The Stovebolt Site Forums The Shop Area Engine Shop Dwell/timing point gap questions

I used to just set the gap to .019 and forget it years ago. Now my kid says I should set it according to the dwell. I set the points to 19 and set the rpm to 475 and the dwell was about 36. I guess 28 to 35 is what the dwell is supposed to be. I had to open the points to .0025 to get the dwell to 30. What is the matter with me? Is that acceptable or is something wrong? - Thanks - Scott

I think you need to use dwell. Dwell is an electrical measurement of the time the points are actually closed. Since the coil is charging when the points are closed, correct dwell is important.
In my experience, point setting and actual dwell can vary by a significant amount. If the dist. bushings and point cam are in good condition, then point gap and dwell should match. When dist bushings wear, the slop can allow the cam to move away from the points,changing the actual gap under running conditions. Sounds like what you are describing.

The worst case I ever saw was a 58**** with a 292.
When the points were gapped to .016 the engine wouldnt start. If the points were set to around .005, the engine would run. The dwell at .016 was nonexistent (meter didn't read) but at .005 it was around 22 or so. New (rebuilt) dist. cured the problem.

My 5 cents

Curly

Ralphy/Curly
Thanks for the tips. I suppose the distributor wear is the problem. Although, Curly, you had to set the point gap low to get a higher dwell .005/22, while I had to set the gap high to get low .025/30. But, you are talking F*** and I am Chev. so it could well be reversed. Thanks again for the tips! - Scott

..What Curly said ~ the dwell is a function of coil saturation so more dwell is better (within reason) .

The easy way to set the dwell is to crank the engine with the plugs out and dizzy cap off & set it whilst the dizzy is in motion . you have the plugs out during tune up anyway , right ? .

Once it's back to-gether and running , check the dwell again and goose the engine , more than 3 degrees variation when the engine revs up and the dizzy bushings need replacement . remember , one degree change in dwell works out to 3 degrees timing drift , a bad thing in all cases .

Nate,

Sounds good! A number I can deal with and a solution that is logical and fits in with the other guys. Just replace the dizzy bushings, not the dist. cam is enough right? Thanks - Scott

yes, bushings should be enough. Eyeball the cam, it should be ok.
For what it is worth: A rule of thumb that I had memorized back when I was turning wrenches--

The smaller the point gap, the higher the dwell.

Closing the points increases dwell, opening the points lowers dwell.

When I had to make changes to points to correct dwell I would mutter that to myself to figure out which way to move the points.

Ralphy,
Thanks for your efforts. Maybe that is my problem....I'm shooting for the wrong specs. I have what I believe to be the original engine and dissy, but I will have to check the numbers you mentioned. Also, my dwell number was too high, so I had to open up the point gap to bring the dwell down, not the other way around. I was shooting for 28 to 35 dwell and .019 point gap, but that was not going to be possible with the correct dwell, so I opened up the gap to about .025. But, judging by some of your numbers, a 55.1st may need different settings the the one's I've been shooting for. It has been kinna cold here, but I think I will get out to the truck on the weekend and check those stamped numbers you mentioned. Thanks for your efforts! - Scott

Also, does anyone know where to get these distrubutor bushings? Do I need a part number or is the year good enough? Is this a NAPA thing? Thanks again - Scott

Ralphy,
I finally dragged myself out in the cold and looked at the distributor numbers:
Model 1112396
Serial4K05
Delco Remy Anderson Indiana.
Please let me know if you have the point gap and dwell.

Thanks for going to the trouble for me. - Scott

Ralphy and all,
Thanks again for your efforts! That pair of dwell/gap numbers should be within my grasp without having to favor either one. However, I will check the dwell drift number also, to see if the distributor has too much play in it. Ah...this is great! Thanks again! - Scott