Griff 500 bouncing rev counter

Yes it is quite common and a well known "feature" on TVR's of this era another case of TADTS(They all do that sir)

The supposed fix is to run the tacho signal wire through the coil of a standard relay to smooth out the spikes which cause the bouncing.

Ahh thanks

The car has magnecor kv85 competition leads.

Why do they make the Rev counter bounce ?

They are about the worse leads you can fit to a road engine, as the lead resistance is very low, that leads to big voltage spikes in the coil primary as it switches. This causes the glitching of the rev counter. You can try more resistance in the spark path, like resistive plug shrouds or resistive plugs. The cheapest option however is to put a standard carbon cored king lead in from the coil to the distributor, which may be enough to calm things down.

The power the spark delivers is irrelevant once the combustion process has started, so you only need enough power to start the burn reliably and no more, as the excess energy simply burns the plug tips out and spikes the coil. Any idea that fitting low resistance race leads to a road engine to produce more power is just wishful thinking im afraid- not that stops anyone out to make a fast buck of of these highly over priced leads selling them.

I would have said the Bosch OEM ones, but I gather they dont do them for the Rv8 any more. I think the genuine Lucas work well enough, but Id change them on a fairly regular basis in a hot TVR engine bay.

On inspecting the leads a noticed this, so I assume worth changing ?

looks like sparks found a way through that?

Speak with Magnecor, they will probably change that damaged one FOC.

Bit more info and possibly useful linky here...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...