Dwell

[Anonymous]

Someone explained to me what exactly dwell is but I have forgotten. Can someone please explain? I'm sure I'm not the only one that will learn something

Also, what should the dwell be set at for my 64 200. It's bone stock except for the balancing. About 500 miles on a complete rebuild.

 

[Lazy JW]

Dwell is the amount of duration that the points are closed. It is normally expressed in degrees. It is partly a function of how wide the gap is set on the points, and partly a design function of the distributor cam lobes. You can control the dwell by adjusting the points, and then checking with a dwell meter. If the dwell is correct, the points are properly gapped. If you are confident in your point gapping ability, the dwell test is redundant.
As the distributor rotates, the points open and close, triggering the spark. The points must be closed long enough for the coil to build up enough energy for the next spark, a smaller gap allows a longer dwell time for this to happen. But, if the gap is too small, then the points won't open far enough to make a clean break of the primary current, so a compromise had to be reached. Most systems use somewhere between .015"-.025". That is read as fifteen to twentyfive thousandths of an inch. Always set the dwell (point gap) first, then adjust the timing as changing the gap will alter the timing. I don't have the specs for your engine here, maybe someone else can help?
Joe

 

[Anonymous]

I always thought that dwell and point gap were different but related things. I mean, why would you mess with a dwell meter if you can just use a feeler gauge and screw driver and set the gap?

 

[Lazy JW]

I always thought that dwell and point gap were different but related things. I mean, why would you mess with a dwell meter if you can just use a feeler gauge and screw driver and set the gap?

Some folks aren't as good with a feeler guage as they think they are. A dwell meter is a handy way to check the points after they have been run a while to see if they need re-gapping. The dwell meter was really developed for mechanics to save time rather than do the full points replacement. I almost never use my dwell meter on my VW.
Joe

 

[wsa111]

dwell should be 37-42 degrees at idle speed. hope this helps. later william

 

[MustangSix]

Dwell is related to point gap. The smaller the gap, the greater the dwell in degrees.

 

[Anonymous]

So, what do I do? Set the point gap with a feeler gauge or use the dwell meter?

 

[addo]

Dwell. Point gapping can't account for wear in the breaker cam profile.

 

[mustang6]

The way I remember this, dwell is supposed to be a more direct measurement of what is being set, and therefore superior to point gap. The whole idea is that the time the points are closed (a function of the dwell angle) is the time that the coil gets charged to build up the next spark. You want optimum dwell to build up the optimum spark. Setting point gap is an indirect, mechanical way of approximately setting dwell angle, so if you have a choice- set the dwell angle.

 

[pedal2themetal45]

HI YA
Its total up to you. But you'll get a more accurit setting with Dwell.
To set dwell You would ... pull the cap off and the rotor.. attach meter.. loosen points (bairly).. with motor spinning adjust the dewll to where it reads (I beleve) 2 deg's. above where you want to set it ( if you want 34 degs. the set it at 36 degs.) I beleve it well drop a couple of degs when its running.. You well have to check it to see which way it goes.. as you set it.. (I don't remember )
Tim

 

[Anonymous]

Ok, I think I'm starting to understand. I was tweaking the motor last night and the dwell was at 30. I also played with the timing a bit. Seems to run better but it didn't seem to have any effect on the operating temp.

 

[Lazy JW]

On most engines you need to set the gap with a feeler guage and then check the dwell. Some engines (GM) had provision to adjust the dwell with the engine running by using an Allen wrench through a little access door in the distributor. That was probably the pinnacle of breaker point distributor design. At any rate, IF you can use a feeler guage properly, your engine will never know if the dwell is one degree off. Just think about the difference in dwell specs between 8 cylinder, 6 cylinder, and four cylinder engines. The fewer cylinders, the more dwell time there is. Whenever I work on a vehicle that I am unfamiliar with, I always check with a dwell meter. But afterwards, I just don't bother as I have never found one yet that didn't come in within specs.
Joe

 

[Anonymous]

Old Saying:
Points to big=dwells to small
Dwells to big=points to small
I also thought the dwell was a way to check for worn dizzy shafts and point spring float. If you see a veriance in the dwell during an RPM increase your shaft bearings could be worn?

Steve