On my 1950 cad the manual calls for a .013-.018 gap when new so I set it at .016. The dwell is supposed to be 31 + or - it says. Mine was reading 26. So i set the gap to .013 and got a dwell of 27. These are new points. The car seemed to run well so I took it for a drive. After about 20 minutes or so, when rolling up to a stop sign it idled low and died. Thankfully I was able to get it started but after that the idle was really low and I had to hold it higher with the gas pedal at red lights so it wouldnt die. Should I shrink the gap even more to get the right dwell of 31? That would take my gap out of the new range called for in the shop manual. The lowest they say to go on used points is .010. Its possible I got a little rust in the carb - I do have a fuel filter but a tiny bit is visible in the gl*** bowl.
Make sure your ground connection is good. I had problems like yours with two meters. I then changed the grounding connection. Both meters were then right on.
Something wrong here. I used to set GM points @ .019 (factory spec) and the dwell was within a degree or 2. Try setting them @.018 and see how she runs. You could also check the setting of the dwell meter, they had settings for 6 or 8 cyl, it makes a difference.
Incidentally I have tuned up cars where the points gap had shrunk to .003 due to wear. The car still started and ran. Not very well, but it ran. So, I suspect your stalling problem is not because of the points gap. I like to set them on the wide side of spec, because of the wear issue.
always set V8s to 28 mself - - back when I was workin a matchbook cover made a great gap setter -- [ anyone remember book matches? ] make shure ya use a littl dilectric grease on the dist lobes -- jist a touch - keeps the rubbin block on the points from wearin down Dwell, timing, carb set -- in that order -- could balance a nickle on edge on the fender after my tunes
This ^^^ It might not be the only thing causing your running issue, but with enough distributor shaft and bushing wear you can end up with really erratic point gap and dwell readings. Also, when checking dwell, make sure the vacuum advance is disconnected and plugged, especially if it's getting full manifold vacuum. Advancing the breaker plate can move the points in such a way that it will effect dwell.
The stalling could be timing. Point gap has an effect on timing, as well as timing has an effect on dwell. With your points gapped properly you can spin the dizzy with the dwell meter hooked up and watch the dwell reading change.
Point gar [dwell] affects timing , timing does not affect dwell !![unless there's something wrong w/ the distributor] dave
The point gap is to get the dwell close enough to run. After you set the dwell, forget the gap. Like it says above, dwell first, then time, then carb. Some of the new points we get now have a rubbing block that is too soft. A bit of grease, and carry the tools to adjust on the road. This is one reason Pertronix was so popular. Now their quality has gone so poor I have gone back to points.
Mechanical advance should have no effect on dwell as the advance mechanism rotates on the same centerline as the distributor shaft and does not change the relative distance between the points and that centerline. But the vacuum advance works by rotating the breaker plate. And usually the pivot point of this rotation is off to one side of this centerline. The plate moves thru a slightly different arc, moving the points with it, which slightly changes the point gap and dwell. Even on a new distributor.
As your point gap goes up your dwell should go down. Sounds like you have worn bushings in your distributor. Rotate the distributor until the points are open and then push back and forth on the shaft. If there is noticeable difference in point gap you need to address the wear in the distributor. Another way to tell, when you rev the engine above idle if the dwell drops more than 3 or 4 degrees you got a distributor problem.
I always use pertronix electronic ignition in my cars, keeps the distributor looking stock without the having to mess with points.. www.pertronix.com
New points! It could be as simple as the points cam follower is out of position in relation to the points fulcrum. Got a different set, lots of cheap Chinese junk out there. (does anyone build points in the US any more)
Sort this out thoroughly...lots of things need to be right for points to run happily over long periods of use. I too suspect garbage points, but obviously you have to have good bushings and cam before you look that way. Turn things till points are open, jerk shaft around and use feeler gauge to see if gap shifts. If shaft seems tight, keep turning and see if gap is the same on different cylinders. See if sloppy as you rotate cam against advance springs, the check vac...many of these are made with eccentric pivots, and of course wear adds in more possibilities. Run engine with vac disconnected and dwell gauge on, use Mityvac to move advance (or just **** hard on the hose if tool poor) and see if there's much change in dwell. If all is reasonably tight, recheck dwell with old points, go buy best grade from Echlin. They now have 2 grades, Lord help us. Lots to look at, but stuff has to be right for happy points.
Echlin still buys points made right down there in Independence, Kansas. You can still buy Blue Streak platinums made on shore as well. at least that's what I have been told.
The points are echlin. I didnt disconnect the vacuum advance when checking, and my meter is technically for a 12 volt but seems fine. Its a new unit from sears. The dwell drops down 1 degree when the engine is revved up. Whats strange to me is that it ran great those first 20 minutes, then the idle went low and died and from then on out didnt want to hold idle smoothly.
Ol Don nailed it. you set the "gap" as a ball park figure so that you can fire the engine up and then check the dwell. Once you get the dwell reading on the money the measured point gap doesn't mean anything. The dwell reading being more accurate of what you want than the feeler gauge reading. In simple terms once you use the dwell meter to set the dwell you DO NOT go back with a feeler gauge. Dwell changing might mean that the distributor bushings are a bit loose or could possibly be a characteristic of that particular distributor and hence the 28/32 ball park figure. One of my mechanic mentors from the past suggested that you ran on the lower side of the dwell reading for performance and the higher side for smoother running. The guys are right on the money when they said that once you change the dwell you have to go back and check the timing as even a small dwell or point gap change can change the timing. If it was running near perfect when ythe ou left the house and went on your little cruise I'd think that the stalling issue is in the fuel system. Dirt or crud in the gas tank, line or carb that got loosened up by the new fresh gas, wrong gas cap that isn't venting the tank if you only went a couple of miles before it stalled, clogged fuel filter from picking up said dirt or crud that got loose in the tank. The next time you drive it, if it stalls get out and loosen the gas cap and see if it ****s air in the tank an you hear the sides of the tank pop back out. On my 51 Merc I went though three brand new Stant vented gas caps before I got one that was actually vented and would vent the tank. That included one mile and a half walk to the gas station thinking I was out of gas the first time it happened.
If the dwell only varies 1 degree you are in the ballpark. I would set the gap at .018 but it is not critical. Then set the timing. I don't know what your problem is but it isn't the point gap or dwell. The car will run just as well if they are off a bit. Notice that the factory spec gives you 5 thousandths leeway. There must be something else wrong.
The dwell and point gap should be near the same. I would look at the contact patch on the points. They may not be hitting flat against each other. Rick
Did the dwell change between the time you left and the time you returned? If so, maybe the rubbing block wore off, or the points were not seated flat against each other and the close edge burned off, or maybe the set screw wasn't tight and the points slipped on the adjustment. If the dwell didn't change, the points are not the issue. Where do you live? Its possible that the first 20 minutes of your ride were while the choke was partially on and the carb may have been on the first step of the fast idle cam. Once you went 20 minutes, it reached operating temp and the choke came fully off, dropped the fast idle cam, and the stalling/near stalling began. A dwell setting is the average of the point openings. Each lobe of the dist cam can be off a a little in both height and exact position. When you set the gap with feeler gauges, your using just one lobe, and it may or may not be the good one, and you may or may not be at its highest position on the rubbing block. Add a little bushing wear, and you see why they want to use the average and give you a + or - number. We used to set the dwell on the bottom side of the spec on the thought that as the rubbing block wore, the dwell would remain withing spec longer. Gene
If I was there I would ***ume NOTHING and check everything from scratch. Do a compression test, adjust valves (not necessary on this car, as it has hydraulics). Tune up the ignition Starting with point gap, then timing, plug wires, spark plugs, when I knew the ignition was working correctly only then would I go to work on the carburetor. The only way to KNOW if something is working right, is to check everything step by step. I wish I could be one of the hit or miss guys who monkeys with some random thing and the car purrs, but I was never that lucky. I always had to do the job right or it wouldn't work.
Took the carb apart - loaded with rust. My fuel filter was worthless. I also snapped a carb stud. One problem after the next.
Distributor cam lobes do wear . Wear at he the tip would reduce the gap but not necessarily the amount of time the points are open.
The Jalopy Journal
