Tic-Toc-Tach is off with MP Orange Box EI

[BananaDan]

Hey guys, I have an MP Orange Box EI system on my 440 Charger.  I recently got my dash cluster back from Instrument Specialties and due to a miscommunication they didn't do the EI upgrade to my tic-toc-tach after all.  The tach is definitely showing incorrect RPM numbers and under a load (2500-3000+ RPMs) she jumps all over the place including into the redline area.  I spoke with Mike and he says that I shouldn't need the EI upgrade, he says that he has never seen a tic-toc-tach provide false RPM readings with an Orange Box setup, only with something like an MSD.  He suggested I try a tach adapter from MSD to see if it helps, or I can send my tach back to him and he'll do the EI upgrade to it but he doesn't think I should need it.  He had my tach test results from the three bench tests they put it through and he said it tested out fine all three times.  My questions:

Has anyone had issues with an MP Orange Box and a stock tic-toc-tach?  The Orange Box is an upgrade to my 70 done by a previous owner, 70's were points from the factory.

If I were to try a tach adapter, which one should I get?  Mike recommended the MSD 8910, but I read somewhere else that I may need an 8920?

Could I have a problem with my coil that is causing this issue?  I have one of the restoration/reproduction Mopar coils (02495531) from MopartsRacing.com  http://www.mopartsracing.com/parts/electronic.html.

Dan

[BigBlockSam]

 

[resq302]

I know at idle my tach is reading incorrectly and it was restored by Auto Instruments.com about 8 years or so ago.  Ive just given up hope on it and whenever I need to tune my car I have a digital timing light that has rpms on it also.

[BigBlockSam]

i have an msd adapter in my rod and it did the job . i have a msd distributor and 6al box in the rod. without the adapter the Tach was way off. i have dolphin gauges in that car . 

[70charginglizard]

and under a load (2500-3000+ RPMs) she jumps all over the place including into the redline area.  

Regarding this part of the issue. I had a similar problem like this and ran a seperate ground wire from the lower outbd screw that holds the tic toc tach in place and screwed that in real tight and grounded to the dash frame just below that real good and the jumping around problem on mine went away after that.

I'd give that a try on yours Dan and see if that helps any.

oh and bty....I also have the MP orange ignition box on mine and no upgrade to the cluster for me.
No problems since I added the additional grounding strap to the tach as I mension above to mine.  

[BananaDan]

Interesting, so it could be a grounding issue?

[Just 6T9 CHGR]

That is possible.....I run the MP electronic ign as well (actually a hotter setup from FBO racing) and the tach reads OK

When I say OK it doesnt spike up to the redline ect....its NOT accurate at all....mostly for show..  I use my hidden shift light/tach for accuracy

[doctor4766]

So what actually is the issue with EI boxes and tachs?
I too have the orange box but use an aftermarket tach.
It seems to run ok up til 3000rpm but doesn't seem to want to go any higher than that, even though I feel the car is revving more than 3000.

[70charginglizard]

Interesting, so it could be a grounding issue?

Id put money on it if I were a betting man

[resq302]

That is possible.....I run the MP electronic ign as well (actually a hotter setup from FBO racing) and the tach reads OK

When I say OK it doesnt spike up to the redline ect....its NOT accurate at all....mostly for show..  I use my hidden shift light/tach for accuracy

But Chris, you have an automatic.  Why ever would you need a shift light?   

[Just 6T9 CHGR]

But Chris, you have an automatic.  Why ever would you need a shift light?  

You figure it out Brian....

[A383Wing]

You figure it out Brian....

that is cool.....you have it made or did ya make it yerself?? 

[Rolling_Thunder]

 I'd take a point off if I were judging that car                


Then again people would have a field day with my car     

[70charginglizard]

Interesting, so it could be a grounding issue?

Well Dan?

[BananaDan]

I don't have time to work on her until this weekend.  I'll keep you all posted.

[resq302]

But Chris, you have an automatic.  Why ever would you need a shift light?  

You figure it out Brian....

Ahhhhhh...... looks like someone has a reverse valve body   

[Just 6T9 CHGR]

A full manual one at that.....for the past 13 years!

[440]

A full manual one at that.....for the past 13 years!

I thought you were bit by the "originality bug" ?

[resq302]

A full manual one at that.....for the past 13 years!

I thought you were bit by the "originality bug" ?

It is.  Its "original" to him!   

[elacruze]

Interesting, so it could be a grounding issue?

Id put money on it if I were a betting man

With electronics, it's *always* a grounding issue...

[Back N Black]

That is possible.....I run the MP electronic ign as well (actually a hotter setup from FBO racing) and the tach reads OK

When I say OK it doesnt spike up to the redline ect....its NOT accurate at all....mostly for show..  I use my hidden shift light/tach for accuracy

Got a pic of you hidden tac? i need ideas.

[Just 6T9 CHGR]

Got a pic of you hidden tac? i need ideas.

Started a new thread not to hi-jack this one too badly

http://www.dodgecharger.com/forum/index.php/topic,81258.new.html#new

[dodgedarren]

I just bout a NEW OEM Tic Toc Tach and is came with no wiring diagram. Does anyone have a photo or diagram of what goes where on the back of the tach???

[Dans 68]

I just bout a NEW OEM Tic Toc Tach and is came with no wiring diagram. Does anyone have a photo or diagram of what goes where on the back of the tach???

http://www.dodgecharger.com/forum/index.php/topic,71037.0.html

Dan

[dodgedarren]

Mine has 5 terminals