305 ignition timing issues - 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> Electrical
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 02-04-2008, 02:27 PM
Registered User
Join Date: Feb 2008
Location: York, PA
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
305 ignition timing issues

Hey everyone.. im new here, ive been checking out the site for a few days and I really like it here. Was wondering if you all could give me some much needed input on the problem im having...

I have a stock 305sbc with an intake and 4bbl Q-jet from an old 350. I took the carb apart and its clean and in tact. When the engine is not in gear it free revs without a problem. My issue is that i am getting a backfire up through the carb while i go down the road and mash the throttle. Now i seen a few threads on here that say its a lean side effect. Not sure if thats possible since the carb is off of a 350.. but i could be wrong... anyway, as of right now my timing is set at 4 degrees btdc and i have tried all the way up to 12 degrees btdc. My spark plugs (from my opinion) dont look too bad. I have also adjusted the valves in the engine and still the same problem. Only other things i can think of is a. a rounded cam lobe (but i didnt notice anything out of the ordinary while adjusting the valves), b. something is up with the distributor (maybe the mechanical weights .. not sure what to check for there though) or c. i screwed up the valve timing when i replaced the timing chain and gears.

Sorry this is so long. If anyone could give some feedback it would be greatly appreciated. Thanks


Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 02-05-2008, 09:14 PM
Registered User
Last photo:
Join Date: Jan 2002
Location: PA
Posts: 82
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts

Timing: Hook up your timing light, slowly open the throttle while watching your timing marks. Your timing should advance when rpm goes up. If nothing moves by 3500, then your advance is stuck (not uncommon on HEI distributors.

It might be clean but your accelerator pump might be hard as a rock and not sealing tight enough, or the orifices may be gummed up, not giving you any pump shot when you open the throttle. With the engine off and air cleaner off, look down the primaries of the carb, while opening and closing the throttle. You should see 2 equal streams (like an old fashion squirt gun) of "pump shot" when you rapidly open the throttle.

Good luck
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-06-2008, 08:59 AM
Join Date: Jul 2005
Location: Montana
Posts: 98
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
If its only happening under load, My first suspect would be a bad plug wire.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-08-2008, 05:05 PM
Registered User
Join Date: Feb 2008
Location: York, PA
Posts: 2
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for the support!

I bought a rebuild kit for the carb, cleaned it up and put it back together. The engine ran better but still was sluggish. So I hooked up the timing light, disconnected the vacuum advance and reved up the engine to see if there was any change in the timing... and there wasnt. That tells me the mechanical advance is not working properly. So tomorrow Im going to take out the distributor and see if I can get it to work right.. Wish me luck and thanks again for the help!!
Reply With Quote Quick reply to this message

Recent Electrical 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
454 Ignition Timing Question leejoy Engine 56 09-13-2008 08:40 AM
Ignition timing, Jeep 4.0 ChevelleSS_LS6 Engine 0 10-26-2006 06:20 PM
Timing issues i think Wmurp4 Engine 4 08-13-2006 03:27 PM
ignition timing (in relation to rpms) KNanthrup Engine 8 05-21-2006 04:16 PM
Timing issues ttitans1 Engine 16 01-10-2006 08:11 PM

All times are GMT -6. The time now is 02:29 AM.

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.