Vacuum gauge needle jumps - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



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

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 06-24-2007, 04:50 PM
Registered User
 
Join Date: Mar 2007
Location: New York
Posts: 51
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Vacuum gauge needle jumps

Hello. Just reinstalled freshly rebuild 350 into 1980 Corvette (top and bottom end rebuild). Auto tranny. Idle is rough -moves up and down. I did a vacuum test using a manifold port: the needle moves very quickly (like a fast windshield wiper!) BETWEEN 13 AND 17. Could this be an internal problem? I did spray carb cleaner around the carb base - nothing. When i cover up the top of the carb with my hands the idle increases and smooths out. Would a bad egr valve do this? I'm stumped and need advice. Thanks in advance!
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-24-2007, 05:02 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 61
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Doc here,

The Vacuum is right on the high side, too low on the low side...

A Rapid Fluctuating needle is indicative Of: bad / Burned Valves, Leakey Valve guides, leaky Valve seals, or OVER~ADJUSTED valves..(along with rough running..)

I'd do a re~Adjust on the valves and try and find any tight ones, then go from there.

If that won't cure it, you may be sending those heads BACK to the machine shop..

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-24-2007, 06:41 PM
ccnova's Avatar
Member
 
Join Date: Nov 2003
Location: Mitchell S.D.
Age: 52
Posts: 62
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Here is a link to a website that shows and explains what the needle movements mean. http://www.users.bigpond.com/ergoff/vac1.htm Hope this link works. I look back at this site alot when tuning our vehicles.
ccnova
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




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


Similar Threads
Thread Thread Starter Forum Replies Last Post
question about ballast resistor and wire gauge redneckprofessor Electrical 25 06-09-2007 01:50 PM
Guages are dead gtipton Electrical 4 05-09-2007 09:14 PM
Vacuum Secondaries Won't Open Fully leejoy Engine 11 08-28-2006 12:30 PM
timing / vacuum tweaked Engine 3 04-08-2006 07:28 PM
Timing ?'s, Idle Speed and Ported vs Manifold Vacuum JoeS Engine 5 11-03-2004 12:34 AM


All times are GMT -6. The time now is 02:50 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.