C2 Tachometer issue

[Donald H.]

I'm working on a 66. The issue is the tach reads 1/2 the actual RPM. I know, or think I know that the engine turns two revolutions for every one the distributor turns.

So, with a Delco tach drive distributor does the gearing in the tach drive part of the distributor double the speed of the cable to the tach?

The car currently has an aftermarket magnetic pickup distributor with tach drive. I have not been able to identify a brand/make of the distributor. I am hoping the tach drive part of the distributor is the issue and not the tachometer itself.

Thanks,
Don

[Duke W.]

OE distributors spin the tach drive cable at camshaft/distributor speed, which is half of engine speed. That's about all I can say. Since you apparently have a non-OE system that you can't identify, my only suggestion is to get a proper OE system, but since you did not mention anything about the engine I have no idea what the OE system could have been other than either single point or TI.

When asking engine or ancillary system questions, one should always provide basic details on the engine, like the OE (or non-OE) configuration (if known) and known modifications.

Duke