aaronz28

is there anyway to calibrate a mech tach in these c2s?

i hadn't given it much thought until this weekend when i was warming up my car to check timing - my light has a digital advance and tach on it - i had it resting on the wipers - connected - and while i was warming the engine up - noticed that the digital readout was about 300rpm off at 2000 - but as i revved up - it got worse - so much that as the mech tach read 4000 rpm - the engine was really only running at 3200

its not the biggest issue in the world - but i'd like it to be accurate -

65GGvert

I'd check it with a 3rd tach before I started doing any serious work.

Mike67nv

To answer your question, yes, there is a process to calibrate your tach. It is done by gaussing/degaussing the magnet cup, just like speedo calibration. The unit has to come out of the cluster to be serviced.

65GGvert

Did you ever verify if the mechanical tach was off, or if it was the electric box you were using?

rfn026

Gauges do wear out. It happens. the big issue on the C1 is getting the tach out. Here's an article I wrote on gauges last year.

Richard Newton

aaronz28

verified with another tach - its definitely off

the miscalibraton gets worse as the engine revs up -

at low rpm, its pretty accurate - once above 2000 rpm its off by about 300-400 - at 3500 on the tach, engine is spinning 3000

aaronz28

this is a 64 - so C2

Donny Brass

accurate tach is just $300.00 away for a full guage or $160 for the kit

http://www.zip-corvette.com/53-71-el...rsion-kit.html

aaronz28

gonna be going for NCRS Flight judging next year

Donny Brass

then the tach cannot be accurate