mk2 16v clocks in 20v conversion

[hc20v]

I have had some 16 v clocks fitted in to mk2 20v
its 90spec 1.3 shell

the rev counter does not always behave its self and and bounces the needle around alot not giving a true reading all the time on the revs

does anyone have any ideas on how to fix this or have i just bought another set of bad clocks

[danny_p]

depends whitch of the meany ways youve chosen to drive your tacho oh and what ecu your running