Use of old Tach/Dwell meter

[Stuart F.]

This may seem like a dumb question but I would like to use my old Tach/Dwell meter under my hood to simply read my idle RPM. It's been at least 30 years since I have used it (had Electronic conversions a long time), and I'm not certain exactly how to connect it. It has just the two wires. I assume it connects to the coil, but I don't want to take any chances. Also, I'm not certain it will work with my Pertronix II conversion.

Thanks for any help.

Stu Fox

[Harry S.]

Re: Use of old Tach/Dwell meter

I used mine last week after the same amount of time. Red wire to the distributor side of the coil and black wire to ground. I don't know why it would not work, it's well before the points/electronics.

[Bruce B.]

Re: Use of old Tach/Dwell meter

MVC-026S.JPG

Stu,

My vintage 1982 Sears Dwell Tack shows the black wire to ground and the green wire to the negative (signal) side of the coil. Ignore green to battery positive, it's for voltage testing.
It works fine on my old Pertronix 1 with a GM coil.

See attached picture.

[Stuart F.]

Re: Use of old Tach/Dwell meter

Thanks Harry and Bruce. I feel more confident now. Will give it a whirl this week end when I do some more carburetor tests. I just hated having to go look in the driver's side window to check my idle speed.

Thanks again,

Stu Fox

[Tom R.]

Re: Use of old Tach/Dwell meter

Not only do I have my tach/dwell meter from that period but came across the user's manual this past summer. I could scan and post (if I can find it again) if it would be helpful

[Stuart F.]

Re: Use of old Tach/Dwell meter

Tom;

That would be great if you could do that. Never can have too much information on how to use something, specially for us old gezzers. Thanks.


Stu Fox

[John H.]

Re: Use of old Tach/Dwell meter

Stu -

I've had my dwell meter for almost 50 years; the red lead goes on the (-) coil terminal (distributor primary wire), and the black lead goes to ground. Chrome-plated solid die-cast housing, and thick glass lens on the meter - they don't make 'em like that any more.


DwellMeter650.jpg

[Stuart F.]

Re: Use of old Tach/Dwell meter

Thanks John for the reply and photo of your meter. Looks a lot like mine, but perhaps a bit better quality. I'll see how mine works this weekend. Wife is out of the country for a few weeks so I got lots of time to play. I just spent the morning in a big Hobby store; got me a new "complete" set of number drills and a new pin vice with two chucks. Got to correct some new jets that were supposed to be .104", but measure a tad over .101". What ever happened to quality control? These were from Carbs Unlimited out of WA. Their metering rods are not too good either. Have to buy several pair to get a match. I trust my old micrometer more.

Stu Fox

[Stuart F.]

Re: Use of old Tach/Dwell meter

Just as a follow up on this issue; I tried using my old Tach/Dwell meter the other day and found the tach portion, for which I resurrected this instrument for, was reading about 150 to 200 RPM less than my cable driven dash tach. When my dash tach showed 750/800 RPM, the meter tach showed 600 RPM. When I disconnected and plugged my VAC line to set my timing, my dash tach dropped to about 600 RPM, and the meter tach read 400/450 RPM. Now, for any doubters; I've lived with my 63 L-76 long enough to know that it will not idle down to 400 RPM and still continue to run.

The meter appears to be ok otherwise, i.e. the needle is set to zero, etc. Therefore, I have to question whether it will operate correctly with my Pertronix II ignition conversion. I connected the red clamp to the negative terminal on the coil (black line from the distributor) and the black clamp to a conventient ground on my intake manifold. Understand, I do run a 12 volt input to the Pertronix unit (no resistor) as that's what it calls for.

I really would like to have the unit available for use on under the hood RPM checks, but for now it goes back in the box and on the shelf for another 30 to 50 years.

Stu Fox