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Re: Vega Tachometer - "I killed 2 over 35 years ago"

PostPosted: Wed Jan 10, 2018 5:35 pm
by spencerforhire
I do not know firsthand if the early points ignition Vega tach is any different from the later HEI version. I never owned an early GT. The Cosworth would presumably have HEI, but the calibration would be wrong for your V6.

Re: Vega Tachometer - "I killed 2 over 35 years ago"

PostPosted: Fri Jan 12, 2018 10:41 am
by 74_Vega_GT
Thanks again for the input. So, I'll get in touch with Tim McCabe somehow and send off the 8K Cosw. tach. for testing and re-calibration and go forward from there. I did discover that I have 2-120 MPH speedos. One is from a 74 without the blue KMH dial. The numbers and face plate are a little faded but I might just live with it.

Re: Vega Tachometer - "I killed 2 over 35 years ago"

PostPosted: Mon Jan 15, 2018 10:59 am
by 74_Vega_GT
Thanks for the info on the MSD adapter, but it creates new questions. The PDF that I read concerning the 8910 and 20 adapter differentiates between the ignition pulse and the ignition voltage. What I need to know is, did all 75 Cosworth Vegas have electronic ignition? Did all Cosworth Vegas come with the electronic fuel injection or were some available NEW with the dual Weber setup and would thaty make a difference as to whether or not it had an H.E.I. system or a points system.?? I am hoping not to kill the Cosworth 8K rpm tach that I have. How does one know when an adapter is needed and which of the adapters is needed in this instance? We are using the inside and outside harness from the 74GT.
Also, the wiring diagrams I downloaded here on the 74 and 75 Vega show no tachometer wiring, Is there a Mitchell wiring diagram for the GT dash that I may have missed?
Thanks in advance.

Re: Vega Tachometer - "I killed 2 over 35 years ago"

PostPosted: Mon Jan 15, 2018 8:20 pm
by spencerforhire
I presume all Cosworths had some form of breakerless ignition, so therefore a tach from one should work fine. GM tachs are voltage triggered. The current triggered setup is found on 1960's Fords. If you want some insurance against damaging that rare 8000rpm tach, I suggest the 8920.

Re: Vega Tachometer - "I killed 2 over 35 years ago"

PostPosted: Tue Jan 16, 2018 11:17 am
by dindin
Cosworth's all use the HEI ignition and they all came with Fuel injection from the factory,

AL