Morris Minor Owners Club

Hi, I am a bit confused, as I have purchased a engine analyser with the dwell angle check, and after setting the points to 15 thou I am getting a 40 degree dwell angle... Its a new accuspark distributor, and with the previous setting which I measured at 25thou I had a 30 degree dwell and the car idled more linear.... What am missing? The car is a minor 1000 1970.
Thank you.

The points gap and dwell angle are directly related so by varying the points gap you can achieve the desired dwell angle.
The points should be set to 0,015" but as you have a dwell meter forget about manually setting the points gap and set the points by using the dwell angle. The dwell angle should be set to 60 degrees plus or minus 3 degrees which is the factory specified setting for the 1098cc engine.

The dwell meter setting of 60 degrees will compensate for any variance of the 0.015" points gap (not all perceived 0.015 point gaps are 0.015") and any wear in the distributer - as the distributer is new there should not be any variance due to wear.

I would prefer to rely on the dwell meter to set the points gap than a 0.015" feeler gauge blade.

Did you adjust the timing, after changing the contact point gap?

The dwell angle is simply the means to reach (near) saturation current in the coil at maximum engine speed.

There are two requirements for the points when opening. First it must be fast enough to avoid sparking as the points open - this is determined by the cam profile. Coil voltages achieved are dependent on the rate at which the magnetic flux changes. Secondly, the points must open sufficiently to avoid any increased voltage oscillations at the live point arcing across and reducing the spark energy.

Too small and the contacts will burn away at less than the service interval for points change, or the points could fail prematurely.

Thank you for your replies!
Yes Oliver I have set the timing afterwards, but my idle isn't as linear as before the rebuild, and the mark varies between 2.5 and 5 degrees.


After spending about 30 min, with a feeler gauge, I was only able to achieve a 45 degree on the dwell machine. Also I have the option to check the points on the analyser and I had a resistance of 1ohm and it displayed as bad, apparently it needs to be under 0.5. "Luckily" I have 3 contact points, 3 rotors and 3 condensers all of them for the 25d distributor which I no longer use due to the vacuum pump giving the ghost. No chance to get these parts in Romania, so just placed an order with esm, with a bit of luck I will receive the items this year .

Am I right in assuming that a Set of points with higher resistance won't affect the dwell angle?Also can the dwell angle be measured without starting the engine? Sorry if it's s a silly question.

Thank you all for taking the time.

Slownsteady wrote: ↑Tue Sep 01, 2020 10:09 am
After spending about 30 min, with a feeler gauge, I was only able to achieve a 45 degree on the dwell machine.

Why are you wasting time with a feeler gauge?
The whole point of using a Dwell meter is to set the gap using it, not to spend 30 minutes with the feeler gauge and then not have the right Dwell.
Phil clearly said yesterday:

as you have a dwell meter forget about manually setting the points gap and set the points by using the dwell angle.

if you have a high resistance set of points, clean them. They're high resistance because dirty or pitted.
Don't attack them with sandpaper, use an Electrical contact/points file, if you can find one, they're getting hard to find these days. A result of our throwaway culture. If you search ebay, most seem to come up from USA or Australia.

You don't seem to understand what you're doing with the Dwell meter and perhaps not understanding the advice you've had so far.

Perhaps reading this might help you understand:
www.howacarworks.com/ignition-system/ch ... well-angle

it also answers your question

can the dwell angle be measured without starting the engine?

Hope that helps.

Hi geoberni, thank you for the scolding

It s the first time I am using the engine analyser, and the first time I am measuring the dwell angle. I have read that article in your link some time ago but I was assuming that I would still require the feelers to get it to a correct setting. I will just try to open the points as much as needed to obtain the 60 degrees reading, and report back.
Unfortunately I only have some small diamond files for cleaning the points. Would those be OK, as i am also unable to find specific points file in Romania.
Thanks.

Not a scolding, just trying to ensure you understand what's occurring.

A small diamond file should do the job. Contact points should be hard, and usually made of something like Tungsten Steel so a regular file is no good, nor the likes of sandpaper.
The problem these days is that even on an industrial basis, contacts aren't often reworked; if a quick spray with some cleaner fluid doesn't work, they replace the larger assembly.

As regards an ignition/points file & just so everyone knows what we are talking about.
https://www.ebay.co.uk/itm/IGNITION-POI ... SwiwZcNGOq

Reviving an old thread but it may be relevant to anybody who finds this thread by searching.

I was reading the instructions for the Gunson Supastrobe G4123 as I am considering buying one (I do not like my nasty Accuspark strobe). The Gunson Supastrobe gives a dwell reading in per cent not angle. A 60 degree dwell angle on a 4 cylinder engine is 66.666% BUT the Gunson instructions say that if their strobe is used on a POSITIVE earth vehicle then the displayed dwell per cent should be taken away from 100 to get the dwell percentage. So in this case the dwell meter would read 33.333 %. This happens to be very close to the figure that the OP said gave good running. I wonder whether that was the issue!

This includes an explanation of Dwell angle and Dwell percentage: https://docs.rs-online.com/fb75/0900766b800290e1.pdf

Stephen