tach gone stupid

ok im driving a 91 crx with a zc dohc swap, and now both my aftermarket phantom tach and my stock tach have gone stupid... whenever i give it gas past about 4500 rpms both tachs just start jumping around. my phantom tach bounces from 10,000 to 3,000 rpms and my stock tach bounces around 4,000. so i have no idea when im about to tach out or what. does anybody might know what is happening or how i can fix it??? thanx.

Was it doing it before with onlt the stock tach? Mine started doin something like that too, just before the coil went out. Started doin it around 5k then a few weeks later it started jumpin sround 3k, then bam! car dies on the road. I'd check the connections on the ignitor as well, sometimes those come loose .

cool thanx for that input man, ill go check it out to see if that is it... thanx

It is wierd isnt it, mine is doing it at right above 3000 rpm. I sure hope it doesnt go out on the road....again.