Interesting vacuume gauge issue - Hot Rod Forum : Hotrodders Bulletin Board -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 10-05-2019, 06:37 PM
47 Ford Coupe Delux's Avatar
Registered User
Join Date: Oct 2018
Location: Rhode Island
Posts: 178
Wiki Edits: 0

Thanks: 106
Thanked 12 Times in 9 Posts
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.

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 10-05-2019, 07:19 PM
MGK's Avatar
MGK MGK is offline
Registered User
Join Date: Sep 2019
Posts: 197
Wiki Edits: 0

Thanks: 2
Thanked 72 Times in 54 Posts
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.
Reply With Quote Quick reply to this message
The Following User Says Thank You to MGK For This Useful Post:
47 Ford Coupe Delux (10-06-2019)
  #3 (permalink)  
Old 10-06-2019, 04:25 AM
75gmck25's Avatar
Registered User

Last journal entry: Engine replacement
Join Date: Aug 2006
Location: Alexandria, VA
Posts: 2,556
Wiki Edits: 0

Thanks: 4
Thanked 238 Times in 216 Posts
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.

Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-06-2019, 11:20 AM
Registered User
Join Date: Apr 2007
Posts: 13,334
Wiki Edits: 0

Thanks: 392
Thanked 1,472 Times in 1,160 Posts
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.


Last edited by BogiesAnnex1; 10-06-2019 at 11:31 AM.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-06-2019, 11:30 AM
techinspector1's Avatar
Registered User
Last wiki edit: DynoSim combinations
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 78
Posts: 17,528
Wiki Edits: 326

Thanks: 2,103
Thanked 3,072 Times in 2,294 Posts
Originally Posted by BogiesAnnex1 View Post
I sent SW Customer Support several emails some months ago, never heard back.
Reply With Quote Quick reply to this message

Recent Hotrodding Basics posts with photos

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -6. The time now is 05:57 PM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.