Chevy 235-6 cyl Oil Presure Fluctuations - 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 06-09-2006, 10:17 PM
Registered User
 
Last photo:
Join Date: Nov 2005
Location: North Carolina
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Chevy 235-6 cyl Oil Presure Fluctuations

Hi Guys, Any help here will be appreciated! Last month I installed a rebuilt head onto my '55 model 235-6 cyl (in my '48 Chevy Pick Up) to get hardened seats, new valves, springs, etc., It runs great with more power and no more lead additives to put into my gas-Yeah! But last week I noticed my oil pressure gauge, which normally runs full up at 30 psi when under power and dropped to 15 psi when at idle at operating temp ( with no pulsing)-NOW it will drop from 30 down to about 20, go back up in about 4-5 seconds. At full stop, it will drop to almost 0 and then move up to about 15 and pulse down to 10psi and back up to 15. I am use to no change except when I idle but the needle keeps dancing and it drives me nuts! I hate it when something is not right-so any ideas on what or where to check-throw them my way! Thanks!!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-09-2006, 10:47 PM
farna's Avatar
Member
 
Last wiki edit: AMC V-8s Last photo:
Join Date: Sep 2002
Location: Batesburg-Leesville, SC
Age: 52
Posts: 1,636
Wiki Edits: 14

Thanks: 0
Thanked 15 Times in 14 Posts
Did you remove the oil pressure line at any time? Sounds like an air bubble in the line. It's nearly impossible to get all the air out of the line, but you can bleed it by loosening the fitting behind the gauge just after shutting the engine off. You can do it with engine idling, but will get more oil out that way... and all over everything. Use a rag to catch the oil. Air could have been trapped in the block oil passages when you took the head off and made it's way to the line. If it's an electric gauge, suspect the sending unit.

If that's not the problem, you need to double check the gauge. A portable air tank with about 20-30 psi in it will work, or try another gauge. I'd give it 200 miles or so to work any air out before I started suspecting oil pump issues. Then I'd change the oil and use an engine flush (or replace a quart of oil with trans fluid or diesel oil, just don't operate the car with the mixture -- fast idle is enough -- diesel is the main ingredient in Gunk Engine Flush, by the way) and change the oil before suspecting the pump or bypass valve.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-09-2006, 11:35 PM
Registered User
 
Last photo:
Join Date: Nov 2005
Location: North Carolina
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks!

Thanks for the info. I did take the oil line loose. It is the original mechanical guage so it may well be an air bubble. I will try the bleeding first and see what happens. I had thought about the flush also as I had to scrape gaskets and stuff so I may have some trash in the pickup screen, but I drained the pan and put new filter on after the head change, so I hoped that would take care of any trash. Thanks for the info!! Dan
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-10-2006, 09:54 AM
willys36@aol.com's Avatar
Hotrodders.com Moderator
 
Last wiki edit: How to rebuild a Rochester Quadrajet 4MV carbureto...
Last journal entry: How to change auto shift timing on 200R4
Last photo:
Join Date: May 2002
Location: Bakersfield
Posts: 8,388
Wiki Edits: 21

Thanks: 1
Thanked 4 Times in 4 Posts
Did you reuse your old rocker arm shaft? Those things get pretty worn over the years on 235s (mine was worn almost 1/16" when I tore down my engine for a rebuild!) and can be a major source of pressure leakage.
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 Oil presure on a 350 sb??? Robbie Hotrodding Basics 10 09-27-2012 02:04 PM
Oil leak in 350 Chevy Ed Baltera Engine 18 07-29-2012 11:24 AM
Small Block Chevy Oil Pressure knizet Engine 25 03-21-2008 04:21 PM
chevy small block possible low oil pressure? ruski Engine 24 04-24-2006 09:18 PM
oil presure digitalfrek Engine 2 01-23-2004 09:33 PM


All times are GMT -6. The time now is 10:19 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.