6 cylinder in my 86 hatch, the tach works, but i wonder if its reading correctly.... its the original one from the 4 cylinder.

Probably not. 2 too many cylinders. Hook up an aftermarket one to verify. They adjust for the 4, 6, and 8 cylinder motors. Or hook i tup to a diagnostic scope and check the rpm's that way.

ya, im assuming im reading 50%higher than the revs im realy running.

 

do aftermarket tachs have settings for dual or single fire ignitions... ours is dual fire, but im just wonderin...

I don't know, I would assume so as we aren't the only ones with that type of system. Call around and check with different parts outlets.

1. go by what real idle speed is, and what "indicated" idle speed is

2. use a non contact optical tach

3. use a contact mechanical tach :cool: