tach/dwell meter

[DJK]

What's everyone using for a tach/dwell meter? My 40 yo Mac ET910 is only giving me voltage readings, tach and dwell no longer function, have replaced the 9v battery and cleaned all connections.

Thanks

[Sniper]

I have a very old SunPro tach/dwell meter, CP7603, I use. 

[busycoupe]

I have an old Sears dwell/tach that works off of the cars battery; no 9 volt battery involved.  The instruction say that it is for 12V neg. ground, but it works fine on my 6V pos. ground '48 Dodge.

Edited May 10, 2021 by busycoupe
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[chrysler1941]

1 hour ago, DJK said:

What's everyone using for a tach/dwell meter? My 40 yo Mac ET910 is only giving me voltage readings, tach and dwell no longer function, have replaced the 9v battery and cleaned all connections.

Thanks

How are you connecting it for dwell reading?

[Booger]

1 hour ago, busycoupe said:

I have an old Sears dwell/tach that works off of the cars battery; no 9 volt battery involved.  The instruction say that it is for 12V neg. ground, but it works fine on my 6V pos. ground '48 Dodge.

I have same. Found on CL for $20. 38* yup

[Plymouthy Adams]

I decided to buy my last hand held meter VOM with these capabilities built in, dwell and tach multiple settings for/from 1 cyl and up

Edited May 10, 2021 by Plymouthy Adams

[DJK]

Found an Actron CP7677 on Amazon for $44, should get it Weds. See what happens. Thanks guys.

[Plymouthy Adams]

I have used the Actron as my friend down the street has one.  I think you will like it.   Mine is a different model with a few more features including cap test and temp probe.  I told my son about using the Actron and he got me instead this unit instead as it has more features he will want to borrow it for later.

[keithb7]

4 hours ago, DJK said:

Found an Actron CP7677 on Amazon for $44, should get it Weds. See what happens. Thanks guys.

 

I sure like the look of that unit. Please let us know how well it works with 6V. Dwell and RPM. 

[DJK]

Will do.

[Hamilton]

On 5/10/2021 at 6:47 AM, busycoupe said:

I have an old Sears dwell/tach that works off of the cars battery; no 9 volt battery involved.  The instruction say that it is for 12V neg. ground, but it works fine on my 6V pos. ground '48 Dodge.

This exactly the unit I use.  After the one I'd had for about 35 years took a dump, I found this one at a garage sale for fifty cents.  Being a cheapskate at heart I offered a quarter, which they readily accepted.

[Plymouthy Adams]

you know...you can call yourself a cheapskate...but in yard sales and such, swap meets....bartering and dickering is 99% of the fun....

[DJK]

There are a couple of the Sears units on ebay for the price of the new Actron with a lot more features. Should be here today.

[DJK]

My 80 yo buddy showed up with his vintage Snap-on tach/dwell meter, checked my settings, had 38 degrees on the dwell and 500 rpm. Waiting for my Actron to show up.

[DJK]

Actron showed up, checked dwell = 38, would not give a steady rpm reading. Called the company, they said 12v system is all it will work on for tach. I can set the rpm pretty well by ear and apparently I did a pretty good job with the points and feeler gauge. 

[Los_Control]

Not sure how it works on dwell, but a trick as a example for a timing light. Set a 12 volt battery near and connect the timing light power to 12 volt, the plug wire to your engine.

 

There is a gentleman @Tubman That makes a kit to convert a 12 volt Tach to a 6 volt + ground. This means you supply your favorite 1960's tach and connect it with his kit ... If you wanted a tach in your car. Any 12 volt tach works.

Which is kinda off topic for your question, because not a tool, but is a fully functional tach installed .... I guess you could just connect the wires and hold the tach in your hand like a tool then store it in your tool box? 

 

Just saying option is available, I bought a condenser he also makes, is Brass and mounts outside distributor, quality work. I would like the tach later. Keeping track of rpm on the old flatheads is key while driving.

 

[keithb7]

My 70's snap-on dwell/tach tool was buit for the 12V era. It hooks up to the car battery and coil. It will read dwell with 6V, but I'm having issues with the tach function. It doesn't seem to want to read RPMs. I tried hooking the tool up to a spare 12V battery. Placed on the floor near the car. The RPM still won't read. Maybe the tool is actually not working properly? Dwell is just fine though.

 

Recently I tried a modern, mini digital tach with hour meter. It has it's own CR2032 battery in it. It's a small unit. A lead wire wraps around 1 spark plug wire. It can be used for single or multiple cylinder engines. 2 stroke or 4 stroke. It seems to work. I can get RPM, max RPM is recorded. Running hours is recorded. Seems like a cheap easy option. I saw them on Amazon and ordered one to try. 

 

I plan to use it more and somehow verify that the RPM reading is accurate.  It seems real close based on my ear.  The gauge updates quickly so you get decent RPM readings. You can even program a warning zone so that at a certain RPM it warns you. The screen turns red I believe.

 

See here: https://www.amazon.com/Backlight-Maintenance-Tachometer-Motorcycle-Lawnmower/dp/B08F25C1JW/ref=sr_1_9?dchild=1&keywords=digital+tachometer+hour+meter&qid=1620862576&sr=8-9

 

 

Edited May 12, 2021 by keithb7

[DJK]

1 hour ago, Los_Control said:

Not sure how it works on dwell, but a trick as a example for a timing light. Set a 12 volt battery near and connect the timing light power to 12 volt, the plug wire to your engine.

 

There is a gentleman @Tubman That makes a kit to convert a 12 volt Tach to a 6 volt + ground. This means you supply your favorite 1960's tach and connect it with his kit ... If you wanted a tach in your car. Any 12 volt tach works.

Which is kinda off topic for your question, because not a tool, but is a fully functional tach installed .... I guess you could just connect the wires and hold the tach in your hand like a tool then store it in your tool box? 

 

Just saying option is available, I bought a condenser he also makes, is Brass and mounts outside distributor, quality work. I would like the tach later. Keeping track of rpm on the old flatheads is key while driving.

 

That is how I have to use my timing lite w/ 12v jump box. I have seen the converted tachs, may be an option. A 6v Westach is around $150.

[Los_Control]

I have some communication on the Tach somewhere, can not find it. He made a youtube video That showed and explained the workings of it. With it connected to a old flathead on a run stand.

I only know to contact them through the H.A.M.B. or the Ford Barn through a personal message. I am guessing, iirc the kit was $100 or a little more. But does not include the tach. You can get a tach from autzone or spend a few $$ on a vintage refurbished tach ... your choice.

Here is the condenser I bought from them ... I think is quality work.

 

 

[chrysler1941]

The problem with modern instruments, digital and earlier analog is undersized input filtering for the high tension spikes occurring at ignition coils with points and especially 6 volt models.

Not to bore you with details but these instruments cannot read pulses because they overwhelmed with signals. They have a hard time distinguishing  between points opening and closing pulses and the charge/discharge of HT coil's harmonic spikes.

 

Older analog Dwell/RPM meters had large filters. If you look inside one, it's mostly a huge condenser and a specified coil. This is a Low-pass filter.

 

It is possible to use modern instruments and digital tach readers designed for 5v square pulses with additional filtering.  Alternative (and easier) using a Schmitt trigger or a solid state relay circuit as filters. These are available cheap ($2-5) on eBay.

[Tubman]

I will jump in here and will tell you that we are fully aware of the "dirty power" situation that is present in all 6 volt cars with generators. There is more circuitry in our "Tachometer Drivers" to damp the voltage spikes and other power variations than there is to do the actual tachometer driving.

 

The condensers have been in the field for over 5 years and over 300 units with NO reported failures.

[DJK]

Went to the first cruise in of the season last nite, stopped at my former service managers house for a visit. He gave me a Snap-on MT500 meter, hooked it up this AM, works great.

[Kilgore47]

I have had this meter for decades.  There are no names on it so I have no idea where it was made.  It came in a set.  A timing light, a remote starter button and the meter.  Still have all three.  Haven't tried it for a long time so no idea if it still works.  Took it apart to look inside and the circuit board is hand soldered.  There are some numbers but no names.  

[Tubman]

These things are essential when setting up dual point distributors. I set the Mallory in my car by the point gap specified by Mallory, and couldn't get it to run for ****. I got a cheapo (unpowered) Tach/Dwell meter on eBay, blocked the individual point sets open and set the individual dwell It worked perfect. When I unblocked the points, total dwell was right on. Looking back, I believe that the specs from Mallory were for a different model distributor, or just plain incorrect.