Both rich and lean - 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 09-10-2008, 02:03 PM
Registered User
 
Join Date: Sep 2008
Location: Sweden
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Both rich and lean

Dear all,

My 355 Chevy do not run as I would like it to. I have new alu-heads, twr 9.7 pistons, a 224 and 231 cam, Edelbrock rpm air gap manifold and a 750 vacuum demon. Now to the question. My spark plug 1 and 3 are white and my sparkplug 5 and 7 are black. The oxygen sensor with the edelbrock display shows on both rich and lean. Is there someone that can help me with any input on this?

I have 35 degree initial timing at 3600 rpm, 15 Ihg vacuum at ideal and I have tried with carburetor spray around the carburetor to see if there were any leaks but no rpm change could be heard.

The engine is sitting in a 1970 Camaro with a TH 350

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-10-2008, 07:42 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,753
Wiki Edits: 0

Thanks: 4
Thanked 419 Times in 361 Posts
Quote:
Originally Posted by Jonas.snall
Dear all,

My 355 Chevy do not run as I would like it to. I have new alu-heads, twr 9.7 pistons, a 224 and 231 cam, Edelbrock rpm air gap manifold and a 750 vacuum demon. Now to the question. My spark plug 1 and 3 are white and my sparkplug 5 and 7 are black. The oxygen sensor with the edelbrock display shows on both rich and lean. Is there someone that can help me with any input on this?

I have 35 degree initial timing at 3600 rpm, 15 Ihg vacuum at ideal and I have tried with carburetor spray around the carburetor to see if there were any leaks but no rpm change could be heard.

The engine is sitting in a 1970 Camaro with a TH 350

Do you mean that you have 35 degrees initial timing or 35 degrees total at 3600 rpm? Initial often called "base" it needs to be on the order of 8 to 12 degrees at idle for a street cammed engine. There is vacuum advance which comes in at or slightly above idle usually about 20 - 30 degrees and goes away as manifold vacuum decreases on opening throttle. The other advance if built into the distributor using fly-weights and springs is variously called mechanical, or centrifugal, or inertial advance it usually has about 20- 25 degrees. Total advance is commonly thought of as the sum of the base
and the mechanical and should be from 32 to 45 degrees depending mostly on cam, compression and combustion chamber shape.

If your plugs for 1 and 3 are white while 5 and 7 are black then certainly there is a fuel distribution problem on the odd side of the engine or an ignition mal-function on the black plugs or they are in cylinders pulling oil in the mix. Another possibility is that 1 and 3 are sharing a vacuum leak at the head to manifold joint.

This also begs the question, what do the plugs for 1,2,4,6 look like.

The manifold you have is a dual plane, it is somewhat odd to have cylinders pulling of both the upper and lower planes to show a common problem, that almost rules the manifold out but that's why I'm interested in what the plugs for the even numbered side look like.

Bogie
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-10-2008, 11:33 PM
Registered User
 
Join Date: Sep 2008
Location: Sweden
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thank you Bogie,

Yes I think I am talking about total timing.

The sparkplugs number 2, 4, 6, and 8 looks like 1 and 3. They are white. So I have tried with both go up in jets and adjusting of the ideal screws. But the lean condition will not go away apart from plug 5 and 7 which are black. And they have always been that way since I started up this engine the first time 4 month ago.

Do you think it can be a fuel distribution problem? I will try checking the fuel pressure to night. Or can it be the demon?

And thank you Bogie for your response!
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-11-2008, 12:06 AM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
This may sound 'crazy', but do you have 5 and 7 crossed in the firing order?

Either that, you are having a problem with plug wires, or spark plugs. Possible compression, but I doubt it.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-11-2008, 12:26 AM
malc's Avatar
Living At The Speed Of Life
 
Last photo:
Join Date: Jun 2003
Location: Espaņa Right Coast
Posts: 3,259
Wiki Edits: 0

Thanks: 90
Thanked 92 Times in 78 Posts
If thatīs a Speed Demon you have you need 18š-24š initial timing.
The Manual.
Turn the carb upside down and check the throttle blades are correctly set, all four.
I found with my Speed Demon it was a case of tweak, tweak and tweak again.
Even so Itīs a great carb.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-11-2008, 04:59 AM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,654
Wiki Edits: 0

Thanks: 15
Thanked 58 Times in 55 Posts
This sounds like a issue I faced a few years back. Remove the carb and look in the plenum, if you see any oil in the plenum you have a vacuum leak on the intake manifold. This will cause weird rich lean patterns as you`ve found. Although it may not be the issue with yours but it was mine.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-11-2008, 10:57 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,753
Wiki Edits: 0

Thanks: 4
Thanked 419 Times in 361 Posts
Quote:
Originally Posted by Jonas.snall
Thank you Bogie,

Yes I think I am talking about total timing.

The sparkplugs number 2, 4, 6, and 8 looks like 1 and 3. They are white. So I have tried with both go up in jets and adjusting of the ideal screws. But the lean condition will not go away apart from plug 5 and 7 which are black. And they have always been that way since I started up this engine the first time 4 month ago.

Do you think it can be a fuel distribution problem? I will try checking the fuel pressure to night. Or can it be the demon?

And thank you Bogie for your response!
Are all the plugs the same part number, leading to them being the same heat range and resistive or not.

White insulators would show either not much usage since new, a lean mixture, too much advance, to hot of a heat range.

The black plugs could be a fuel puddling or distribution in the manifold, jetting would not have an effect if this was happening. But aside from a manufacturing error, Edlebrock is a very through organization and rarely sells stuff that isn't right. Other possibilities for those two:

- Cam lobes wiped out

- bad ignition wires

- plugs damaged on installation, if you have headers it's always a risk that in the tight quarters the plugs could have been cracked when wrenching them in place. Ask me how I know, go ahead, I dare ya!

- plugs defective from the manufacturer

- blown head gasket, a real possibility given that these are in adjacent cylinders. Do a compression test, low and the same is good indicator.

Bogie
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-13-2008, 02:13 PM
Registered User
 
Join Date: Sep 2008
Location: Sweden
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for all your answers.

I have now done a compression test and all cylinders are between 11 and 12 psi and the fuel pressure is constantly at 8 psi. Is 8 maybe a little bit too much?

However I did run the car for maybe 15 minutes. The oxygen display still shows on both rich and lean. Nearly all the lamps in the Edelbrock display are on. After the run I unscrewed the plugs. Number 5 and 7 is not as black as they use to be. In general, for all plugs, the electrode is white but there is an area little bit down on the plug that is brown and everything below that is all black. Maybe if I run the car for an hour I will get the correct color on the plugs?

How can the Edelbrock display show on both rich and lean? Is the engine that bad? The display is showing this on ideal, cruise and full throttle.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 09-13-2008, 02:19 PM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,654
Wiki Edits: 0

Thanks: 15
Thanked 58 Times in 55 Posts
A carb should not have more than 5 psi for a street application. This could be where the root of your issue is. Have you checked the carb at idle to see if fuel is dripping out the boosters? Or does white smoke pour out the carb after you shut it down? this is signs the fuel pressure is too high.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 09-13-2008, 02:35 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by Jonas.snall
Thanks for all your answers.

I have now done a compression test and all cylinders are between 11 and 12 psi and the fuel pressure is constantly at 8 psi. Is 8 maybe a little bit too much?

However I did run the car for maybe 15 minutes. The oxygen display still shows on both rich and lean. Nearly all the lamps in the Edelbrock display are on. After the run I unscrewed the plugs. Number 5 and 7 is not as black as they use to be. In general, for all plugs, the electrode is white but there is an area little bit down on the plug that is brown and everything below that is all black. Maybe if I run the car for an hour I will get the correct color on the plugs?

How can the Edelbrock display show on both rich and lean? Is the engine that bad? The display is showing this on ideal, cruise and full throttle.
Does your Edelbrock unit use 2 sensors, or just 1?

Most I have seen use only one, and it's switching between rich and lean is normal. As stated above, 8 psi fuel pressure is too much. You should be running between 5 to 6 psi, around 5.5 psi is best.
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
running rich or lean inquiring_mind2 Engine 2 04-25-2008 05:35 AM
running lean or rich stoney 81ta Engine 6 04-14-2007 04:08 PM
Lean or Rich McDuff Engine 3 02-09-2006 11:51 AM
Lean or Rich??? MEAN_SBC Engine 29 10-22-2004 08:53 PM
Would you guess it's runnin rich or lean stonedchihuahua Engine 16 07-08-2003 07:06 PM


All times are GMT -6. The time now is 11:16 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.