TACH ON DIESEL MODEL TRUCK

[echo7bravo]

They did come with a tach as an option even on the 350 Olds Diesel. The diesel tachs drive off pre-diode AC from the alternator. If it's a diesel tach it wont have the right calibration for V8 or I6.

My bother said the same thing. He said that after we get the truck all put back together he would have his speedo guy calibrate the tach and check all the other gauges.

At least I don’t have to worry about trying to pull them or do myself.

 

[Eriknor]

Thanks for the input all the way from Norway. I guess you'd know since you have a 6.2 in yours. I wasn't sure how the diesel got the signal myself.

The gas HEI tach lead just counts coil fires and divides by 8.

Just nice too help

 

[hatzie]

My bother said the same thing. He said that after we get the truck all put back together he would have his speedo guy calibrate the tach and check all the other gauges.

At least I don’t have to worry about trying to pull them or do myself.

The meter portion is the same on all of em... The Diesel PC board has different components for handling the AC waveform from the alternator.
Wilcox Corvette used to have a replacement PC board for smallblock V8 HEI squarebody tachs. If they still sell it that's the easy way to re-vamp your tach.
It's worth noting that the diesel tachs have different graphics from the smallblock tachs. The Big Block and Inline 6 tachs may be different as well.

 

[echo7bravo]

The meter portion is the same on all of em... The Diesel PC board has different components for handling the AC waveform from the alternator.
Wilcox Corvette used to have a replacement PC board for smallblock V8 HEI squarebody tachs. If they still sell it that's the easy way to re-vamp your tach.
It's worth noting that the diesel tachs have different graphics from the smallblock tachs. The Big Block and Inline 6 tachs may be different as well.

How were the graphics different?

You must be registered for see images attach

 

[hatzie]

I've seen 4K, 5K, & 7K tachs with several different red-lines.
The diesels in the MD trucks redline around 3K-3.5K. Never looked at a Light duty diesel tach but they do exist.
The actual meter movement is the same part. The circuit board determines how far the needle moves per rev. The graphics are painted to match.

You must be registered for see images attach

 

[highdesertrange]

ooooo I like that dash. highdesertranger

 

[Eriknor]

You must be registered for see images attach

Lmctrucks have new tachometers: http://www.lmctruck.com/icatalog/CSB/full.aspx?page=93

 

[Honky Kong jr]

Camaro tach......there was a good write up on here but I think most of the pics evaporated after the whole photofukit ********.

 

[bucket]

How were the graphics different?

You must be registered for see images attach

It's been a while since I looked at it, but I'm pretty sure that's exactly what my '77 K5 gasser tach looks like.

Camaro tach......there was a good write up on here but I think most of the pics evaporated after the whole photofukit ********.

Another good option. And you can also install a matching 85, 115, 140 or 145 mph speedo.

 

[Honky Kong jr]

It's been a while since I looked at it, but I'm pretty sure that's exactly what my '77 K5 gasser tach looks like.



Another good option. And you can also install a matching 85, 115, 140 or 145 mph speedo.

Definitely. I know there are plenty of articles out there. I’ve seen the retroed for sale to pop right in salty lil bastards though.

 

[echo7bravo]

Were going to wire everything up this weekend and get it running. I curious to see how far off it is.

But, no worries. Brother in law is going to take it to his speedo guy and have everything checked and calibrated once we get it moving under it’s own power.

 

[hatzie]

GM showed what's inside the Tach filter cans in the 1983 wiring diagrams.

1- 100pF capacitor
1- 0.15μF capacitor
1- 5.6KΩ resistor
1- 10KΩ resistor

The Caps don't note any polarity so I'd use Radial lead Poly caps rated for around 50vdc. You can use Electrolytics but why bother... the Poly caps should do the job and they will last darn near forever.
I'd use 1/2W metal film resistors. Wirewound is more expensive and will have the additional variable of x number of micro henrys of inductance. The inductance may not bother the tach but again why bother when the cheaper metal films will do the job. Cheap carbon resistors don't live long in high temp, high vibration, highly variable humidity situations.

You must be registered for see images attach

 

[HotRodPC]

ooooo I like that dash. highdesertranger

I'd like it better if the tach read higher than 4,000 rpm. I like the dashes sometimes found in C60's where they have gas tach up to 6000 rpm and the fuel gauge, then a Vacuum gauge where the clock goes.

 

[CORVAIRWILD]

I have a tach-fool gauge from a '77 C60 8.2 diesel I scrapped. I'll post an image of I remeber to go look at it

 

[hatzie]

I have a tach-fool gauge from a '77 C60 8.2 diesel I scrapped. I'll post an image of I remeber to go look at it

So there are 4K, 5K, 6K & 7K tachs...
Plenty of variables in the wild.