Tach hook up - Ford Truck Enthusiasts Forums

1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck

Tach hook up

Thread Tools Search this Thread
Old 09-27-2013, 02:06 PM
264WSM 264WSM is offline
Senior User
Thread Starter
Join Date: Dec 2011
Location: Wyotana
Posts: 188
264WSM is starting off with a positive reputation.
Tach hook up

Not exactly a Ford question but I need help with my thought process.

I have an old Case Back-Hoe (that I pull w/ my Ford) that I want to put a Tach in. It has a 4 cyl gasoline engine that spins to 2300rpm. The tach I have goes to 8000, so trying to look at 1500-2200 will be difficult. However, the tach has a switch on the back for 4-6-8 cyl engines. If I install this and put the switch on 8, will it read 4600 when I am actually doing 2300rpm??
I want my max rpms to read around 60% or so of the face. I can "recalibrate" the face with a Sparpie marker.
Reply With Quote
Old 09-27-2013, 05:43 PM
fmc400's Avatar
fmc400 fmc400 is offline
Join Date: Apr 2004
Location: Austin, TX
Posts: 10,386
fmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud offmc400 has much to be proud of
RPM is proportional to the frequency of the switching waveform at the coil, call that FREQ, measured in cycles per second (Hz). For a 4-stroke engine, RPM = 120 * FREQ / CYL where CYL is the number of cylinders (4, 6 or 8). For a given frequency, RPM decreases as the number of cylinders increases. Therefore, 2300 would appear as 1150 if you set the switch to 8. The 4-cylinder setting is the highest you'll get.

You could just do like I did, and build your own homemade digital tachometer

Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
94 ranger question rebnutt Ranger & B-Series 2 10-25-2016 02:29 PM
no tach for vans? carsronnie86 1994.5 - 1997 7.3L Power Stroke Diesel 8 05-24-2016 05:22 PM
4.2 tach addition Josh Picard 1997 - 2003 F150 2 05-17-2016 08:41 PM
new Style Tach issues MIKES 68 F100 1967 - 1972 F-100 & Larger F-Series Trucks 4 10-30-2015 01:10 PM

Go Back   Ford Truck Enthusiasts Forums >

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

All times are GMT -5. The time now is 03:21 PM.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.