Tacho rattle

[Mad4slalom]

Hi all , out in the 72 for more get to know her runs. Anyone have a tacho or tacho cable rattle? I take it the cable is mechanically driven via the distributer shaft? Do these cables nee oiling or is it possibly the tacho itself.I tried insulating anywhere it was touching anything but no better. Any thoughts? Many thanks.

 

[Roscobbc]

Tacho cable needs occasional lubrication - probably annually/bi-annually - can't recall whether grease or oil. Be careful of cable routing from engine compartment - bends need to 'gentle 'if possible.......or ------- 'snap'

 

[Mad4slalom]

Tacho cable needs occasional lubrication - probably annually/bi-annually - can't recall whether grease or oil. Be careful of cable routing from engine compartment - bends need to 'gentle 'if possible.......or ------- 'snap'

Thanks , I will look up procedure.

 

[CaptainK]

I'd be interested in that too. I replaced the cable on mine a while back as the tacho was a bit hit and miss - under acceleration it would rev up, then drop, then rev up again. Fine afterwards, especially with my new HEI distributor as well (still cable driven).

 

[antijam]

As Rosco pointed out it's worth checking that the routing of the cable from the distributor through the bulkhead is optimised. The traditional positioning of the Distributor on a SBC is with Number one lead towards the front of the engine but on the Corvette this puts too sharp a curve in the tacho cable and Chevrolet issued a service bulletin to reposition the distributor to facilitate the cable run. If the distributor has been replaced it may not have been set to the right orientation to achieve this.

 

[Roscobbc]

There was an aftermarket 90 degree tacho cable 'adaptor' on the USA market at one point (don't know if its still 'out there') - idea being that instead of a really acute bend at the rear of the instrument panel (or engine) and you could use the 'adaptor'. Simply screwed in to speedo head, distributor (or rear of tacho) and cable would screw in to this in turn. https://www.corvettemods.com/thumbnail.asp?file=assets/images/fr1167.jpg&maxx=350&maxy=0

 

[Chris Sale]

I have found a 'Lubricating the Cable' document that I copied from the Willcox Corvette site some years ago. Have just looked for it on Willcox but it seems the document is no longer available. Anyway, this is a summary what it says:

- All cables assembled from bulk stock must be lubricated before installation
- in extremely hot and dusty conditions, relubrication may be necessary at intervals of approx. 20,000 miles or 2 years
- AC has developed a Type ST-640 speedometer lubricant. This assures free running in extreme temperatures and prevents rust and corrosion
- Only AC ST-640 lubricant should be used. Other lubricants will work their way up the cable and into the speedo/tach head
- The cable should be lubricated ONLY along the lower 2/3 of its length
- Place 'one inch' of lubricant in palm of hand
- Feed the cable through the lubricant in you hand until the ;lower 2/3 is lubricated
- Cable operation will lubricate the upper 1/3
- Excessive lubrication will force grease into the speedo/tach heads and will stop the speed cups from operating properly

For reference, I last lubed my speedo & tach cables in 2008, using Moly chassis grease as I could not locate any AC Type ST-640. I used the procedure as outlined above. That was about 46,000 miles ago now and my speedo and tach are both still working OK.

Chris Sale
'64 Coupe

 

[Roscobbc]

Last time I 'lubed' my speedo cable (with grease I'm sure) was following replacement due to it breaking (no doubt due to not being lubed) like Chris I haven't needed to re-lube it (or rev counter cable since) since then..........(probably in 2002.....).

 

[Chuffer]

I read somewhere a while ago that white lithium grease was the thing to use . WD40 make it amongst others . Bought a can for my speedo cable but it`s one of those ` Round To It ` jobs .

 

[CaptainK]

There was an aftermarket 90 degree tacho cable 'adaptor' on the USA market at one point (don't know if its still 'out there') - idea being that instead of a really acute bend at the rear of the instrument panel (or engine) and you could use the 'adaptor'. Simply screwed in to speedo head, distributor (or rear of tacho) and cable would screw in to this in turn. https://www.corvettemods.com/thumbnail.asp?file=assets/images/fr1167.jpg&maxx=350&maxy=0

I have one of these somewhere in my parts box. Was gonna put it on my Vette as the cable drive angle was weird. Then the distributor started dying anyway so I replaced it and it was positioned at a better angle and no need for the 90 degree adapter.