The Ford Barn

IndyA · 09-07-2017, 07:38 AM

I have an old Tachometer (actually also measured dwell & point resistance) that I used on a Negative ground, V-8 auto...has two alligator clips; one red the other black and has analog scale for 6 cylinder & 8 cylinder readings. Can I use this on my '29 A and divide the 8 cylinder reading by 2? ... If "Yes" can one of you experts tell me how to hook it up??? Many thanks for your help.... IndyA

Jim/GA · 09-07-2017, 08:24 AM

Yes! I do it all the time!

If your Model A is still positive ground, connect the red clip to ground and the black clip to the wire coming off of the coil that eventually makes it's way down to the points. On stock Model A wiring, that's the red lead off of the coil.

That's it! Double 8-cyl. engine readings for a 4 cyl. engine. That is, if the 8-cyl. scale reads 200 RPM, that is really 400 RPM on a 4-cyl. engine.

katy · 09-07-2017, 10:09 AM

On my old 6/8 cylinder dwell/tach meter it says to multiply (not divide) the 8 cylinder reading by 2 to get the 4 cylinder reading.
Which is correct?

Keith True · 09-07-2017, 10:40 AM

My old tach/dwells all say to double 8 cylinder readings for 4 cylinder engines.

Jim/GA · 09-07-2017, 03:51 PM

Yes, of course, double for 4 cyl. I can never remember doing it from memory by I know what to do when the tach is in my hand.

I aim for about 200 rpm and about 20 degrees of dwell on the 8-cyl. scale. Double them to get the 4 cyl. numbers.

mike657894 · 09-07-2017, 04:28 PM

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i had 3 from garage sales. they all read differently i deiced the one that looked to be in the right area to be the most accurate.

Tom Wesenberg · 09-08-2017, 03:00 AM

Quote:

Originally Posted by mike657894

i had 3 from garage sales. they all read differently i deiced the one that looked to be in the right area to be the most accurate.

I've had the same thing with the cheaper meters.

09-07-2017, 07:38 AM	#1
IndyA Member Join Date: Dec 2016 Posts: 61	Can I use 50yr old Handheld Tachometer ?? I have an old Tachometer (actually also measured dwell & point resistance) that I used on a Negative ground, V-8 auto...has two alligator clips; one red the other black and has analog scale for 6 cylinder & 8 cylinder readings. Can I use this on my '29 A and divide the 8 cylinder reading by 2? ... If "Yes" can one of you experts tell me how to hook it up??? Many thanks for your help.... IndyA

09-07-2017, 08:24 AM	#2
Jim/GA Senior Member Join Date: May 2010 Location: Young Harris, GA Posts: 1,821	Re: Can I use 50yr old Handheld Tachometer ?? Yes! I do it all the time! If your Model A is still positive ground, connect the red clip to ground and the black clip to the wire coming off of the coil that eventually makes it's way down to the points. On stock Model A wiring, that's the red lead off of the coil. That's it! Double 8-cyl. engine readings for a 4 cyl. engine. That is, if the 8-cyl. scale reads 200 RPM, that is really 400 RPM on a 4-cyl. engine. __________________ Jim Cannon Former MAFCA Technical Director "Have a Model A day!" Last edited by Jim/TX/GA; 09-07-2017 at 03:53 PM. Reason: "double", not "divide by 2"

09-07-2017, 10:09 AM	#3
katy Senior Member Join Date: Jun 2015 Location: Red Deer, Alberta Posts: 5,046	Re: Can I use 50yr old Handheld Tachometer ?? On my old 6/8 cylinder dwell/tach meter it says to multiply (not divide) the 8 cylinder reading by 2 to get the 4 cylinder reading. Which is correct? __________________ If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn!

09-07-2017, 10:40 AM	#4
Keith True Senior Member Join Date: May 2010 Location: Epping N.H. Posts: 2,989	Re: Can I use 50yr old Handheld Tachometer ?? My old tach/dwells all say to double 8 cylinder readings for 4 cylinder engines.

09-07-2017, 03:51 PM	#5
Jim/GA Senior Member Join Date: May 2010 Location: Young Harris, GA Posts: 1,821	Re: Can I use 50yr old Handheld Tachometer ?? Yes, of course, double for 4 cyl. I can never remember doing it from memory by I know what to do when the tach is in my hand. I aim for about 200 rpm and about 20 degrees of dwell on the 8-cyl. scale. Double them to get the 4 cyl. numbers. __________________ Jim Cannon Former MAFCA Technical Director "Have a Model A day!"

09-07-2017, 04:28 PM	#6
mike657894 Senior Member Join Date: Oct 2015 Location: Bay City Michigan Posts: 1,050	Re: Can I use 50yr old Handheld Tachometer ?? Sponsored Links (Register now to hide all advertisements) i had 3 from garage sales. they all read differently i deiced the one that looked to be in the right area to be the most accurate.