21-11-2018, 10:04 AM
Hi.
I'd be very wary of fitting an inductively coupled tacho in a rear engined car. On these rev counters you are breaking into the points to coil connection, then two cables are running from the contact breaker points connection on the distributor and the other from the coil, these are long cable runs and lossy, that added to the loss in the rev counter could mean a drop in HT volts and poor cold starting or misfires, then of course if a car radio is fitted the long leads act like an impulse transmitter!
I'd be inclined to look out for an impulse fed tacho which wont give the losses.
If interested I've done some repairs on an Aston Martin DB6 Tacho and the process is on my youtube channel, it was converted from positive earth to negative by replacing the germanium transistors with npn equivalents and reversing all the polarity conscious components. I saw about 0.75 volts of a drop on the inductive coupling at 2 amps current.
I'd be very wary of fitting an inductively coupled tacho in a rear engined car. On these rev counters you are breaking into the points to coil connection, then two cables are running from the contact breaker points connection on the distributor and the other from the coil, these are long cable runs and lossy, that added to the loss in the rev counter could mean a drop in HT volts and poor cold starting or misfires, then of course if a car radio is fitted the long leads act like an impulse transmitter!
I'd be inclined to look out for an impulse fed tacho which wont give the losses.
If interested I've done some repairs on an Aston Martin DB6 Tacho and the process is on my youtube channel, it was converted from positive earth to negative by replacing the germanium transistors with npn equivalents and reversing all the polarity conscious components. I saw about 0.75 volts of a drop on the inductive coupling at 2 amps current.
