Dwell Settings - Trial & Error?

[Bruce Allert]

I've been playing around with the dwell angle on my 73 1.7 with D-jet to see if one setting is better than another. Since the given spread (according to Haynes) is from 44 to 50, there must be one that is best.
So far I've tried 3 different settings (re-timed each setting).
Is this the way dwell should be set, by trial & see which is best & how it drives or is there a way to find out which dwell angle is best for your car before you set it?
bruce

[bob174]

The dwell angle is the number of degrees of crankshaft rotation that the points are closed. This translates to the period of time that the primary coil windings of the coil are building up a magnetic field that will collapse when the points are opened and induce the high voltage in the secondary windings of the coil (did I reverse this--it's been a long time) that ultimately causes the spark at the plug. Therefore, when you set the dwell angle, you are ensuring that the points stay closed long enough to generate sufficient voltage in the coil to give you a good spark. As a result, you shouldn't notice any difference in your engine's performance for any of the dwell angles that are within the factory spec, IMHO. I guess you could potentially see a performance drop off with a low dwell angle at high engine RPMs if you had a worn distributor where the points weren't remaining closed long enough to build enough of a magnetic field in the coil to induce a strong spark?? Anyone else want to weigh in or correct me??

[John Rogers]

If I remember correctly, with points as they age the dwell goes up which changes timming (as you've found) and that affects performance. I always tried to get dwell right in the middle or slighly low and then set timming a degree or so ahead and over time they come right into spec and then drop off. But that's why I use Compufire units in both distributors now and it NEVER changes so over a couple of years they pay for themselves in the time I saved working on dwell! Good luck.

[pbanders]

When I had points, I set them like John Rogers describes, in the middle of the range, so that when they'd wear, they would have some margin. Now with my Crane ignition, it's not an issue.

Be aware that at high rpm, the coil does not fully develop the magnetic field in the primary before the points are opened, resulting in lower spark voltage. CD (capacitive discharge) ignitions permit much higher engine speeds with good spark voltage.

[Bruce Allert]

Then it's decided... I will set the points and the next time I do anything with this area of the car will be to install the electronics. Thanks for the info and making this understandable.
bruce

[HMeeder]

Bruce;

I did much the same as you. Tried different settings and opted for the low end of the range with a degree or 2 of advance. Over time the dwell increased and that way I figured I had the longest period of accuracy. Since then, I have tried different electronic ignition modules. I had horrible luck with the Pertronix units (though others claim great results) and like John, I now use the Compufire unit. No more points ever! I'm happy with the way it's set up. Now if only the valve hadn't crashed through the piston...

[Bruce Allert]

One more thing... A few posts back someone mentioned the electronic ignition along with a specific coil and something else. All totalled to around $175. What was this configuration?
bruce

[dave blackburn]

Bruce, here is the post, MSD, new coil and ignitor.

Dave

[Bruce Allert]

Thanks Dave, I searched for 30 minutes for that. I'm going to save it for when it's time to buy. Have a great Turkey Day.
bruce