TheSamba.com :: View topic - Massive point gap to achieve correct dwell

Sun May 11, 2025 1:16 pm

I checked my 67 point gap. It was very tight, about .010 or less. Dwell was around 90 so I decided to widen the gap.

Note that the car runs fine, but I want to understand this before I drive it much. I know that dwell affects timing, so I want to make sure it’s right so I can properly set the timing.

Long story short, I’m at .020 and the dwell is still 68. I think I’d have to use a tape measure to check the gap if I go any wider! Doesn’t seem right to me.

My timing light is an Innova from Amazon so I have no idea what kind of quality it is. But it does have a dwell meter, and you can pick the number of cylinders, so I figured I’d give it a try.

So what do you think is likely to be the problem? Crappy tester? Points need replacing? Shaft lobes worn down too much? Something else?

Thank you!

Sun May 11, 2025 1:25 pm

aquifer wrote: ... Dwell was around 90 so ...

Impossible, unless your meter is measuring dwell angle of crank shaft. VW specs are for angle of distributor shaft. So you probably actually had 45°.

Sun May 11, 2025 3:15 pm

MrGoodtunes wrote: aquifer wrote: ... Dwell was around 90 so ...

Impossible, unless your meter is measuring dwell angle of crank shaft. VW specs are for angle of distributor shaft. So you probably actually had 45°.

You’re on to something here. More googling leads me to believe that the innova meter measures dwell according to crankshaft rotation. It does measure engine rpm, so I bet it just goes by that.

So that brings up two questions:

1. To convert my reading, I assume I would divide by 2 as your answer implies, because it would take 2 revolutions to complete 4 strokes. Is that right?
2. Is there a dwell meter that can measure dwell according to the distributor shaft? Or does everyone except me just know you’re supposed to divide it by two?

Very helpful, thank you! I’ll do more research but I think google is telling me that you’re right.

Sun May 11, 2025 3:25 pm

Is the timing light set to 4 cylinder?

Sun May 11, 2025 3:57 pm

Glenn wrote: Is the timing light set to 4 cylinder?
Yessir.

Sun May 11, 2025 6:58 pm

My innova reads dwell angle correctly. No issues.

Sun May 11, 2025 8:01 pm

bnam wrote: My innova reads dwell angle correctly. No issues.
I’m thinking there’s something else going on here. The more I check it, the dwell reading seems to jump around a lot, by a big margin. Google thinks that a worn bushing where the points pivot can cause this. I can move the outer arm of the points with a needle nose plier, which seems to confirm this. I think the arm is moving laterally too, not just opening and closing, which would explain why the reading is jumping around.

I’m going to replace the points and try the readings again. The Innova is probably just fine - I just have a different problem than I thought.

I really appreciate all the replies. It gets my mind headed in the right direction!

Mon May 12, 2025 8:29 am

This is why I love my 1970 Craftsman tach/dwell meter, been doing its job 55 years now faithfully. Good luck with your problem, might try borrowing a known good unit from a friend.

Mon May 12, 2025 9:26 am

Set the point gap to 0.016 inch, adjust the timing to marks on the pulley with a light bulb or volt meter to check point that points open

That should give you reasonable dwell. Dont alter point gap as you hove to make the dwell meter right.

Thus assumes too that your distributor is good condition, and correctly installed

Mon May 12, 2025 2:36 pm

Give this page a read. It is meant to check/set dwell just using crank rotation.

With just a 12v test lamp wired between your ignition coil (-) terminal and ground... measure the crank pulley CW rotation (in degrees) from the point when the points close (test lamp OFF) and where the points open (test lamp ON). This is shown above as 100deg. You should be able to guess your dwell (distributor rotation) angle by dividing the crank rotation angle in half.

Also, are your points badly pitted? Look at the two contacts of the points. New points will have completely flat surfaces that make even contact. Over time the contacts get pitted. They piut even faster when the condenser is bad of there is too little resistance in the coil primary winding circuirt.
They need to be filed flat or the points should be replaced. The contacts should be made from tungsten so you will need a dedicated point file or maybe a small diamond grit file. Point contacts will quickly wear out a common steel file.

FYI, you can set dwell before you start the engine.
Remove and ground the HT center distributor cap wire so the spark from the coil runs to ground.
Remove the cap, rotor and point cover from the distributor.
Connect the dwell meter as your instructions indicate. Set it to 4-cyl.
Lightly loosen the screw that holds down the points. It needs to be snug enough that the points won't move on their own; but loose enough so you can adjust them with a screwdriver.
Insert a flat bladed screwdriver in between the two notches in the point plate. These notches allow you to use the screwdriver to adjust the point gap.
Have someone crank the engine. They aren't trying to start it so no need to work the throttle plate. You want to limit your cranking to 10sec at one time with time between attempts to allow the starter motor to cool.
WHILE they are cranking the engine, take your dwell reading. Adjust the point gap open/closed as needed to adjust the dwell to 47deg +/- 3deg. If you can, adjust it a little on the smaller side of 47deg. As the point rubbing block wears the dwell will increase so starting a bit low is good.
Once you have your dwell set, snug down the points screw and test one last time to make sure the point gap has not changed.
Once your points are set, statically set timing to 7deg BTDC. This is good enough to get the engine running.
Reconnect the HT wire to the center cap post.
Start the engine. Let it warm up.
Once warm, set your idle timing using a strobe timing light as this is more accurate than the static setting.

Mon May 12, 2025 2:52 pm

Just a thought which may or not apply to your situation... I have an Innova unit also but use it with a 6V vehicle, so it has to be powered from a separate 12V source. I had similar problems reading dwell as you describe, with values bouncing all over the place and implausible results (all other functions were fine). I found that by adding an additional ground wire from the 12V power source neg terminal back to the body of the car solved all these problems. I don't know why, but it did fix the issue and now dwell readout is steady and behaving itself.

Wed May 14, 2025 4:51 pm

Dangermouse wrote: Just a thought which may or not apply to your situation... I have an Innova unit also but use it with a 6V vehicle, so it has to be powered from a separate 12V source. I had similar problems reading dwell as you describe, with values bouncing all over the place and implausible results (all other functions were fine). I found that by adding an additional ground wire from the 12V power source neg terminal back to the body of the car solved all these problems. I don't know why, but it did fix the issue and now dwell readout is steady and behaving itself.
You nailed it, thank you! I was using an external battery based on something I had read about how to use the Innova. Tonight I hooked it up to the + side of the coil and clamped the negative on a bumper bracket. The reading is rock solid at 44 degrees. Doesn’t fluctuate at all. I now feel better about what I’m doing. I will probably narrow the gap just a little bit to try to hit 47-50, but I’m I’m going to drive it a few times and check again. I’m way more comfortable with it now.

I’m glad you shared your similar experience with the Innova - I might not have figured it out!

Wed May 14, 2025 11:00 pm

aquifer wrote: The reading is rock solid at 44 degrees. Doesn’t fluctuate at all. I now feel better about what I’m doing. I will probably narrow the gap just a little bit to try to hit 47-50...
IMHO, leave the dwell at 44deg. As the points rubbing block wears down over time (don't forget to apply grease here) the dwell reading will increase. Setting it closer to 50deg just means you will be adjusting it sooner to bring it back into range.

Thu May 15, 2025 7:01 am

ashman40 wrote: aquifer wrote: The reading is rock solid at 44 degrees. Doesn’t fluctuate at all. I now feel better about what I’m doing. I will probably narrow the gap just a little bit to try to hit 47-50...
IMHO, leave the dwell at 44deg.

THIS. Don't overthink this !