Holley rich at idle - 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
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 12-30-2005, 07:38 AM
pcesak's Avatar
Last photo:
Join Date: Jun 2002
Location: Houston, Texas
Posts: 64
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Holley rich at idle

Hapy New Year. I have a '35 Chevy with a SBC400 in it. I have upgraded to Allum heads (Dart Pro) and Edelbrock Air Performer and a Holley Avenger 750. Engine runs great and strong from about 1800 RPMs to 4500 RPM's. For an old guy, I go fast enough at the 4500 top end.

My problem is that my car runs entirely too rich at idle with massive amounts of unused gas coming out the exaust. If I manually floor the carb from idle, it will sometimews backfire but always seems to just momentarily die. If I moderately increase the throttle, it works great and is using every bit of gas it can get. I was told to increase the jets but won't that increase the richness at idle also. Any help would be appreciated.


Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 12-30-2005, 08:17 AM
larryblack's Avatar
Certified Lead Foot
Last photo:
Join Date: Jan 2003
Location: Houston, TX again
Age: 65
Posts: 520
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
You may be running too low vacuum and the power valve circuit is opening or your throttle blades have uncovered the transistion circuit.

Part of the backfire is due to insufficient accelerator pump response to the opening of the throttle.

Have some one hold the gas pedal floored. On the accel arm is an adjustment. You need to have 15 to 20 thou of clearance between the lever on the bottom of the bowl and the spring assembly.

I have found the pink cam I think #330 in the number 2 hole on the shaft and #3 hole on the cam with a 31 discharge nozzle usually a good starting point.

Measure your vacuum and the power valve should be 1.5 to 2.5 smaller than the idle vacuum. To get the throttle blades to close and cover the transistion circuit, you can slightly open the secondary blades or drill small holes in the primary blades to allow more air flow with less opening.

There are a number of HOLLEY tuning manuals around. I suggest you pick one up, read it cover to cover.
Reply With Quote Quick reply to this message

Recent Engine 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:
Please select your insurance company (Optional)


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
holley too rich at idle on 400 camino_man Engine 9 11-14-2005 04:12 PM
I'm going to make a bonfire out of my car blown69stang Engine 36 08-22-2005 03:36 PM
Performance cam with a 2 corner idle Holley DP 650 Mad Maggot Engine 15 08-02-2005 06:04 AM
Idle adjustment - holley 650 dp 4777 Toyman Engine 5 07-30-2005 07:07 PM
running super rich at idle??? ocbaud Engine 4 11-21-2004 02:21 PM

All times are GMT -6. The time now is 01:48 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, 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 © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.