A simple tester for original Tachometer

MSD in these circles stands for Might Suddenly Die. So be forewarned.

The original dual point distributor is a very good unit but if you want to upgrade to solid state, then the Ford Motorcraft is a much more reliable solution teamed up with a Pantera-electronics engine ignition controller.

That as considered as a unit is all plug-n-play and provides for the tachometer connection without an MSD adapter.

If you are here looking for advice, I'm just reflecting upon my 40 years of Pantera ownership and 55 years of Ford performance cars.

You didn't ask specifically this question but I consider it a synonym. A word that is not exactly the same but similar. I feel the question coming.

I like your testing method, it is clever, but in addition these tachs are showing a need to be cleaned and often need to have the jewel movement of the needle lubricated. It's just their time to show it around now. The two that I had tested were off about  350 rpm and needed to be calibrated also. Pantera-Electronics can check the tach and calibrate it for you.

There has been quite a bit of discussion on this forum on subjects that all revolved around the distributor and ignition upgrades. If you are data driven, you would be wise to consider what I say but then again, I'm not highly intelligent, just highly experienced and my mistakes have yet to be lethal.

Tach amps are available, and necessary to use your Veglia with a modern ignition (that may only output 12v).  Here is much cheaper... https://www.ebay.com/itm/142171581596

Or, you could be crazy like me and retrofit a modern stepper tach into a Veglia can...  https://pantera.infopop.cc/top...93#19905352128593293

...geez, I had a lot more time on my hands then...and as predicted, it sits on the shelf and another in the car...

The eBay adapter does not work for Panteras ...  Below is from their eBay listing.

The BTAC2 can NOT substitute for the MSD 8920 in applications with current-mode tachometers, such as pre-'74 Mustangs and Pantera Veglias

...oh, time to try mine--I bought one of the BTAC2 and its still in the box. But the Veglia isn't a current triggered tach--and even, when I wrote "modern ignition" I meant the Fiat/Pantera/Alfa Veglia needs the tach amp when driven by a "tach output" from an ignition box (but if connecting to the negative terminal on a coil, the Veglia won't know the difference between points or a transistor...).  I have no idea about the MSD8920..just wish I had a clue 25 years ago when I put the Electromotive ignition on my 308 and then forever missed having a working tach....Lee

Everything Doug said about the Ford electronic distributor is correct and I will add that a solid state Ford TFS coil truly makes the system bullet-proof. This e-coil replaces the can-of-oil coils used since the flathead days. The TFS has an odd multi-wire power plug, but inside the coil's molded top is a pair of common spade lugs marked + & - so hookup to your Pantera wiring is simple.

If you drive in wet weather, plug your wires in, grease the inside of the coil opening and fill the cavity with RTV. The grease will prevent RTV from bonding to the coil so in effect you've made your own weather-resistant removable plug.  Otherwise you can collect rainwater in a vertically mounted  coil's cupped opening, with unhappy results. Or mount it upside-down.

Note that MSD uses Ford weights and springs inside their distributors- the only parts they contribute is the electronics- which fail often. The 'touchy' part is, Ford made hundreds of variants of their dizzys and Clevelands use the plug-in electronic model off a 429/460 TRUCK, which usually gives you a truck ignition advance curve. Have your e-dizzy recurved for a performance sports car.

(I couldn't help myself, I sent a message to the Ebayer (Gene) who makes that signal amp, including a schematic of the Veglia tach-- he replied that they hadn't tested one themselves, but their interpretation of the connectors (esp, noting a "-" and "+" pin suggested that it was a current-triggered amp--when in fact, the signals are Battery (+), the middle post is ground, and the final pin is the signal (and if I remember correctly, Fiat 850/124 tachs don't have the post connector and maybe sequence differently, but the same circuit board is used on everything no matter 4 or 8 cylinder or for a Harley).  For real geeks, the proof of a voltage triggered tach is the C4 cap in front of the Q1 transistor...

for just $8 shipping to New Zealand, maybe you can be the one who can confirm to Gene that it really works I have some time coming up (Chinese New Year just 2 weeks away) and I'd love to pull my pieces from the closet and test myself...! 

Hi Lee

Yes just looking at the schematic you posted I see there are 2 resistors in series after the input (2,200 ohms and 2,700 ohms) this would confirm it's voltage triggered. Also the fact the breaker point input comes from the  ' -  ' coil input is confirmation it's voltage triggered. I'm an electronics guy so after I get my car finished I'll have time to help analyze this and other circuits. I hope Panteradoug forgives me but I can't go back now I have the Billet MSD distributor, 6AL ignition control and PN 8920 Tach Adaptor. No doubt a totally unreliable package in Doug's eyes but we will see. I will report any problems. The motor is in the car but before installing it I ran it and broke the cam in on a test stand. So the MSD ignition is going ok so far. I have a cheap tacho on the test stand and it didn't work with the MSD so maybe I should get one of Gene's adapters to try on that.

Cheers

Ross

Ross, maybe in a couple weeks, I'll see if the function generator is still in the closet, find that tach amp that I bought, and see if the Maserati tach I bought for whatever reason (I think from an Indy...what a lovely thing and the same physical size as the Goose/Pantera tach) actually works.

  Since we're both electronics folks, I'd be curious if the MSD needs an external pullup--at least, it would have been a really safe thing for MSD to just have an open-collector output so somebody connecting anything wouldn't damage the output... but probably, we just don't need to know Lee

After all the chatter regarding MSD ignition un-reliability, while its all true, I've never heard of the #8920 tach adapter failing!

I have had several of the MSD 8920 Tach Adapters fail.  After burning out a couple of them, I researched the issue and MSD explained that charging the battery can sometimes fry the unit.  After reading such, I began disconnecting the battery ground cable when charging.  I figured that if charging the battery can damage the 8920, then other electrical components might be at risk.  I have not fried an 8920 since then.

My Pantera project that I received early last year might have a fried 8920.  The tach is not working but I have not started isolating the problem yet.

Well that's at least some good news for me bosswrench. I don't think the distributor will be a problem either, after all it's just a hall effect transistor with a magnet running around it. I actually think a lot of problems with electronic equipment that requires installation is due to shoddy workmanship and poor knowledge and understanding of the basics of wiring. Reminds me of a time early in my career when I built my first amplifier, ran fine on batteries but hummed like hell when I connected the mains source power supply. I sold it to my boss and he had it running in 5 minutes. All down to my lack of understanding of  earthing and grounds. I've learnt a lot since those days.

Cheers

Ross

Hi Steve

Those 8920 units that you fried will not happen in my car because I have fitted a cut off switch near the battery in the front trunk. With this switch turned off all the power to the rest of the car is isolated and it is safe to hook a charger to the battery without removing any leads from it. It's also an intended security system as I'm going to make it hard for any potential thief to find the opener for the front trunk. As a side note a lot of chargers send out a fairly raw pulsating DC, which electronic circuits don't like very much.

Cheers

Ross