Dwell Angles and 1850 Dizzys

Message

anthony rld900r · #1 Post by **anthony rld900r** » Thu Mar 04, 2004 5:19 pm

Okay, the person who designed the 1850 dizzy, it's location and how to change points deserves shooting and obviously never serviced their own car<img src=http://www.ezboard.com/intl/aenglish/im ... ns/mad.gif ALT=">:"> <img src=http://www.ezboard.com/intl/aenglish/im ... ns/mad.gif ALT=">:"> <img src=http://www.ezboard.com/intl/aenglish/im ... ns/mad.gif ALT=">:"> (especially an auto....) 
 
I currently have a dwell angle (checked with 2 meters) on my points of 42 degrees, whereas book sez 39 +- 1 
 
Question, as I've forgotten the answer, what will 42 degrees do to my ignition, timing and general oooomph? (plugs and leads are new, coil okay, but it all feels a bit tired and lacklustre on driving - maybe the cold weather?) using LRP or unleaded has no noticeable effect either and I haven't been able to check the timing yet as (a) strobe light is a bit weak and (b) can't see the marks on the pulley wheel because of (a) and general crud on marking lines (must clean the oil off!!) 
 
On closer inspection also, the vacuum advance doobrey on the dizzy is a bit bent as well - angled, not straight, looks like it had a bash at some time in it's existence. 
 
Recommendations / ideas please on how to check the dizzy for proper operation and tips on how to change / reset points when you can't even see the bl<img src=http://www.ezboard.com/intl/aenglish/im ... ns/mad.gif ALT=">:"> <img src=http://www.ezboard.com/intl/aenglish/im ... ns/mad.gif ALT=">:"> dy dizzy cam to see if the points are open or not because of the weights... (no, I don't want to fit electronic in case it all goes t<img src=http://www.ezboard.com/intl/aenglish/im ... ns/eek.gif ALT=":eek"> ts up, because of the cost and as I've got plenty of spare points) 
 
I will probably have to resort to taking the dizzy off and having read previous threads, that's a pain in the posterior an' all..... 
 
Help! It's cold outside <img src=http://www.ezboard.com/intl/aenglish/im ... /frown.gif ALT=":(">

george · #2 Post by **george** » Thu Mar 04, 2004 10:18 pm

remove one of the weights and you can just about set the points be careful you dont drop the spring with cold hands !!!!!<img src=http://www.ezboard.com/intl/aenglish/im ... s/roll.gif ALT=":rollin">

Jon Tilson · #3 Post by **Jon Tilson** » Sat Mar 06, 2004 1:01 am

after owning an 1850 this long you've just discovered the major joy of owning one.... 
Take the weights off the top and you can see the points gap fine. Be careful you dont have the points set to 15 thou open when on the closed part of the cam...my favourite non starting trick...points open all the time.Sorry Rob!. 
An auto makes stuff all difference BTW they are all a PITA. WHy couldnt they use a lucas dizzy. 
Fit an electronic ignition mate...its worth it. 
Clean your pulley and marks and set it up static at 11 BTDC or whatever the book says. Suck the pipe and see if the base plate rotates. Make sure the springs and weights are all well greased and work. New condensor is a good idea. 
Jonners

Paul · #4 Post by **Paul** » Thu Mar 18, 2004 1:04 am

the dwell angle is the angle the dizzy shaft turns while the points are closed. 
 
while the points are closed the coil is charging. 
 
when the points open the coil discharges to make a spark at the plug. 
 
the larger the dwell angle the longer the coil charges and the later it discharges, meaning the ignition timing is retarded. 
 
your engine may feel a little more responsive with the carrect dwell angle of 39 degrees, making the timing a little advanced to what it is now. 
 
Professor Paul

Paul · #5 Post by **Paul** » Thu Mar 18, 2004 1:10 am

points gap isnt a very accurate way of setting the dwell angle. 
 
the smaller the points gap the smaller the dwell angle, so, the larger the points gap the larger the dwell angle. 
 
Paul

Chris Field · #6 Post by **Chris Field** » Thu Mar 18, 2004 10:18 am

Smaller gap = larger dwell (as you said earlier, dwell is the length of time the points are closed) 
 
Chris

anthony rld900r · #7 Post by **anthony rld900r** » Thu Mar 18, 2004 11:35 am

The larger dwell angle is then probably why it runs okay on unleaded! 
 
What does 42 degrees dwell translate to in a timing angle? - I know the standard should be 11 BTDC with 39 dwell, so does anyone have an idea?<img src=http://www.ezboard.com/intl/aenglish/im ... ohwell.gif ALT=":">

Jon Tilson · #8 Post by **Jon Tilson** » Thu Mar 18, 2004 1:20 pm

of knowing cos we dont know if your dizzy is set up at 11BTDC with the correct dwell.... 
Get a timng light, set the dwell and see how it runs. I get no pinking at all on any of my fleet even on crap Supermarket stuff. They do all go a bit better on optimax though. 
Jonners

Paul · #9 Post by **Paul** » Thu Mar 18, 2004 8:36 pm

yes chris you are right, thanks for pointing it out. 
 
Paul

Malc · #10 Post by **Malc** » Thu Mar 18, 2004 11:53 pm

I don't do the job so much these days....ECU's et al, so i'm a bit rusty, but IIRC my trick for remembering it all was one of opposites. Reducing Points Gap Increases Dwell Angle and Retards Timing and vice versa.. 
 
Don't dwell on it though

The Triumph Dolomite Club - EzBoard Archive