How does one convert the standard 4 cylinder tachometer for use with an engine with a greater number of cylinders? I have a V8 conversion. I have read the various postings and it is not clear on how to do it for a 75 914. I assume those who have 6 and V8 conversions have made the necessary tachometer modifications.

Also, the tachometer bounces around. I understand that there is also a fix for this condition, and again, I am not clear on what is involved.

Anyone know how to make the conversion and fix the bounce?

Normally, for a six conversion, a 911 tach is substituted for the factory 4 cylinder tach. It has the correct redline for the six.


As for the V-8, either build a divider circuit to half the number of ignition pulses, or just send the tach to North Hollywood or Palo Alto speedo for repair and recalibration.


They can fix your bouncing problem too.

The conversion is usually performed at a shop like PA Speedo or NH Speedo.

The bouncing is usually external to the tach. Check the wires at the coil and the back of the tach very carefully. A dirty or even slightly loose connector will cause this. It may LOOK fine, but can still be loose. Take the tach wire at the coil and check for any breaks in the insulation. If you're feeling brave, bend the wire and see if the insulation breaks. They often do from 30 years of engine heat. The fix is to replace the entire engine harness (see Jeff Bowlsby for this), as all of the insulation will be in the same state.

Buy a cheap pep boys/JC Whitney tach and transplant the movement to the Porsche case. Just make sure it has the correct sweep. Did my 914-6 crankfire and my A-H 3000 V8 this way.

North Hollywood Sppedometer does excellent work. They rebuilt my tach for the Subaru engine. Works perfectly and looks outstanding. The only gripe I have is now I have to have my other gauges refinished to match the brand new looking tach!

QUOTE (WRX914 @ Feb 1 2006, 10:50 AM)

North Hollywood Sppedometer does excellent work.