Points V/S Dwell

[Frank Gooz]

I could use some information please. I am working on my 1950 Dodge Coronet. I put in new points and thought I was very careful when setting them on the bench to .020.

If my dwell meter only shows a dwell reading of 21.  Is my point gap to big or to small? Shop manual said I should be 34 1/2 to 38.

 

Thank all of you , you come thought

Frank

[Frank Gooz]

I think I found out that my gap must be to big, I will check tomorrow.

[Pete]

Your point gap is too small. Dwell measures the time the points are closed.

 

Pete

 

[Doug&Deb]

I’ve had better luck setting points with the distributor out of the car. It’s tough to see that far down in the engine compartment. Manually turn your engine to tdc on number 1 cylinder before removing the distributor. This also gives you a good reason to check your timing when finished.

[busycoupe]

1 hour ago, Pete said:

Your point gap is too small. Dwell measures the time the points are closed.

 

Pete

 

I think that just the opposite is true.  If the points gap is too small then the points will be closed for more degrees of rotation and the dwell will be larger. In your case the gap is too large, accounting for the small degree of dwell. 

[rallyace]

Dwell is more important than the actual point gap as the dwell is the amount of time the points are closed and charging the coil. Point gap and dwell work in opposite directions, smaller point gap means larger dwell and larger point gap means smaller dwell.  Set your points for the proper dwell. Once you have your dwell properly set, set your timing based on vacuum, you want the maximum smooth vacuum at idle for the correct timing.

[keithb7]

I like to hook up my dwell meter. Fire up the car. Note dwell degrees. Then I tweak the points. Flash up the engine. Recheck dwell. Adjust if needed. Rinse and repeat until done. Dwell time is important to get a nice hot spark that can jump the air gaps efficiently. 

 

 I reach in there and tweak the points, leaving distributor in the engine. Its a pretty quick and easy task. If I am replacing points and or the condenser, I agree, pull the distributor. Much easier working on it on the bench. 

 

 

Edited September 6, 2021 by keithb7

[Pete]

Busy Coupe - you are correct. The point gap is too wide.

 

That's what I get for responding before I've had my coffee.

 

Pete

 

[Frank Gooz]

I want to thank everyone for a response.

Enjoy your holiday.

[Merle Coggins]

I have checked and adjusted the dwell while cranking. Remove the cap and rotor, loosen the points adjustment screw slightly, crank over engine and watch dwell meter while making fine adjustments. Lock everything down when you have it where you want it, reinstall rotor and cap, fire it up and double check the dwell.  

[LazyK]

bigger gap = less dwell

smaller gap = more dwell

[TodFitch]

10 hours ago, rallyace said:

Dwell is more important than the actual point gap as the dwell is the amount of time the points are closed and charging the coil. Point gap and dwell work in opposite directions, smaller point gap means larger dwell and larger point gap means smaller dwell.  Set your points for the proper dwell. Once you have your dwell properly set, set your timing based on vacuum, you want the maximum smooth vacuum at idle for the correct timing.

Too a point more dwell is better. The wider the points open the quicker the DC arc between the contacts is quenched and the spark actually happens. If the dwell is  too long (point opening too small) you won’t get good spark (no quick cut off of primary current) and will burn the point contacts out quicker.

 

That is the reason for distributors with two sets of points each running half the cylinders. For the same point gap you can have much longer dwell times. Also that is also one reason for electronic ignition, the other one is that you don’t have the wear on the block on the point arm wearing (or in extreme cases the cam on the distributor shaft).

[chrysler1941]

I never use feeler gauge, dwell is more precise.

 

I purchased a newer cap, drilled two holes above adjust and set screws and use  plastic screwdriver to adjust dwell while engine running. After adjustment, remove cap and tighten with normal screwdriver and double check.

 

Plastic screwdrivers are called alignment tools and used for high frequency circuit adjustments.

 

 

 

[Sniper]

How do you miss the rotor spinning around when adjusting the dwell with the engine running?

[Merle Coggins]

31 minutes ago, Sniper said:

How do you miss the rotor spinning around when adjusting the dwell with the engine running?

 

Exactly… I made the mistake of forgetting to remove the rotor one time while doing the adjustment while cranking. The rotor came around and knocked the screwdriver out of my hand, which also broke the rotor.

 Luckily I had a spare on hand.  

[48ply1stcar]