de_cat55

I am trying to set the points to the correct dwell. Any idea for a 383 strocker what the dwell should be?

Thanks,

HMR.

Larry B.

29-31 deg.. That's standard for a V-8

Ryan77

I love to learn, so please tell me what it is that you guys are talking about, I've never heard this term used towards engines before :confused:

Larry B.

Dwell is the time (in dedgees) that the points are open, allowing the condenser to charge up so when the points close, the charge will go to the coil which amplifies the voltage and fires the across the spark plug gap. It's a very simple system.

SanDiegoPaul

This is an old distributor from before the mid seventies when they went to electronic ignition. The length of time the points are closed determines the buildup of coil spark. The points are set with a 1/4 inch allen wrench thru the hole in the cap.

BTW for your knowlege, it is possible to get the dwell on a G.M. points style dist without a dwell meter. Turn the allen wrench clockwise slowly with the engine idling. Stop at the point where the engine misfires, or dies whichever comes first. Then back the points up exactly 1/2 turn and you will have achieved 30 degrees dwell. :yesnod:

WydGlydJim

Set it at just under 30, that way if the points slip (they always slip away from the distributor cam) it might still be good at 31-32.
:cheers:

Now I'm not so sure I got this right?
:confused:
disregard!
:D
Oh yes I got it right, conflicting posts here got me confused!

[Modified by WydGlydJim, 9:43 PM 7/8/2003] :crazy: :crazy:


[Modified by WydGlydJim, 9:45 PM 7/8/2003]

SanDiegoPaul

what happens is that the point's rubbing block wears down. This affects dwell...not to mention the high RPM limitations of point bounce. These are the reasons they went to electronic ignition@!

But to reduce the dwell a couple of digits because the points are NEW is counter productive. You want the coil buildup to be MAX and so why would you want to run short?

The truth is, that the dwell is SOOOO easily set that there's no reason to do what you suggested, with all due respect.

On Fords and Dodges, setting the Dwell was a MAJPITA. The General however made it easy for us from 1955 to 1975.

:party:

lars

Wow... a few misconceptions here on how the points system works. If I can be so bold, let me cover the basics:

First, dwell is defined as the number of degrees of crankshaft travel that the points remain closed (not open). Many people will refer to "point gap," which is an easy way to get the dwell in the ballpark. The point gap directly affects the dwell: the larger the "gap" the shorter the dwell and vice-versa.

The points, when closed, provide a path directly to ground for the current flowing through the "primary" side of the coil: Current from the ignition switch enters the coil at the "+" terminal, and flows through the PRIMARY coil windings, to the points, and directly to ground when the points are closed. When current flows through a coil (if you remember your high school physics class), a magnetic field is created around the coil. When the points OPEN, the current flow is stopped. When the current flow stops, the magnetic field collapses. When this field collapses, it collapses through the SECONDARY coil windings. When a magnetic field collapses or moves through a set of windings, it produces voltage in those windings (that's how a generator works). So when the primary field collapses, it produces a sharp voltage spike in the secondary coil windings, thus producing the spark.

The condenser in the distributor has nothing to do with producing the spark. The condenser just suppresses the tendency for the primary current to "arc" across the points and burn the contacts.

Changing the dwell changes the "saturation time" of the coil. The better "coil saturation" you can get, the higher the voltage will be on the secondary side. Best coil saturation is achieved at about 30-31 degrees of dwell. I like to err a little on the high side (30.5 - 30.8) to assure good coil saturation. This assures a good performance setting. 30 degrees of dwell corresponds to a point gap of about .016". "Dual Point" distributors work well because the dual points allow better coil saturation. Likewise, some of the aftermarket electronic trigger systems improve coil saturation times for better secondary voltage.

It should also be noted that every one degree change in dwell changes the timing by the same amount. As dwell increases (point gap decreases), timing retards. Since the timing, then, advances when you DECREASE dwell, you will notice that the engine will seem to idle better and faster as the dwell is decreased (due to the timing advancing). This is deceiving to some people, and results in many people setting up their engines with not enough dwell with resultant inadequate coil saturation. This will cause high-rpm ignition breakup and poor performance. So always set up the dwell (point gap) first, and then set the timing correctly for peak performance. Dwell needs to be 30-31. Total timing needs to be 36. Shorting yourself on either dwell or timing is shorting yourself of peak performance.

joe73vette

:iagree:
30 degrees for v-8's is what I remember. 39 for 6's and 45 for 4's. Joe

Ryan77

Now I understand :cheers:

Larry B.

OOPS! Thanks for the correction on the points open/closed issue. I guess I just didn't remember corretlly... I knew it hab to be one or the other. :jester I hate to give bad info...

WydGlydJim

I was referring to the whole point set slipping on the breaker plate, under the hold down screws. Not really anything to do with the allen adjustment screw. Just under 30 gives you a little room to scoot, without causing a problem. realistically, you will see absolutely no difference between 29-32. As a 5 year tune-up technician, I probably changed enough to know.
:cheers:
I do know it's fun to charge up the condenser by holding the insulated wire, and turning over the engine a few times, and sparking a wire onto the condenser body, and then carefully putting it back in the box to zap the unsuspecting next fellow!!!
:D


[Modified by WydGlydJim, 8:22 PM 7/9/2003]