Can someone explain this to me?

[Nabeel Rahimpour]

Hey all,

So I was watching this (http://www.youtube.com/watch?v=4Ai0uSj_OVE&t=14m09s 14m 9s in) video on Youtube, and I noticed that the RPM gauge was very jumpy, almost like it was a low frame rate video.

This is an older car from the 50s, so is this just how they were back in the day, or is something wrong with this car?

In either case, why is this happening? Is it a mechanical RPM gauge, or an electronic one tied into a hall sensor?

So many questions, such little information!

Thanks for your help guys!

Topic

[Andrew Button]

Thats got a cable from the distributor to the gauge. Its sticky and at a low rpm it takes a bit for it to be smooth, probably old grease in there.

[Mike]

While it could be a sticking cable mechanism, what I’m seeing doesn’t really look like it.

There are some tachometers that momentarily hold the needle at the highest RPM the tach sees every few seconds. This might be that kind of system. A sticking tach cable has a much more erratic floaty/bouncy look, this tach has a more precise clockwork kind of feeling, like a stop-start second hand on a chronometer.

And, it’s entirely possible that this could be an electric tach, either as original equipment or as a replacement/mod sometime during this car’s 60 year life.

[Author]

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