Dwell angle-proper reading?

[mtnjag]

Always set my points but have never checked the Dwell. I see Dwell angle quote here and on Jag lovers varying between 32-35 degrees. On a search on line I see a 6 cylinder eng with points set .014-.016 (Jag Spec) should have a Dwell of 30-35.

My Dwell is rock steady at 26 degrees.

From what I read it looks like my point gap is too wide right?

"The dwell is adjusted by setting the points gap to a specified distance at maximum opening. A narrower gap gives more dwell and a wider gap gives less."

Thanks for a clarificaton.

[abowie]

Dwell angle and point gap are measuring the same thing.

The dwell angle is the number of degrees in the rotation of the dizzy that the points are closed. So as you say the wider the gap the smaller the angle.

As the dwell angle is a functional rather than metric measurement of the point gap it's likely the more accurate.

So it might be that your points are a little wide. So you could try setting them at 14 thou and see if you get a difference.

As points tend to close up over time you could just leave them alone. 4 degrees isn't much, and I'm not entirely sure that it's a linear relationship between gap and dwell anyway.

[mtnjag]

You have a point, they will tighten up with wear. And the car runs well.

Since Ive never checked dwell before I think I’ll play with the points while dist is installed in the car in the none running method they discuss in my 70s Sears “analyzer”. Guess it’s 70s. Forget when I got it. An electrical device Made in USA! Only ever used it for a tach.
See what difference it makes when dialed in. From what i read it will also effect timing .

[christopher storey]

You need to take into account that the static points gap is not usually exactly the same as the running points gap. All distributor shafts have a degree ( no pun intended ) of eccentricity in their running, so that the running gap is always larger than the static gap, and the eccentricity worsens with wear . As Andrew suggests, try reducing the gap a couple of thou

If you are a real anorak, you can try measuring the likely running gap by pulling on the shaft outwards towards the opening point and seeing how much difference it makes

[mtnjag]

So maybe i set the gap at the top end and in running it its a little out of spec. Makes me feel better about my abilities! (There’d be one of those smiley faces here but i can’t add emojis)

I’m going to see if i can do this in situ while cranking with plugs out and meter connected. I’d like to see what effect it has on timing without moving the dist. If not I’ll just pull it and close the gap a tad.

Wish it was like an old chevy with a little door In the cap to adjust points to proper dwell while eng is running.

Thanks

[mtnjag]

First the good. Adjusted the gap/dwell in place and it worked out nicely. Have it set at 34 degrees when cranking with plugs out. Remote starter switch, a little back and forth and dialed in. Running dwell same and steady with vacuum disconnected. Checking the Running dwell would seem to be at least a good check once adjusting points in or out of car.

Now the stupid. As i have said, i have not used the meter to set dwell before. Its an old school device with a bunch of analog scales for different tests with a central pivoting needle indicator. Turns out, i was looking at the WRONG scale. 26 degrees on the 8 cylinder scale is 35degrees on the 6 cylinder scale! I was in spec to begin with with a nice snug gap. I discovered it when, having trouble getting a good reading, I looked closely at the little red numbers at the end of the scale. 8 cylinder is the top and largest scale with DWELL next to it at the beginning of the scale. 6 cyl scale is bottom smallest scale. Once i discovered that everything fell into place.

Jeeeeeze.

[Bfastr]

I was thinking 26 was a bit too low. I set my gap the same way you just did and go for the 34-ish range. even after a couple years it remains below 40. my car starts right up, runs great. I know a lot of people go with electronic replacements and tell you ( us) we will never have to do this again. But I rather enjoy fiddling with points. I carry a spare points/condenser plate in my tool kit. never have had to do a roadside swap yet.
Bob

[mtnjag]

Yep, seems like i have it stable in spec. I understand whats going on their now which is nice when doing repairs! Now I’ll set points and check dwell when in to make sure I'm dialed in.

Thanks all.

[madjack4]

If you rev engine while reading dwell if it changes quite a bit dist is worn it should stay virtually the same

Regards Rob

[mtnjag]

Yes, nice little diagnostic tool . This ones nice and steady up the rpm range.