carbureted 350 rattles at idle intermitently - 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 01-26-2008, 06:11 AM
Registered User
 
Last photo:
Join Date: Jan 2008
Location: Chile
Posts: 376
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
carbureted 350 rattles at idle intermitently

Hi guys,this is strange
we have been workin on a 1975 350 camaro with a brand new Edelbrock carb and it idles perfect ! but after its warm,it rattles a bit,and come back to normal idle could it be fuel pump? what do you think its causing this ? Its not the only carb car i've seen doing that. what causes that little rattling ?
thanx !

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-26-2008, 08:45 AM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls, Washington
Posts: 5,215
Wiki Edits: 9

Thanks: 99
Thanked 130 Times in 121 Posts
Can you be more specific and define 'rattle' and tell us where it seems to be coming from? Does the engine pull down, stumble? Is there a pattern or just intermitten? Have you observed your timing at idle to see if it's fluctuating?
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-26-2008, 09:00 AM
Registered User
 
Last photo:
Join Date: Jan 2008
Location: Chile
Posts: 376
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Thanx 68,i will check,take note and post
thnx
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-26-2008, 03:03 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,524
Wiki Edits: 0

Thanks: 2
Thanked 330 Times in 327 Posts
Possible cracked, or loose flywheel (auto flex plate) bolts (cracks between the bolts) or its ring gear welds are broken. Loose torque converter bolts or internal torque converter problem.
Possible rattling transmission cooler lines. Possible loose camshaft bolts hitting the timing cover. Possible clutch fan problem. Sometimes a fan belt can make this noise too.
Is this a new motor? or...
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-26-2008, 03:12 PM
Registered User
 
Last photo:
Join Date: Jan 2008
Location: Chile
Posts: 376
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
its a rebuild 1975 engine
with heads from a chevy 400
maybe is the 400 heads ?
im talking about the car parked,at idle
thanx
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 01-26-2008, 03:41 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,524
Wiki Edits: 0

Thanks: 2
Thanked 330 Times in 327 Posts
Don't think its the heads. The only difference between the 400 and 350 smog heads are the extra steam holes in the 400 heads decks.
What about idleing in gear?
Try to nail it down a bit. Remove the fan belt and run the motor for a short time to see if its fan/accessory related or internal or transmission related.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-31-2008, 03:49 PM
Registered User
 
Last photo:
Join Date: Jan 2008
Location: Chile
Posts: 376
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Ok i got news !!!!!
we were watching and putting ear on the camaro a couple of hours ago.-
its not really a rattle,the engine runs pretty smooth
but this will describe the problem perfectly

I go back to the exhaust tips to hear the engine and its amazingly steady if not for some "fffdd ffffd " sound comingfrom the exhaust pipes in a cicle
this is barely noticeable,you have to be real anal,but its there !
the "fffd pffft " sound its almost unnoticeable,you have to sit in the exhaust tip to hear it,i noticed the driver side pipe "fftt " noise its more than the right side but coming in a cicle i guess its from teh engine ....what can it be ?
its like it throws air ...maybe a non adjusted valve ?? maybe some rocker arm ? im juest guessing !
help!
thanx
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 01-31-2008, 06:14 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,684
Wiki Edits: 0

Thanks: 3
Thanked 403 Times in 348 Posts
Quote:
Originally Posted by Calderone
Ok i got news !!!!!
we were watching and putting ear on the camaro a couple of hours ago.-
its not really a rattle,the engine runs pretty smooth
but this will describe the problem perfectly

I go back to the exhaust tips to hear the engine and its amazingly steady if not for some "fffdd ffffd " sound comingfrom the exhaust pipes in a cicle
this is barely noticeable,you have to be real anal,but its there !
the "fffd pffft " sound its almost unnoticeable,you have to sit in the exhaust tip to hear it,i noticed the driver side pipe "fftt " noise its more than the right side but coming in a cicle i guess its from teh engine ....what can it be ?
its like it throws air ...maybe a non adjusted valve ?? maybe some rocker arm ? im juest guessing !
help!
thanx
A little odd running on idle isn't that unusual. First there's always the possibility that the exhaust system leaks air some place, which is why when you plug it with the proverbial potato, it doesn't blow out. Mufflers, brackets, cat converters and simple pipe movements all contribute. Add to that the exhaust flow is not unidirectional from the engine to the chrome tip. The thing is breathing in and out especially at low idle speeds.

Then there is the weak idle mixture. High idle vacuum keeps the molecules far and few between inside the combustion chamber. Spark doesn't necessarily even result in a burn and certainly not a complete burn. So it's not uncommon to have either a misfire or late fire that makes sounds in the pipes.

So I'm not sure this is anything to get too excited about.

Bogie
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
Port or Full time vacuum cool rockin daddy Engine 129 10-05-2010 03:00 PM
Carb tuning issues - 750 speed demon lightningcow Engine 57 07-01-2009 07:32 AM
Chevy 350 Won't Idle Down DavidMClary Engine 9 09-24-2003 11:31 AM
sbc 350 miss under idle Walker Engine 2 07-29-2003 09:02 PM
New 350 Chevy runns rough and won't idle 66nova Engine 3 08-01-2002 01:22 PM


All times are GMT -6. The time now is 05:38 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.