'90 Tach Filter - Install Procedures?

[bradvette]

Ever since my engine rebuild, the tach in my '90 has gone haywire. Sometimes the tach works smoothly, most of the time the needle is all over the place. Connection to distributor seems solid, there is no corrosion. My only guess at this point (other than a new or reconditioned cluster) is that my tach filter is on the fritz either from age, or from exhaust header heat (installed Hooker long tubes last winter), or both. Seems coincidental that all of a sudden my tach isn't wroking right immediately after the rebuild.

You can't purchase new tach filters for '90-'91, GM has discontinued for these two years in the C4 line, and no aftermarket for new ones exists. Only sources are boneyards. So......I found a source and ordered a used one.

Can anyone give a procedure for getting to the old one, and replacing it? What should be removed first, etc.

Thanks!