I am about to send my tach away to cure an attack of the bouncing needles on my 1970 914-6
I notice it has a 914 part number & dated Apr 1970
are there any material differences between the similar 911 part numbered tach of the day ?
also anything else to ask for to be done while I'm in there ?

TIA
Dennis

It is a /6 tach, it wouldn't work if you had it in a /4, the 914 part number the likely only difference from a 911 tach is the face/redline.
Better back lighting, but you would need to send the speedo and combo gauge to make it match.

The 1970 914-6 tach is calibrated for 6 cylinders. It has to have the "tach adapter" on the relay board in the engine compartment to work with the CD ignition on the 914-6. It is a miniature coil to up the voltage of the tach pulse coming from the CD box. In 71, they updated the tach to work with the CD ignition directly, and eliminated the tach adapter.

You could buy a tach from a mid 70s 911, and move all the guts over to the 914-6 case, including the face plate and the needle. Then just open the tach adapter and put a jumper wire inside it. It will look stock, and work fine.

I had a bouncy six tachometer. North Hollywood speedometer replaced all the capacitors. No more bounce. They also repainted everything. Looks and works like a NOS tachometer. Worth every penny..

So are faulty capacitors the typical cause for a bouncy tach? Mine has quite a bit of bounce and I was thinking about trying to repair it one of these days.

. . .the "tach adapter" on the relay board in the engine compartment . . .

thx Clay

are these adaptors readily available if mine needs one ?

Dennis

I replaced my whole driver board. I now offer the service in Canada.

Bob Ashlock sells a Tack-Adapt, most use it to turn a /4 tach into a /6, but it also solves the bouncy tach issue.
About the cheapest and easiest option.

http://ashlocktech.com/

Please note, last time I had a tach face re-printed NHS covered over the factory numbers at the 12 o'clock position. No way to prove it was a factory item.

Bob is one heck of a good guy and his kids are very nicely done and documented.

I sent mine in to replace the glass. They said the capacitors were leaking, so I had them replace them and when I got it back I noticed the tach no longer bounced.

Oh Hell no!

Those are rare, and working ones are rarer than hens teeth. The same part is used on the early 911, and the 911 guys grab them up the instant they find one, working or not. You can buy an aftermarket tach adapter from MSD that will replace it, but it is a big square box, not a small round can like the factory one.

Here is what it looks like.....



And here is the MSD box that will replace it.

Clay

thanks for your help on this

cheers
Dennis

The Tach Adapt IMO is better for bouncy needle, if you have an MSD and want to try the MSD 8910 red box tach adaptor I'll give you one, just pay for shipping.
But I don't think the 8910 helps bouncy tach, just one that won't trigger the tach when using MSD