I have an old Sears Dwell/Tach Meter (tune-up tool) that was used on the old American cars for checking dwell angle (points) or engine RPM. There is a switch for either 8/4 cylinder or 6 cylinder for RPM if I remember correctly (I have not looked at it in over 10 years). Can this meter read RPM on B23F engine? Will it damage the electronics on the car? Is it hooked up the same? One lead to coil, the other to ground? Thanks for your input.

I have the same meter. After all these years it still works great. I always use it to fine tune the RPM's and to check the dwell on the Lambda Sond System. Enjoy your new (old) found toy.

Sincerely,
--
Nickvjr

1979 264GL B27F 121K

Features Added:

BW55 To M46, Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

Add Cruise Control

If it's like my old Sears dwell/tach (no specific setting for 4 cyl) set it for 8 cyl and divide the RPM by 2.
I checked that old meter against a DVOM recently and it's still accurate.
--
'80 DL 2 dr

"I checked that old meter against a DVOM recently and it's still accurate"
How does one check a tach/dwell meter?
--
1980 245 Canadian B21A with SU carb and M46 trans

Check it against reading taken with another instrument that you know is accurate.
--
'80 DL 2 dr

You said you checked it against a DVOM. I interpreted DVOM to be short for digital volt ohm meter (ie. multimeter). My mistake?
--
1980 245 Canadian B21A with SU carb and M46 trans

No mistake. That's what I meant.
--
'80 DL 2 dr

Trev,

I think he has an automotive DVOM that has Tach and Dwell/Duty Cycle functions, in additon to the usual Volts/Ohms/Amps.

I have one by "Sun Pro" that was about $60 a few years ago at Pep Boys. Probably cheaper ones around by now.

Bruce
--
Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted only 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67

I was using a borrowed Fluke 79. I think that's what it was. More expensive than what I would need. I would like to buy an automotive digital meter. If anyone reading this knows of a bargain price on one please post the info.
I was using the Fluke to test the lambda sensor and the duty cycle of the frequency valve. After having adjusted the air flow meter to return a value of 50% I checked it again with the 30 year old dwell meter just to see if it was still working properly. It gave me a reading of 45 degrees. It still works. So I figure the tach function is still dependable too.
--
'80 DL 2 dr

"I think he has an automotive DVOM ..."
Okay, thanks. I thought that maybe there was a way to use a multimeter to check considering my tach/dwell meter is so simple to hook up.
--
1980 245 Canadian B21A with SU carb and M46 trans

"Can this meter read RPM on B23F engine?"

Yep, works fine.

"Will it damage the electronics on the car?"

Nope.

"Is it hooked up the same?"

Yep. Connect the black meter lead to ground and the red meter lead to the (primary) side of the coil that's connected to the ignition module. (The other primary side is connected to 12 volt power when the key's on.)
--
Don Foster (near Cape Cod, MA)

Yes, low side of coil to ground. The dwell function can be used to check frequency valve duty cycle. I think the manual says it should be around 5o-60 degs.

Just saw that in the Bentely yesterday.