lateapex911

Hello,
Just got my old 911 back running, and I am a happy man. Thanks to some kind folk here and over on the Pelican BBS. I had a blown Bosch CDI box, so I have replaced it with an MSD 6AL, and the points with a Crane optical trigger.

After much troubleshooting I have it running. (My choice of a 'Batt" source was not up to snuff. When i attached it to the source side of the fuse, viola! consistent spark)

The question now becomes, how to get the tach running? the old dizzy had a purple black wire that the wiring diagram shows going to a "speed switch". German for tachometer?? the MSD has a tach out, but they recommend their tach adapter. And of course there's the white trigger out from the Crane unit, but they warn that it's really not strong enough to do much of anything. And I can see why!

And I remember reading somewhere that I need to be careful, or I'll blow my tach up. It already bounces all over the place, but I don't want it to never bounce again!

So...what is the consensus? How best to get it reading again?

Thanks again,

Zeke

I think the story is the same as on the 914. Didn't you used to have a 914? Anyway, get the tach adaptor they recommend.

MRFLATSIX

You need the MSD tach adapter to make it work. I believe it's the model 8920.
I have a '70 with MSD and the adapter will fix the problem. The other thing you need to do is make sure you have really good power and ground connections. This is where guys get into trouble with these ignitions. Run a 12 gauge wire from the battery terminal on the starter to power you MSD. Taking it from anywhere else doesn't give you enough current. Make sure your connections are tight. I don't know where the ground stud is in your engine compartment, it's on the left side on my '70. At any rate make sure it's clean and tight. Don't cut corners. Do it right and it'll work great. I've used the Crane optical points replacement and it's works very well and is very reliable if you can get past the Mickey Mouse insallation.

lateapex911

Thanks....no 914 here. I had an old Alfa spider with weird fuel injection...and an old '67 Camaro SS/RS convertible, but that's it for cars with a good view of the sky....

lateapex911

Man you hit the nail on the head ! I pulled it out of the package and thought, "sheeesh!...could it be any cheesier??" And getting it to fit in there was a bit of a trick. Very tight. And the screws that hold the bracket to the sensor hit the window wheel if you put the sensor in a position where it doesn't hit the cap! and those brackets! It made me think about whether it was a good idea at all, but I figured I'd try it. Still skeptical, but the carbs need serious attention, so I won't worry about things that are working!

Thanks for the confirmation...

telecaster

MRFLATSIX, I also have 1970 911 with an MSD 6al box that has just been recently installed. My car is an 911E. I also have a crane optical trigger. But....I can't seem to get my tach working. I have tried various options . Such as, no adapter and hooking it up directly to the white trigger wire and directly to the tach out put of the MSD. No luick. I have also tried using the 8920 adapter and the tach still does not want to work. Could you please tell me how you wired your adapter up and any other hints you may have. Thanks

lateapex911

Jay...I seem to remember the possibility of damaging the tach if it is hooked up incorrectly. Not positive, but I wanted to post first to get the right advice before I took the plunge. What order did you try? Hopefully you tried the adapter first...

MRFLATSIX

Hi Jay:
My car is a '70 911E with Weber carbs. My adapter has 4 wires red,black.white, and purple.Red goes to the ignition switch,black goes to ground, white goes to the tach output on the ignition box and purple goes to the tach. Incidently, I no longer have the Crane optical system on my car. I took it off and replaced it with a Pertronix Ignitor. There was nothing wrong with the Crane, it worked fine. I just like the pertronix installation better. I also use the MSD Blaster coil. Good luck

telecaster

Well, good news. The tach adapter worked when I wired it up according to your directions. Thanks for the help.

Just a word of warning about ignition boxes. A local parts shop recommended using a Mallory ignition box. I gave it a try and later found out I had a bad box. I had no signal at all from the tach wire. The best plan is to stay with MSD. They are a much better product over all compared to the Mallory.

The bad news. My starter has died and I am having it replaced tomorrow. Moreover, while I was waiting in a local drive through, a big black 2003 GMC truck backed into my rear quarter panel. While waiting in line, I looked over at my passanger and heard "oh my God" and then the "crunch". That is when I saw the truck. Oh well, time to make a claim and then off to the body shop when the starter is replaced.
It has been a wierd week.

MRFLATSIX

Jay:
You sure are having a run of bad luck this week. At least the tach works now.
Good luck on the other stuff.