1967 tachometer vs cable speed

[Donald O.]

On a 1967 327-350hp, if I spin the tach cable at 2000 rpm drill speed, what should the tach read?
Since I need to send my speedo to Joe Ray, I'd like to see if I need to also my tach.

Don

[Ken A.]

Re: 1967 tachometer vs cable speed

ask joe or 4000 rpm

[Joe R.]

Re: 1967 tachometer vs cable speed

Don,

Just send it along with the speedo and I'll put it on the machine and check it for accuracy! No charge to check for an NCRS member!

JR

[Donald O.]

Re: 1967 tachometer vs cable speed

Don,

Just send it along with the speedo and I'll put it on the machine and check it for accuracy! No charge to check for an NCRS member!

JR

Will do Joe. Just as soon as I can contort myself a bit more, hopefully less than 2 weeks.
DonO

[Duke W.]

Re: 1967 tachometer vs cable speed

If the tooth count on the tach drive and driven gears are the same then the cable turns at camshaft speed, so 2000 cable revs should read 4000 on the tach. Mechanical tachs and speedometers can be calibrated by changing the magnetic flux. I had that done at a local speedometer shop over 20 years ago on my Cosworth Vega's speedometer to compensate for the higher revs per mile replacement tire size.

I also had the electric tach calibrated to be dead on at 7000 revs. I think he reindexed the needle on the pin to accomplish that. It now reads 200 low at idle, but that's okay. I wanted it dead on at the redline.

It's great that we have someone in the community that can do this work. I think that local speedometer shop is long gone.

Duke