Blower back fire. - 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 10-14-2012, 03:30 PM
Registered User
 
Join Date: Oct 2012
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Blower back fire.

I am having a problem with my 426 cube inch motor . the motor has a bds blower systems with two 650 carters on top . W hat is going on is at an idle the motor run fine . Once I drive the car on the street i get passed one third throttle the motor back fires in the blower . I have retarted the timing to 32 d. total still have same problem . Also I have installed a HUASE FUEL PUMP . I STILL HAVE THE SAME .Help there must be some one out there that has run into this problem .

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-14-2012, 03:34 PM
T-bucket23's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Engine basic condition - how to check Last photo:
Join Date: Aug 2005
Location: Massachusetts
Age: 57
Posts: 5,155
Wiki Edits: 26

Thanks: 7
Thanked 109 Times in 94 Posts
Start with checking the float levels. It sounds like you are going lean. Make sure both carbs are actually getting fuel. If the secondary one is not it will lean out as soon as the blades begin to open.
__________________
Artificial Intelligence is no match for Natural Stupidity



Chet
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-14-2012, 03:57 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,898
Wiki Edits: 326

Thanks: 751
Thanked 985 Times in 831 Posts
Quote:
Originally Posted by ED WALCOT View Post
Also I have installed a HUASE FUEL PUMP
I have no idea what this is. Can you be more specific? Have you monitored the fuel pressure at the carb inlets? Is this a late Hemi (426)?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-14-2012, 06:00 PM
BOBCRMAN@aol.com's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Holly, michigan
Posts: 8,121
Wiki Edits: 0

Thanks: 25
Thanked 266 Times in 249 Posts
Power enrichment (power valves if it was Holley) systems are not getting correct signal or jetting too lean
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-14-2012, 06:03 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,052
Wiki Edits: 0

Thanks: 3
Thanked 367 Times in 361 Posts
Incorrect timing curve for a roots style blower motor.
Blower motors love lots of timing at idle. but conservative timing when under boost WOT.
the timing curve is a lot different than a N/A motor.
lack of idle timing makes it back fires thru the carbs. and generally load up and run like pooo.


lack of fuel system fuel flow (you are staving the carbs for fuel) under boost heavy throttle and or lean carb jetting.

The bigger the camshaft the more the blower motor will want generous timing at idle.
Many blower motors want full locked out timing 34-36deg at idle and part throttle
but need the timing to retard progressively as throttle and boost is added WOT.
that what a boost retard box is for.

typcial is 34-36deg at idle and part throttle light cruise and progressivily retards to 26-28-30deg timing under boost depending on the boost- compression ratio and fuel octane used.

a stock timing curve will not work. You need to double the fuel flow volume
fuel pump(s) volume fuel lines size
filters and fittings size tank pick up tube(s) are all critical. stock stuff will not work.

stock carb jetting will not work. metering rod power step spring choice is critical.
start with the sfiffest spring 8" vacuum rated.
750cfm carbs are best. for a ton of reasons. Blowers need big carbs.

stock jetting for a N/A motor will not work.

start carb jetting tuning plenty rich and work from there. Lots of fuel flow volume. not high pressure.
fuel pressure 6psi. two carter p4070 fuel pumps 72GPH rated each work really good thru two separate 3/8" fuel lines.
once for each carb.

what cam? what blower what pulley ratio?

Last edited by F-BIRD'88; 10-14-2012 at 06:10 PM.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-14-2012, 08:05 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,052
Wiki Edits: 0

Thanks: 3
Thanked 367 Times in 361 Posts
Its very likely the spark plugs are now carbon-fuel fouled and will need to be replaced.
Blower motors tend to like a spark plug that is slightly cooler heat range than
what you would using in a stock motor. 2 to 3 heat ranges cooler.
Racing plugs are not used on the street. Too cool .. Hot plugs are not used. Too hot (detonation, priignition)
Ignition faults and vacuum leaks must be eliminated. blower intake gaskets.
When the timing curve and carbs are set up right the plugs will no longer foul and the
backfireing and poor drivability will be cured.
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
back fire in the carb P.H. 88 Engine 8 02-14-2010 10:50 PM
back fire say10tatoo Engine 7 02-05-2005 10:41 PM
back fire savman1 Engine 10 06-18-2004 03:58 PM
back fire DoubleVision Engine 2 12-24-2002 12:47 PM
motor back fire DESPERADO Engine 3 07-09-2002 02:26 PM


All times are GMT -6. The time now is 08:01 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.