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Old 10-05-2019, 06:37 PM
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Interesting vacuume gauge issue

So I got a new 2'' vacuum gauge for the interior of the car and the needle is showing good vacuum (between 17-18 in) however the needle is shaking very rapidly between about 2 measures to the point that the tip of the needle just looks like a blur. I also have a vacuum canister in the engine bay which has a vacuum gauge attached to it which shows the same reading as the one inside the car but it has a steady needle. In addition, just to confirm I hooked up my regular vacuum gauge to the carburetor and that gauge was also showing a pretty steady needle. I'd say there's an issue with the gauge but I've seen some videos online about the same gauge with a steady needle.




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Old 10-05-2019, 07:19 PM
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Diagnostic vacuum gauges usually have a small restriction in line to dampen that. A holley jet perhaps.
It also may be because of the source, close to head on runner maybe.

Try moving source closer to carb base, in plenum of intake.
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Old 10-06-2019, 04:25 AM
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Based on my limited experience, there is quite a bit of variation in quality between vacuum gauges. For example, my dash-mounted gauge had better damping than my diagnostic gauge. I assumed the dash-mounted gauges were always better damped so they would have a steady reading, but it sounds like you have just the opposite.

Bruce
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Old 10-06-2019, 11:20 AM
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I installed a Stuart Warner to replace a cheapo Harbor Freight on the dash panel so all the gauges are SW. The SW at idle with an LT4HOT cam reads 21 inches, the HF read 16. Hmm, that doesn't sound right for the SW. Got out my motorcycle, mercury manometer as the unimpeachable test source. It reads 16 inches at idle. My old test Snap On, dial, vacuum gauge also reads 16 inches.

I sent SW Customer Support several emails some months ago, never heard back. When I get some time to work with delicate patience I'll remove the moderistic cone bezel from the HF gauge and the older bead bezel of the SW and substitue the SW bezel onto the HF gauge so everything on the panel presents the same bezel. Or once inside the SW, I'll see if it's possible to adjust it.

I have an old Auto Meter, Street tach in the 'gonna fix someday box'; light bulb burnt but I haven't been able to get the bezel off to get in to replace the bulb. Given how expensive these things are one would thing in that price range the light bulb would be serviceable without having to disassemble the bezel from the case to get at it. Called AutoMeter they said if I can't get in it send it back and they will replace the bulb. So it went in the, I'll get to someday box, that my son will inherit when I'm boots up in the ground.

Bogie

Last edited by BogiesAnnex1; 10-06-2019 at 11:31 AM.
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Old 10-06-2019, 11:30 AM
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Quote:
Originally Posted by BogiesAnnex1 View Post
I sent SW Customer Support several emails some months ago, never heard back.
Typical.........
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