Points Gap on 70/71 US Distributor

[Naj ✝︎]

What should the points gap be on a 70/71 US spec car with transistorised ignition( 062 )?

naj

[Iconic]

Naj,
The BBB page 00-0/1 states the 062 should be at 0.4 mm (rounds to 0.016 inch).
I've read that 0.3 mm (.012 inch) works well (I can't tell you where at this point).
I set mine at 0.3 mm and it works without any issues.
Mark

[Naj ✝︎]

Thanks, Mark,

I had the same problem as you. Stuck distributor. Managed to shift it with penetrating oil and force.

All in order now.

naj

[menesesjesse]

While the point gaps vary from 12-16 thousands as a place to start it is more important to make sure the dwell is right.  I always use 12 as a starting point but seem to adjust it after to achieve my dwell reading
jesse

[Benz Dr.]

The aluminium units use a different dwell angle which is 30 degrees. Point gap relates directly to dwell angle.
 If the car starts to miss at higher speeds try closing the gap a small amount. If it's missing all the time, open the gap a bit and see what happens.
 I set up using my tester but the gap usually rests around .014''

[Iconic]

While the point gaps vary from 12-16 thousands as a place to start it is more important to make sure the dwell is right. 

I believe if you are careful when you gap the points and the car drives correct, there is no need to check the dwell. Point gap and dwell are just two different ways to measure the same thing. The amount the points open when being pushed out fully by the distributor cam.

[abe280SL]

I always set the dwell @ 38-41 after initially using a gauge.
abe

[graphic66]

 I copied this info from another site, it really explains the whole dwell thing, it is basically how I have always set the dwell except I have never removed the spark plugs, next time I think I will. You can adjust the points while turning the engine over with a screwdriver, just remember to remove the rotor or it can hit your screwdriver and break. After you put the system back together and start the car you will see the dwell will have changed. Now, start over and subtract or add the difference in running dwell and your dwell while turning over with the cap removed and set your points while turning the engine over with a screwdriver to the value determined. You may need to do this a couple of times to get it perfect while idling. 
    I installed the $30.00 Vellemann electronic ignition and my car has never ran better. I think that electronic system makes setting the dwell and your points condition less important in how your engine runs.
    Here is the explanation I copied;
    At ordinary engine operating speeds, the points open and close a couple of hundred times per second, the exact number depending on the number of cylinders and the engine RPM. The points need to be closed for a appreciable time in order to build up the maximum magnetic flux in the ignition coil core.

The period of points closure is specified by the ignition system designer and is typically expressed as degrees of distributor rotation. In a four cylinder engine, the angle between each ignition cam lobe is 90° and the period of points closure or "DWELL" is usually a bit over 45° of distributor rotation. In a six cylinder engine, the lobes are 60° apart and the dwell time is 30° to 35°.

The dwell is adjusted by setting the points gap to a specified distance at maximum opening. A narrower gap gives more dwell and a wider gap gives less. Taking it to extremes, excessive dwell means that the points close too soon after opening, cutting off the magnetic field collapse before it delivers all its energy. Too little dwell gives the magnetic flux insufficient time to build up to the maximum.

Both conditions give a weak spark which gets even weaker as the engine RPM rises and produces misfiring at normal operating speeds. The dwell, as well as spark plug gap, do have an effect on ignition timing. The later the points open, the later the spark comes and retards the timing. The earlier the points open the sooner the spark comes and advances the timing. That is why timing is the last thing to be set in a tune-up.

The way I set the dwell is this; remove the distributor cap and rotor, ground the coil wire and remove all the spark plugs from the engine. Set up your dwell meter and hook up a remote starter. Turn the key ON and crank the engine. Adjust the points to the desired setting and tighten the points. Crank it again to be sure the dwell angle is still correct.

[stickandrudderman]

Setting the dwell is by far the best way to set up your points. It's a dynamic setting rather than static.
Setting the dwell takes into account any play in the ditributor shaft and so is very accurate.
Proof of this is that, as already stated, you start by setting the dwell at cranking speed but then fine tune with the engine running because it's never right first time!
When you've set points quite a few times you'd be surprised at close you can get the gap just with the naked eye!

[Benz Dr.]

This is what a distributor tester does. It spins the distributor at different speeds while you make adjustments. It's far more acurate than any other method because you can see several different functions all at the same time.
Aluminium distributors are generally 30 degrees of dwell. Setting point gap isn't close enough in most cases but it's a starting point. Dwell angle is by far more important than point gap. Many diistributors loose a lot of dwelll angle at higher engine speeds due to worn bearings. When you loose dwell angle you loose ignition timing because the points are closing up.