'86 GMC carb problem - 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 10-21-2004, 03:17 PM
johnnymopar's Avatar
Love your nails! You must be a Libra
 
Last photo:
Join Date: Dec 2001
Location: Stratford, ON, Canada
Posts: 599
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
'86 GMC carb problem

i have a '86 GMC 1/2ton w/4.3 V6 and Q'jet carb. i recently bought the truck and decided to rebuild the carb because the truck idled rough and wouldn't start after sitting for a few days.

so i got the carb rebuilt and it starts right up, but now it idles too high and i've got the idle backed right off. the truck is also dieseling now and i'm thinking it's a combination of high idle and timing.

so i guess what i want to know is does anybody know what my timing should be set at and what would cause the engine to idle too high when the throttle plates are closed?

another thing about this carb is that it is a 4bbl but it looks like there is a pin on the secondary plate rod and a cam on the side of the carb that locks out the secondaries. what's up with that?

thanks,

JB

    Advertisement
__________________
"Well done is better than well said." - Benjamin Franklin (1706-1790)
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-21-2004, 04:12 PM
Tazz
 
Last photo:
Join Date: Jun 2001
Location: amherst,ohio
Age: 66
Posts: 2,049
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sounds like timing is way off and throttle stop out of adjustment!! CK here: www.chevytalk.com/


Tazz


Rat Rods Rule!
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-21-2004, 10:59 PM
sbchevfreak's Avatar
Licenced Automotive Technician
 
Last photo:
Join Date: Feb 2004
Location: Land of big Easter eggs, Alberta
Age: 34
Posts: 1,604
Wiki Edits: 0

Thanks: 8
Thanked 9 Times in 9 Posts
try pushing the secondary throttle closed. they have been known to stick slightly open and cause an unadjustable high idle. That lock out cam, if it is on the choke side of the carb, is there to block the secondaries from opening while the choke is on. (if i'm thinking of the right cam! )

Your dieseling could be caused by carbon buildup on in the engine, and the high idle is keeping it hot, giving you a source of ignition after the key is off.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-22-2004, 02:29 PM
johnnymopar's Avatar
Love your nails! You must be a Libra
 
Last photo:
Join Date: Dec 2001
Location: Stratford, ON, Canada
Posts: 599
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
thanks guys.

sbchevfreak, i think you might be right on the choke cam thing. if i remember right the cam pivots on the same spindle as the choke. just when i looked at it on the bench it didn't look like it would move at all, it looked like it was wedged in there on purpose so the secondaries wouldn't open at all.

we'll see how it goes.

thanks,

JB
__________________
"Well done is better than well said." - Benjamin Franklin (1706-1790)
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



All times are GMT -6. The time now is 01:35 PM.


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.