tach and start problem
 

i guys, i have probllem with my tach, i read many post on this problem and it reveal to be the alternator, but my problem seem to be a bit different. my porsche did not start, the engine is cranking but the engine won't start. it seem to be a tach related problem because, when i turn on the key the tach is at 0rpm and when i crank the engine the tach go at 8000 rpm but the engine dont start. sometimes the engine start with the rpm bouncing and suddendly the tach go to 8000 rpm and the engine die. any help is welcome. i have a permatune on the engine i don't know if it can be the source of my problem

i think i find my problem, it appear that my permatune is defect, when my tach stick at 8000 rpm, the box is whining very loud, i hit the box with a screwdriver and the noise stop and the rpm fall to 0 rpm, the car start and die again when the tach hit 8000rpm. so i have to change this box, witch box should i buy, msd, bosh or a new permatune, my porsche is a 911t 1970 with a 3.0sc of 1983. thanks you everybody

I would vote for MSD. They seem to be highly regarded. I have two 6ALs in a twin-plugged '83 SC.

and the tach work fine?

Well, my tach has nothing to do with the MSD units, though some tachs need to be driven by them, and there's a provision for that. Don't know what the situation would be in your car, though you apparently have basically the same engine that I do.