I know it's probably electrical noise, but I've wired up this tach I picked up yesterday (new, aftermarket) strait to the battery + and - terminals, and the coil-side -, and it still jumps as soon as the engine goes about about 1,200 rpm. It seems to work well and fine below there, increases steadily to 1,200 and then just decides to start guessing at the rpm and jumps between 2,000 and 7,000. Any ideas? Bad condenser or something distributor side maybe?

I would reread the direction closely and pay close attention to the distributor applications. If you don't find anything relevant then call the manufacturer.

I think it's unlikely that I've missed a step in the install Jim. Aside from girlish hand strength, I am fairly competent when troubleshooting stuff. I'll link the install guide, but essentially the install steps boil down to:

Black to ground
Red to BATT on Run
Green to Coil -
White (optional) to Dimmer

Even the test mode, to just verify the thing works, says to attach to battery + and -, and coil -. I had it connnected as recommened before, but decided it had a bad/noisy ground so ran the black to battery -, but it's still jumpy.

(Forgot to include link: Tach Install Guide )

What I was thinking was of the compatibility of the tach to your set-up, not a mistake you made. I would call the manufacturer.

My tach did that and turned out to be the actual coil.

if you don't want it to jump;try cutting it's leggs off.lol

I think Jim hit on the problem. Different tachs work off different types of signals. Like the MSD box I just put in says it puts out a square wave signal. I'm not sure how many different types of signals there are but it looks like I have to buy an adapter that changes it to something else to run my original tach off it. Check out the install instructions on their site it covers a little bit about tach hook ups.

Robert

Robert, your MSD doesn't power your hood tach correctly?

[quote=Luminous]
Black to ground
Red to BATT on Run

I'd avoid running wires directly to the battery. Try to hook the RED to an open clip on the fusebox that is only hot when the ignition is engaged, and properly ground the Black to the car frame using an available grounded screw or bolt.

Does the RED wire have an inline fuse?

I just got out there today and tried to hook up the tach a couple of different ways. Turns out the tach terminal on the MSD box was the ticket. Evidently sends the correct type of signal to run my stock in-dash tach. Very cool. Color me happy.

Robert

I lied and have the tach hooked up to a Run Hot clip on the fuse box. There is no fuse inline on the red wire to the tach. I guess I'll get in contact with Sunpro and see if they have any idea, though I'm not totally against putting a HEI/Ignitor in with a new coil and seeing how that works out.

Marine, don't replace working ignition parts just to get the tach running. The tach is not required to drive that car of yours.

As a lessons learnt for your books: I ALWAYS splice an inline fuse assembly into any hot wire going to the fusebox or the battery.

Most electric components (stereos, amps, tachs, aftermarket lights, etc) require it based on operating amperage requirements. It may be redundant protection in some cases but it is safer to err on that side.

In my humble (blown a few electric parts in the old days) opinion.

Thanks for the advice John, I didn't think that the tach would pull that much of current though, and since the manufacturer didn't supply an inline fuse I never thought about it.

The tach isn't so much for looks as it is function, and at this point in the project it's a troubleshooting device. But of course, this troubleshooting device needs troubleshooting. An ignition upgrade was something I had planned on doing down the line, so it's not that I'm thinking of spending $300 to get a $30 tach to work, but if it also solved that problem, then I could see moving it up a few spots on the To Do list.

While the car does start and (used to) drive, some of the stuff I've seen done to this car make almost every system suspect to me, so replacing the ignition with at least an Ignitor doesn't seem to be too crazy to me. Especially when the last time I messed with points and condensers was with my '77 GS550, and that was coincidentally the last time I ever wanted to mess with points and condensers.

And I'm not sure how to read this one, maybe you guys can help me. But when I finally got the trunk open, I found 2 distributors in the back. Not one mind you, 2 full distributors (well minus caps). So I think that leads me to doubt the quality of the ignition system just a bit more.

If one of those distributors happens to be a 1111946...

I'll check next time I'm out there. I know I glanced at them before but didn't notice any numbers, where exactly are they located?

Also, is there some kind of reward for having the longest posts, because I'm thinking I could be in the running.

The numbers are stamped on the largest part of the distributor body.

Semper Fi, when I first got my 68 bird, I made a to-do list that was three pages deep, single spaced!! I still have that hand-written list and keep it in my envelope of important car paperwork for this bird of mine. Its a great historical car document in my opinion, and tracks jobs done and parts teplaced by date and source.

So, keep all those doodle lists and plans sheets for historical purposes.

Luminous, just installed Ignitor II and 6AL MSD box in my '68. Quite a fun project full of challenges along the way. Plan on spending about $350. These things never seem to go like it does when you watch these DYI shows on the Speed Channel. I'll be glad to assist you with this fresh knowledge. But, it won't be fresh long...I'm almost as old as Nash!!!

Greg, you and I are two of the youngest folks here!

I'm betting I'm half your age though . And just so you don't think I forgot Vikki, the distributers are numbered 1111253 and 1112008. Sorry I couldn't come through for you.

If you want to sell the 1111253, I'll take it!

I'll let you know just as soon as I am able to ship stuff out, which is probably about 6 weeks away.

Just for info, they are re-making those distributors with the stamping and date you want on them. It was a big deal on the Camaros. At one point, they used the distributor number to help document the car. Not any more.

I like to keep a couple of similar originals on hand, set up and ready to drop in. With 40 year old parts that rotate 90,000 times an hour on average, they're bound to have a little wear on them. And by having a couple of different profiles, I can easily experiment with advance curves and pulloffs.

The obvious question would be: "Why would you care about numbers then"?

Because if I pick the right numbers the distributor will already have the curve I want and the correct hardened drive gear. Call it laziness if you wish...