isn't strictly correct as the condenser will now be built in to the electronic ignition unit, without the condenser the primary voltage would take longer to drop to zero when the transistor switch's the current off, resulting in a lower HT voltage.

Condensers in Electronic ignition systems can and do fail, sometimes you can get at them to replace, other times you have to add an external one, that said the capacitors in Electronic ignition systems tend to be more robust than the ones supplied to fit in distributors.

Dave

[ukdave2002]

[MikeEdwards]

[V8 Nutter]

Recently I felt the Cadillac was not running quite as it should. First thing was check the plugs, they were all O.K. Next was check the dwell it was about three degrees out. I re-set that and everything was back to normal. On the Cadillac it is easy to set the dwell the distributor cap has a little window where you insert an allen key and adjust the dwell with the engine running. The shop manual gives a point gap but suggests that is only an initial setting, final setting should be with a dwell meter. On the subject of HB and HC Vivas they were notorious for points and condenser failures. I am fairly sure they had two wires to the coil, one was a resistor wire for normal running and a non resistor for starting. The change over was controlled by the ignition switch.

[MikeEdwards]

[alastairq]

Renault 14s had an external dwell adjustment feature too.
I had one 40 years ago, and found the dwell adjustment very useful. Especially when compared to other methods, which involved a process of hit n miss, tweeking of the points gaps, which often resulted in a little too much, or a bit too little!

I often used to check pints gap on all the lobes, frequently finding variations.

Not significant one's , but variations all the same.
Even variations between hot, and cold!
Which is why I now always look at replacing points with a Hall Effect set-up.

When trying to tune an engine to get the best out of what I had got [so to speak], then tiny tweeks here and there were important....especially when playing with low horsepower outputs.

I competed in Reliability Trials for quite a while, using rear engined Skodas..which also had the resistances screwed onto the coil....
If changing to a full 12 volt coil, then I'd literally join the two ignition wires together....I'd also solder up solid the pilot jet fuel cut-off valve and disconnect [and hide securely] the solenoid wire...thus eliminating any chance of the wire disconnecting on a section, and bringing the whole caboodle to a rapid halt?

I was never very happy about having a live 12 volt feed wire plugged directly to the carburettor, on any car!
If I encountered any dieseling, I was happy to hold the brake down and release the clutch in gear to stop the engine running-on. Not that it happened very often in my hands anyway.

Another aspect of mechanical points I noticed, once I'd got myself a strobe timing light [decades ago, still got it]...was that, when looking for 'full advance', how much the timing marks jolted around, even though the revs were constant.
This was to be expected given the points had a spring steel component. A tiny bit of wear in the distributor shaft probably wouldn't help either [not enough to force replacement, but not brand new either]
Once a Skoda electronic distributor from a Favorit was fitted, the timing marks stayed remarkably steady at full advance! The skoda estelle/rapid rally boys even produced a solid state ignition module which overcame the Favorit's trick of packing in at awkward moments...this due to the Favorit being front engined, the module was kept cool by air flow...but in the rear engined position, the heat was too much for it....I tried computer fans stuck on the outside for a while, until I could afford the 25 quids to buy the solid state module from the owners club...
In an attempt to get cool air into the engine bay, I even bolted a Nissan [purely by chance] electric radiator fan into the right side rear wing, drawing outside air from various holes located there[by my drill]...
I would use this when queuing for a section, and in section....every bit of horsepower counted when limited by engine capacity.

I didn't run it all the time, as two rad fans up front, plus the Nissan one, all going at the same time, was a bit too much for the alternator's output....so I would switch it out once the 'section ends' board was seen. Otherwise an eventual flat battery was the result.

I never really suffered the dreaded skoda head gasket trouble after that, either.
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.