Aftermarket Tachometer Question

[InTheDogHouse]

Hi All,

Looking at a Stewart Warner electrical Hall Effect tachometer. Says it has 0.5, 1, 1.5, 2 ratios. With my 1987 6.9L NA E350 WHERE does it mount and what ratio do I need? Thanks for any and all help!

 

[punkmechanic]

I just did a little research on hall effect tachs and from what I found they use a magnet on the object being measured (in this case the crank, flywheel, or crank pulley) and the sensor "sees" the magnet and relays the signal to the tach.

that said you would have to mount a magnet a set distance from the sensor on something that rotates at crank shaft speed.

The 0.5, 1.0, 1.5, and 2 ratios are for mounting the magnet on different pulleys or drives from the crank. For instance, the crank turns twice for every camshaft revolution. Therefore if the magnet was on the cam to get engine rpm you would need the 0.5 ratio so the gauge would read double what the sensor said.

I would think for easy of installation you should look at autometer or isspro and see about the tachs that read off the alternator. I have never seen one in person but from what I understand its basically a strap that goes around the alternator and reads the varing magnetic field it creates with higher and lower rpm ranges.

That or find a gauge cluster with a tach in it and a sender from the local salvage yard, should be a plug and play.

punk

 

[InTheDogHouse]

Ah, so I'm going to mount the sending unit on the crankcase near a pulley and put the magnet on that pulley. Then measure the pulley and if its the same diameter as the crankshaft pulley = 1:1 ratio. If the pulley is 1 1/2 times as big = 1.5:1 ratio. If its 1/2 the size = 0.5:1 ratio. Sound right?

Would look at tachs from the junkyard except they mostly read 0-8,000 rpmish. I really like the 0-3,500 or 0-4,000 diesel tachs.

Looking at tachs on Ebay to try and save. Hence having to learn WHAT I'm buying and how it works before the bid. Thanks again for your help.

P.S. Just curious, but with a C6 tranny how do I find out what rear end I have and then calculate MPH and RPM for each gear. If this tach thing gets too expensive I don't mind using the speedo as a reference to RPM.

 

[Pearl_Diesel]

Your injector pump housing should have a port in the top near the oil fill where the factory Tach sender goes in, just unscrew it and put a factory tach sender in there.

 

[Pearl_Diesel]

Any factory tach sending unit from the IDI's will work, 83 6.9 all the way to 94 7.3 turbo

 

[zacky6661]

Any factory tach sending unit from the IDI's will work, 83 6.9 all the way to 94 7.3 turbo

so all i would have to find if i were to install a tach is just the sender? mine came with no tach. then where could i get a guage?

 

[GenLightening]

so all i would have to find if i were to install a tach is just the sender? mine came with no tach. then where could i get a guage?

Wrecking yard, though they can be hard to find. And make sure to get the circuit board off the back of the cluster, otherwise you'll need to wire it your self (not too difficult).

 

[bike-maker]

I've been looking for a factory diesel tach for a 83-86 at the JY's for over a year with no luck. I think I'll have to go a different route. Another thing to consider is whether your front cover has the provisions for mounting a sensor. Some don't.

 

[Agnem]

Any factory tach sending unit from the IDI's will work, 83 6.9 all the way to 94 7.3 turbo

Not quite. The tach was not available until 1985. You will not find a tach in an 83' or 84' from the factory.

 

[seawalkersee]

Dakota digital has an adapter that will make the factory gasser work with the diesel engine. It is $120ish and mounts through the bell housing and goes off of the teeth on the flywheel. There are a few discussions on here about it. I will find the links for you.

SWS

 

[seawalkersee]

http://www.oilburners.net/forums/showthread.php?t=26060
There is one of the links I found. There is another one with the link to the parts (or some parts like) in the pics. I have found SEVERAL e-bay items that make it appear if it will work. I have not had the scratch to make it work in mine yet...and it does not run because of the same problem.

SWS

 

[FordGuy100]

I run an ISSPRO tach on my A-pillar. Glue two magnents 180* off on the harmonic balancer, secure a sensor so it can pick them up, and wire it up. Works really good, and I would say its accurate to within 25rpm's or so.

That was actually the first thing I ever did to my truck

 

[zacky6661]

Not quite. The tach was not available until 1985. You will not find a tach in an 83' or 84' from the factory.

just realized that. looked near my oil fill and theres no spot for the sender to screw in. Mel, or Justin, whats the product number for the isspro tach i see alot floating around here, i saw a number but when i searched the isspro site, it came up product does not exist

 

[GenLightening]

If you need a housing, I have for the 6.9 with the sender hole.

 

[Agnem]

That's the best bet. Get the good housing. Don't fear... I have a technique you can use to swap that housing out without loosing your gear timing.... Either that, or build yourself a tach like I did. Mine is optical and works off the flywheel. It has been rock solid for 26 years.