Big Block misses and pops - 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 01-08-2011, 08:30 PM
Registered User
 
Join Date: May 2009
Location: Clark, SD
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Big Block misses and pops

454 chevy with HEI giving me fits. Missing, popping thru exhaust bad on pass side, ocasionally backfires thru carb, have checked spark, timing, pulled valve cover to see if I had broken valve spring. Bad cam? Not a pro but know that if running rough and backfiring thru carb a lot of times is indicating bad cam.

Thoughts?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-08-2011, 08:52 PM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,655
Wiki Edits: 0

Thanks: 15
Thanked 59 Times in 56 Posts
Pop the valve covers and fire it up. Carefully eye all the rockers. If you see one or more barely moving compared the others the cam is history.
If the cam is okay, then check the voltage going to the HEI with the engine running. A HEI must get a solid 12 volts or more. They will run on as low as 8 volts, but popping and backfiring is the result. Also make sure there are no crossed plug wires. 5 and 7 run side by side on the block as well as on the distributor and are very easy to cross up.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-09-2011, 03:43 AM
Registered User
 
Last photo:
Join Date: Mar 2010
Location: USA
Posts: 218
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
On my HEI, the little plug that goes from the shaft to the cap was a bit loose for all three wires. I resoldered the wires and crushed the ends so it was tighter to slide on, now the car runs alot better. Also when I took my plug wires off and reinstalled them, the number 8 plug wire boot was on the plug, the the metal connector slid back inside the boot and i didnt realize it, the result was horrible running.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-09-2011, 10:25 AM
Registered User
 
Join Date: May 2009
Location: Clark, SD
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks

I appreciate your input, I did spin it over with the valve cover off and all valves seem to be moving equally. Car ran fine, until we came home from a car show and fired it up to unload from the trailer and it started to miss so it seems that the issue started all of a sudden. Did pull the cap and rotor to see if I had a bad cap or burned spot on the rotor and all looked fine. Will check the current to the dist and make sure I have 12 volts.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-09-2011, 12:08 PM
Registered User
 
Last photo:
Join Date: Apr 2010
Location: Sand Rock
Posts: 392
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
hmmm, kinda sounds like a bent valve? never can tell, i had a 454 and when the rotor button was time to change, it did some popping through the pipes!
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 01-09-2011, 01:20 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by bowtieguyss
I appreciate your input, I did spin it over with the valve cover off and all valves seem to be moving equally. Car ran fine, until we came home from a car show and fired it up to unload from the trailer and it started to miss so it seems that the issue started all of a sudden. Did pull the cap and rotor to see if I had a bad cap or burned spot on the rotor and all looked fine. Will check the current to the dist and make sure I have 12 volts.
Was the car left w/the hood open w/o an air filter?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-09-2011, 01:51 PM
Registered User
 
Last photo:
Join Date: Mar 2008
Location: Arkansas
Age: 51
Posts: 298
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Have the modules in the dist. checked. Sometimes after they heat up they will malfunction.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 01-09-2011, 02:50 PM
Registered User
 
Join Date: May 2009
Location: Clark, SD
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
No, the air cleaner has not been off. Will have to do a compression test, that should tell me if I have a bent valve. Like I said, it went from running fine when shut off to missing when restarted. Seems to only pop out of the pass side pipe so the issue certainly seems to be to that side.
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
backfire at startup, now misses under load blue400 Engine 8 09-09-2013 08:04 PM
recurved distributor now misses under throttle blue400 Engine 41 09-29-2010 02:03 PM
New engine misses at idle only Muley Engine 4 01-28-2004 09:52 PM
305 misses and pops Tom Welshans Engine 6 12-12-2003 08:29 AM
Chevy 305 pops and misses Tom Welshans Engine 12 11-13-2003 10:47 AM


All times are GMT -6. The time now is 09:25 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.