Points Gap or Dwell Angle?

[David53]

Going to treat the 803 to a bit of a tune up tomorrow. What's the consensus regarding points gap? Feeler gauge or via dwell angle? Surely the dwell angle approach is more accurate?

[IslipMinor]

Setting the points to a 'gap' is the convenient means of achieving the 'dwell angle', which is what is really required. It would be interesting to set the points conventionally and then see what the resulting dwell angle is?

I'm sure there will be other views!!

[autolycus]

I'm still trying to get my head around my new toy - a Crypton tuner from the mid-80s - having rather gone in at the deep end trying to set up a twin-contact Delco-Remy with 3-lobe cam, but I've read that I should be able to see the effect of dwell variation with speed and variation between cylinders, say as a result of a bent shaft or worn cam. It's going to take some mastering, but should be a great tool if I ever manage.

I need something like a Morris 8 to practice on, where the distributor is nicely accessible, but I'll try it on the Midget to see what dwell angle I get.

Kevin

[bmcecosse]

The gap and dwell angle will vary for each lobe of the dizzy cam. All you need is enough gap for the spark to occur - and then the points close to charge up the coil/condenser couple. So - to maximise charging time you want the smallest gap possible - the risk then is that some wear will take place and the gap will disappear - probably on one lobe first causing missfire and poor starting, slowly getting worse and worse. So it's a compromise! The normally quoted 12 thou is fine - but 5 thou would be better IF you are willing to check/regap regularly. Adjusting the points will upset the timing slightly - so be sure to optimise that after doing the points - whatever method you use !

[David53]

Thanks, will set to 60 dwell and then check the timing using the "advance until pinking" method. Is there a way to check for pinking with car stationary (ie: without having to go out and find a nice long hill?)

[bmcecosse]

No -the engine has to be under maximum load. But if the CR is low - it may never 'pink' . Have you ever heard it pinking before ? How does a 'dwell' meter measure angle??

[beero]

I don't think it measures the angle BMC, it measures how long the points are closed in relation to how long they are open. So if they are closed for twice as long as they are open, then it can be expressed as 60 degrees to 30degrees out of every 90 degrees.
Anyway, I have used one for years and even on a really worn dissy there has never been more than 3 thou error so it won't make a lot of difference. It's just a good way of double checking (in my opinion)

[bmcecosse]

I agree Beero - it's measuring the mark/space ratio. not an 'angle' at all. I have never had such a fancy piece of equipment - I just use a corner of a fag packet.......

[beero]

Fag packet will of course do just as well !! But I do like my toys.

[David53]

Yes not sure why it's called the "angle" either but it's a nice easy accurate way to do the job. Roy, no have never heard the engine "pink" - I think you're right, with compressions of around 120 it's probable it won't pink at all. Any other tips for setting the timing, bearing in mind I have no timing marks on the timing chain cover? Not keen on the "twist until it sounds right" method.....

[David53]

Well, replaced the plugs and reset the points gap (Dwell angle was 30!). Then set it to a fast idle and twisted the dizzy until it ran smoothly. Will road test as soon as the weather clears up. It must have been a bit too far advanced, as twisting slightly to the left smoothed the idle nicely. Just a question - was only able to turn it just so far to the left then it stopped and I could not turn it any further. Is is just a case of the clamp bolt not being loose enough?

[bmcecosse]

All you can do is twist for best idle then - provided it doesn't kick against the starter when starting from cold - or pink under load. If the clamp has slots - obviously it can twist a very limited amount in the slots - after that the clamp would need to be loose enough to allow the dizzy body to twist within the clamp frame.

[JOWETTJAVELIN]

Also be careful not to do what I did when setting the dizzy: snap the metal vac. pipe.

[David53]

Yes, disconnected the advance pipe prior to turning. Hopefully a road test will confirm that it's all about right

[katy]

Yes not sure why it's called the "angle"

It's a measurement of how long the points are closed, hence the word "dwell", and it's measured in degrees of distributor shaft rotation, hence the word "angle".

[lambrettalad]

so it's the angle of the dangle ?

[David53]

Well mine was on 30, so points closed for half as long as they should have been, obviously due to them wearing down a bit. Sun is out today so off for a road test!

[bmcecosse]

Is that 30 degrees (out of possible 90) OPEN - or CLOSED ?? The points should be open for minimum time to allow maximum time for the recharge.

[David53]

60 closed, 30 open. So closed twice as long as open.

[IslipMinor]

60° is spot on, the 'dwell' should be 60° +/-3° according to the manual.