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Sat Dec 27, 2014 2:16 pm

First time using a dwell/tach meter (Sears analog) to measure dwell on my '65 bug. Running a 009 distributor with PICT 28-1 carb.

I checked points gap first and it is .016. But I get a dwell angle reading of 28 degrees. My meter has a 4, 6, and 8 cylinder scale and I was very careful to make certain that I was reading the 4 cylinder scale. My understanding is the dwell angle should be around 50 degrees.

Car runs fine.

Any ideas? Should I adjust (close) the points until I get the correct dwell reading?

Thanks.

Sat Dec 27, 2014 2:23 pm

.016" is a good get it running measurement. We have had to go as small as .008" to get correct dwell and can tell the difference in how the engine runs.

Sat Dec 27, 2014 2:33 pm

Be 100% sure you are reading the right scale... as the 8 cylinder scale is half the 4 cylinder scale.
Most dwell meters share the 4/8 cylinder scale and 8 is generally on top.
6 cyl scale is separate.

So if you are actually reading 28 - 8 cyl, it very well could be 56 - 4cyl which will run ok.
If it were really 28 dwell.... it would run very poorly.

Worn distributors... set it with dwell yields best results.

Sat Dec 27, 2014 2:56 pm

If the points are used you will never get an accurate measurement with feeler gauges because of the pit and bump the electrical arch creates on the points contact surfaces. If you have a dwell meter just use the meter and leave the feeler gauges in the tool box. The dwell meter is far more accurate than feeler gauges will ever be.

Sat Dec 27, 2014 4:42 pm

I have the same engine analyzer, and on the two 12-volt VW's I have owned, I have never been able to get a dwell reading that corresponds to the specified gap. I made sure I was using the correct scale, etc. etc. I finally gave up because it was driving me crazy. Now I have a 6-volt Beetle, and I use a feeler gauge, because that's what the Bentley says to do. I do it twice a year, and every few years I put in new points.

I'm no expert mechanic, so I'm not saying the others are wrong. I'm just sharing my experience.

Sat Dec 27, 2014 4:52 pm

I have virtually the same engine analyzer shown in the picture above. I'm reading from the scale that goes up to 90. Reading is 28 and car runs very nicely. Points have only 1,500 miles on them.

My car is 6v and I hooked the red lead to the positive side of the coil and grounded the black lead. The instructions say this analyzer is for a 12 volt system. Could that cause an issue?

Thanks.

Sat Dec 27, 2014 4:52 pm

rcroane wrote: My understanding is the dwell angle should be around 50 degrees.
The spec is 47*, + or - 3*

Set using the dwell meter and ignore the gap.

Sat Dec 27, 2014 6:05 pm

rcroane wrote: I have virtually the same engine analyzer shown in the picture above. I'm reading from the scale that goes up to 90. Reading is 28 and car runs very nicely. Points have only 1,500 miles on them.

My car is 6v and I hooked the red lead to the positive side of the coil and grounded the black lead. The instructions say this analyzer is for a 12 volt system. Could that cause an issue?

Thanks. 6 volt,there is your problem,the analyzer will only work on 12 volt systems,just use feeler gauges on 6 volt systems and set your points 1-2 thou more than the book,this puts your dwell at the min spec ,it will then stay in spec for longer if you do a few miles .A dwell meter is nothing more than a voltmeter with a different scale , so if you hook up a 12 V voltmeter to 6 volts then the reading will be low ,because your car actually runs about 7V you cant just double the readings

Sat Dec 27, 2014 6:46 pm

^^^^^Interesting thanks. I also understand that I can connect the analyzer to an external 12v source.

I'm going to give that a try.

Sun Dec 28, 2014 7:54 am

rcroane wrote: ^^^^^Interesting thanks. I also understand that I can connect the analyzer to an external 12v source.

I'm going to give that a try.

I have that exact meter shown. I used it to check RPM on my 6volt bug and powered it with a separate 12v battery charger and it worked fine. It's got the induction clamp for the spark plug wire. Not sure how it would work for dwell though.

Sun Dec 28, 2014 8:03 am

bugmandave wrote: rcroane wrote: ^^^^^Interesting thanks. I also understand that I can connect the analyzer to an external 12v source.

I'm going to give that a try.

I have that exact meter shown. I used it to check RPM on my 6volt bug and powered it with a separate 12v battery charger and it worked fine. It's got the induction clamp for the spark plug wire. Not sure how it would work for dwell though.

Source voltage is the problem here..
Most "modern" tach/volt/dwell meters wont operate correctly with 6 volts.
Using a surrogate battery is the best option. Using a battery charger can skew the dwell measurement as most chargers pulse voltage.

Sun Dec 28, 2014 9:19 am

VOLKSWAGNUT wrote: bugmandave wrote: rcroane wrote: ^^^^^Interesting thanks. I also understand that I can connect the analyzer to an external 12v source.

I'm going to give that a try.

I have that exact meter shown. I used it to check RPM on my 6volt bug and powered it with a separate 12v battery charger and it worked fine. It's got the induction clamp for the spark plug wire. Not sure how it would work for dwell though.

Source voltage is the problem here..
Most "modern" tach/volt/dwell meters wont operate correctly with 6 volts.
Using a surrogate battery is the best option. Using a battery charger can skew the dwell measurement as most chargers pulse voltage.

I have a similar older "12-volt" meter from Sears.

It will sometimes work if you put the power lead directly on the regulator so that is gets more than 6-7v of power. But not always.

Sun Dec 28, 2014 10:35 am

EverettB wrote: I have a similar older "12-volt" meter from Sears.

It will sometimes work if you put the power lead directly on the regulator so that is gets more than 6-7v of power. But not always.

I have done this, too, though you should not rev it much above idle since it can fry the meter if you get maximum unregulated voltage (up to 30V?) into the meter

Sun Dec 28, 2014 12:18 pm

On my 12 v system, I needed 0.018 to get 47 degrees with brand new points (IIRC). Dont forget to reset the timing after you change the point gap / dwell

Sun Dec 28, 2014 6:19 pm

One more quick question....

Would using one of those portable jump starters work for a surrogate battery, or do they pulse the voltage like a battery charger?

Thanks for everyone's input.

Sun Dec 28, 2014 7:29 pm

rcroane wrote: One more quick question....

Would using one of those portable jump starters work for a surrogate battery, or do they pulse the voltage like a battery charger?

Thanks for everyone's input.

As long as it is not plugged into 120 AC, so it is on battery power, it will work fine.