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Discussion Topic:
Dwell/Rpm Meter
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mzahorik |
08-10-2021 @ 11:09 AM
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Member
Posts: 209
Joined: Nov 2009
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I have my 1937 rebuilt engine running pretty good. The thermostats and temp gauge are working. I have good oil pressure and vacuum. I was wonder whether or not my negative ground Dwell/RPM meter will work on this positive ground car. This is my 1st + ground car, or do I need something special. Thanks Mike
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mzahorik |
08-10-2021 @ 3:20 PM
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Member
Posts: 209
Joined: Nov 2009
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Well..... I gave it a try and my 40 year old Sears and Roebuck ,meter did not work. So I disconnected the coil wire and powered the ignition from a separate battery and this seemed to work. So only the ignition worked on negative ground. I got a dwell of 38 degrees and an RPM of 1000. I thought it was a little high. Turned it down to 700 and the engine seems fine. Maybe I should look for a meter that will work on + ground. Mike
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JayChicago |
08-10-2021 @ 6:14 PM
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Member
Posts: 492
Joined: Jan 2016
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My forty year old Sears dwell meter/tach works. Proper polarity is required for the meter to read properly, so connecting to the car is opposite of what you are used to. Red+ meter lead goes to ground on the car, black - lead to coil.
This message was edited by JayChicago on 8-10-21 @ 6:19 PM
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sarahcecelia |
08-11-2021 @ 4:52 AM
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Senior
Posts: 1194
Joined: Mar 2013
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These motors are supposed to idle at about 475-500 RPMS.
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TomO |
08-12-2021 @ 7:57 AM
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Senior
Posts: 7264
Joined: Oct 2009
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You did not explain where you connected your dwell meter, or what distributor and coil you are using. This makes any answer to your question a guess. Do you have the original 1937-1941 helmet distributor? Are you using an original type coil, mounted on top of the distributor? If you are using a 49-55 Ford coil, do you have it wired with the + terminal going to the distributor?
Tom
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mzahorik |
08-16-2021 @ 11:02 AM
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Member
Posts: 209
Joined: Nov 2009
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I have the original 1937 distributor and coil. The dwell meter is connected to the positive and negative power and the sense lead is connected to the capacitor on the side of the distributor (to ge at the points).
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TomO |
08-17-2021 @ 7:45 AM
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Senior
Posts: 7264
Joined: Oct 2009
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Mike, You may have one of the Sears "electronic" engine testers. These will only work on negative ground systems and the user's manual specifies this. If your meter is accurate, your dwell is too long. It should be 34-36 degrees. the correct idle speed is 450-500 RPM.
Tom
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mzahorik |
08-19-2021 @ 1:15 PM
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Member
Posts: 209
Joined: Nov 2009
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Thanks Tom. I don't think the meter is accurate, but it tells me that I'm in the ball park. AND the engine is running fine. I think I'll look for another meter that will work on both + and - ground. Mike
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