It was in the car when I got it. From the marking on it appears to be an original GM tach. It was hooked up to the HEI ignition.

Tried pulling on the pointer it wont budge.

 

PS. I'm thinking a clock lens is interchangable.

Good idea re the cleaner. (I'm thinking it might be cracked though?)

pudge444 wrote:

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I already had it apart just don't how to go further taking it apart. Scared to trash it.

I tried using a plastic cleaner/polisher on my other lens, I totally trashed it. I wont be doing that again.

-- Edited by pudge444 on Monday 11th of September 2017 10:15:13 PM

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 DL hand cleaner(no grit). Have used on face shields/glasses/lenses etc for years. 

PS. That little white blob on the back of the needle that looks like wax... that ain't wax. Don't try hearing it to remove it as the larger black piece will melt first.

66 327 sd wrote:

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Not sure what you are trying to accomplish? If you're looking to replace the lens, you're there. My understanding is that the factory tach won't work on the HEI, but the reproductions do.

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I want to replace the lens with this, https://www.npdlink.com/store/products/lens_instrument_panel_clock_us_made_oe-179007-10673.html

Does the chrome knob pull off?

Not sure what version of HEI was on the car, I replaced it with a DUI HEI, http://performancedistributors.com/product/chevrolet-streetstrip-dui/. Time will tell if it works.

 

...and if it doesn't work with your upgraded ignition, I'd be interested in buying it as I fried mine :(

That blob is simply cast pot metal (part of the knob on the front) they press it together with the needle in place with a vice type tool (that's why you see the imprint on it) if you carefully remove material from that, the knob will come out. Pay attention to how it is put together. Most have a spring washer and a paper washer. Once you have it apart, you can do a few things to put it together, You can carefully hammer to fold the remaining material over to hold everything back together. You can use a combo of the previous with some epoxy, or you can do as 66 states and use a set screw, but you will have to drill the back post of the knob.

Don't know if this will help you Kevin with your tach knob, because this relates to my experience  with similar looking knobs on clocks.

On my 1963 Pontiac the knob on the clock is threaded and to remove you need to hold the stem and turn the knob 

counter clockwise to remove it.

Another style is (as mentioned earlier in the thread) is a small flat head screw in the center of the knob that has to be removed to take the knob off.

I'm thinking if you have a what looks like glue at the top of your knob,someone has lost the small set screw and has filled it with glue to secure the knob.

I don't recall ever seeing glue being used with these small knobs......but they may have.

Anyway here are some pictures of  the knobs I'm familiar with.....I'm sure there must be a member with the same tach you have that could advise

you better to how the tach knob comes off. hope this may help you somewhat.

-G