Ok, so I know you have to use the same Tachometer that the engine originally used, 2.0 with 2.0, 2.2. with 2.2 and so on.

Having a bunch of Tachometers laying around and not knowing which goes where, how do i tell the difference?

Tachs work with a style of ignition, not an engine size. Of course, placarded red lines could vary depending upon the original application.


There are tachs that work with points ignitions (like 914/4s), tachs that work with the CDI box ignition systems and tachs that work off the low-volt signal produced by modern engine management computers.

What do you have?

1.8,1.7.&2.0 all used the same tach.

I think he's talking about /6 tachs.

Best way is to check the part nos. on them against the appropriate PET downloaded from the Porsche website's Classics area (same place as you find the 914 PET).

Otherwise you could call a dealer & hope a kindly parts guy will do a look up for you.

Look for one with a 6300 RPM redline (2.0, 2.2, 2.4, 2.7) ... and on the back it will say 6 Zyl. Of course you can go for an early with a 7K redline (S tach) and fool your friends.

And if all else fails, I'll find my 7K tach and offer you my 6.3K tach that's in the Grey Ghost.

Thanks for the help so far guys!

I have a 77' S engine that is bored out to 2.9. I think I have the right tach, but I want to make sure and not mess anything up.

Will the boring out affect my redline?

In theory, boring an engine will have limited impact on an engine's redline.
That being said, if the larger pistons are heavier than the original, I'd back it off a bit, but usually it is more about mean piston speed and valve train.