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Dwell angle vs Point Gap

O

OMC TN

New member
Hello,
I have an 89 OMC 2.3L and just replaced points and condenser. I set the point gap to .019 for beginning run per manual. I then connected the dwell meter and set the dwell to 36 per the OMC manual. In order to obtain the dwell of 36 I had to move the point gap to .031. This seems wide from the starting gap of .019. It feels like I have reduced power on the lake trying to make plane out but maybe its my imagination. Does this point gap sound correct? Thank you for your imput.:confused:
 
A 4 cylinder engine's distributor offers 360 degrees of rotation in order to fire all four cylinders.
360* divided by 4 = 90*

So..... 90* is the angle of rotation at which one cylinder's portion of the ignition system will charge (saturate the ignition coil) and discharge the coil's high tension spark to that spark plug.

Of that 90*, a certain duration is given to saturation and a certain duration is given to points OPEN.
This saturation angle/time is the Dwell Angle.

Point gap is an estimate ONLY of correct dwell angle.

Always adjust for dwell angle, and your system will work to it's full potential.



 
Are you sure that you had the dwell meter on the right setting (4 cyl vs V6 or V8’s)?
having to open up a .019 gap to that in order to get the right dwell setting seems wrong.
 
Ditto Chris re; lubrication on the cam and points wear block.

The dwell meter may not have specific settings for 4, 6 and 8 cylinders. It may simply have a scale for each 4, 6 and 8 cylinder engine.
Some do not have a scale for a 4 cylinder engine, and require that we double the value while using the 8 cylinder scale.

As Louc alludes to, make sure that you are reading the instrument correctly.
 
Yes the dwell meter does not have 4 cyl scale. It has 8 and the manual stated to double the reading for the 8. Following the guide I feel it is set up correctly but the gap of .031 seems excessive. Just does not seem to have the power out of the hole that it had. I may go back to .019 gap and compare. I thank everyone for the input. Yes I do have the cam lobes greased.
 
OMC TN said:
Yes the dwell meter does not have 4 cyl scale. It has 8 and the manual stated to double the reading for the 8. Following the guide I feel it is set up correctly but the gap of .031 seems excessive. Just does not seem to have the power out of the hole that it had. I may go back to .019 gap and compare. I thank everyone for the input. Yes I do have the cam lobes greased.
Click to expand...

As said, point gap is an estimate ONLY of correct dwell angle.

It may be possible that your dwell meter is inaccurate. Perhaps try using another one.
 
Agreed that .031 gap will limit the time that the coil saturates and will limit spark. BTW, in my OMC manual the points gap for all the engines is pretty similar, .018 for the 2.3 4 cyl, .019 for the 3.0, .019 for the 4.3 V6, .017 for the 5.0, 5.7 and 7.5. Your dwell angle should be between 31* and 34*. Something is wrong with the meter or the settings. I usually set it with the feeler gauge first then hook up the dwell meter and with the cap off and coil wire grounded I crank it over to read dwell and fine tune it. I set it to the smaller end of dwell that correlates to a slightly larger gap meaning it will stay in spec longer.
 
Back in the old days we used go-no go feeler gauges to do mechanical valve lifters and points, I had a ‘65 VW Beetle and never used a dwell meter!
that came later for our US cars like the ‘72 Chevy 5.7 with the window Delco Remy distributor
 
Theoretically, if the point gap is correct, the dwell should also be correct or nearly so.
Adjustment with a dwell meter produces more exact, consistent results ...
Source: AutoZone dot com


The dwell angle is the time or degrees in which the points are closed. The less gap, the more dwell. When the dwell is right on spec, the point gap should be also according to the OEM. Generally if you have a dwell meter, you don’t recheck the point gap once you have the dwell right. You do need to reset the timing after changing the dwell angle.
Source: community car talk dot com

Points that have been in use for some time develop a peak on one face that corresponds with a crater on the other, caused by spark erosion as the points open. When this happens, a feeler gauge no longer gives an accurate measurement of the gap.
A dwell meter measures the angle of rotation of the cam through which the points are opened and closed, and registers the dwell angle - the period when they are closed.
It can therefore be used to check the gap on worn points with more accuracy than a feeler gauge, and can be used without removing the distributor cap and with the engine running. The meter can also, of course, be used when fitting new points.
Source: how it works dot com

This topic can be argued or debated until the cows come home.
As said earlier, setting the point gap is an estimate ONLY of correct dwell angle. When all components are new, a correlation between dwell angle and gap can be established, hence the point gap suggestion that we may see in a service manual. That is good when all components are new!

However, why would we NOT want the dwell angle to be correct, over that of a point gap estimate only?

And by the way, ignition systems using electronic triggering also incorporate a dwell angle.
We don't see it, we don't adjust it..... but it is incorporated into the design.
Dwell Angle represents the angle (or time in degrees) at which the system undergoes coil saturation.
The remaining angle is the duration in which the system discharges the high energy voltage to the cylinder's spark plug, and allows a very short duration of coil cooling.

Do as you wish..... it's your engine!



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Last edited:
Actron meter.jpgthe point was, the OP was not getting a sensible read out of dwell with what he had available to him, so should he set it at a gap everyone knows is wrong, or do the best he can with the tools he has and set it at the factory spec? I say do the latter and then try to get a meter that will measure this more accurately if he's keeping the boat.....something similar to this that has a 4 cyl setting for dwell!
 
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