I bought one from the parts place. It sits at 3500 rpm not running. Then when started it idles around 4500. Is there a way to adjust. I'm waiting to hear from parts place. It is an hei distributer with a tach terminal.

 

Hei does not put out a clean tach signal. I was able to make a fix mine with a resister and ground wire and it is all under the hood.
Search the internet for the resistance needed.