Rick, It sounds like you have a variation of a common problem. I've sent an email to the tech support area of SW to see if they might be able to shed some light on this. From what I've read here it seems the only common pieces between all of us is a SW tach and a pointless distributor. Jim's comment that when hooked to a point type distributor, the SW tach reads OK. This would seem to support (for some reason) these tachs not liking this set-up. If anyone would like to forward their comments to SW, here is the email address:
rthibodeau@maximatech.com
Len