I found the answer via search...duh.....thanks Klortho..it was your info that answered my question.

I am installing an lt1 in my IROC and am not sure about the tachometer. I plan to purchase 90-92 instrument cluster. Do I need to be concered about if the instrument cluster came from a six or eight cylinder car? If so is there a way to tell the difference from looking at the tach redline or maximum indicated speed?

 

Even though I have an 89 cluster this may apply to you. I took the tach apart, changed capacitors and now it works fine. Before it just read double rpms, swapped capacitors, problem solved.

 

What value cap. did you install? Thank you for the information.

 

Here's the link to the post.
https://www.thirdgen.org/forums/elec...ach-fixed.html

 

Thanks again, that makes the cluster worth the 20 bucks.