Catalina Backfire - 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 06-11-2009, 02:03 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 666
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
Catalina Backfire

I have a 66 Catalina with a 69 428. I just installed the Pertronix ignition and converted back to a Qjet from an AFB. I always have had some popping out of the tail pipe. It was good for parades to rev the engine and hear the following pops. Now it pops when I hit the gas. The wires are in correct order. The timing is correct as far as I know. There is no indication of valve problems based on the vacuum gauge. Could this be lean conditon?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-11-2009, 05:09 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 Mertz
The timing is correct as far as I know. There is no indication of valve problems based on the vacuum gauge. Could this be lean conditon?
Retarded timing will get you backfiring on deceleration, no doubt. You should put a timing light on it to know exactly what your timing- both initial and total- is set at.

Check the plugs after a run to see what they tell you AFA the carb being lean.

Be aware that some non-diagnostic type vacuum gages are damped to keep the needle from fluctuating- exactly what you DON'T want when diagnosing an engine. Be sure your gage is one meant for the purpose. Because a valve sealing or cam lobe problem could be at the root of it all.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-11-2009, 06:45 PM
riceharvester's Avatar
Registered User
 
Join Date: Jun 2009
Location: home
Age: 33
Posts: 34
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Mertz
I have a 66 Catalina with a 69 428. I just installed the Pertronix ignition and converted back to a Qjet from an AFB. I always have had some popping out of the tail pipe. It was good for parades to rev the engine and hear the following pops. Now it pops when I hit the gas. The wires are in correct order. The timing is correct as far as I know. There is no indication of valve problems based on the vacuum gauge. Could this be lean conditon?
Its the carb. Swap back and see what happens....
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-12-2009, 02:08 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 666
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
I have set the timing with a timing lite. I am thinking now that the damper might have slipped. I will check for top dead center and make sure it is correct. The manual calls for 8 BTDC if it is a low hp motor and 12 if it is high hp motor. I have it set as high as I thought was ok. I had some popping out of the tailpipe with the AFB as well. It didn't happen while hitting the gas however. The AFB was a 650.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-12-2009, 02:22 PM
Registered User
 
Join Date: Jun 2009
Location: Detroit
Posts: 14
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Set your timing to 8 BDTC.... I know everyone want's to pretend they have a race car...

But your in diagnostic mode...so stop pushing the envelope until you know everything is working perfectly in a standard state....give yourself a solid starting point before you start making adjustments.

Set your timing back and make sure your carb is setup correctly as well.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-12-2009, 02:40 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 Mertz
I have set the timing with a timing lite. I am thinking now that the damper might have slipped. I will check for top dead center and make sure it is correct.
Good idea to check the outer ring on the damper.

Were you able to determine that your mechanical advance is working? As in- the timing advancing with the engine speed increasing, w/the vacuum advance disconnected?

Is the vacuum advance working and hooked up?

There's a tutorial for making a timing tape HERE that you can use to see what your total timing is at, in case you don't have access to an adjustable timing light.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 06-12-2009, 09:34 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 666
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
I have an adjustable timing lite. I restarted it today and it is running better but now it is backfiring and afterfiring. I have been using regular gas and might try some octane booster. I might have some water in the gas from sitting this winter. Carb is set at 2.5 turns out.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 06-15-2009, 09:37 PM
Member
 
Last photo:
Join Date: May 2003
Location: Shreveport LA
Age: 64
Posts: 5,103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
How old is the gas?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 06-16-2009, 02:21 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 666
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
That may be the problem. I had older gas in it for a few years but have since added new gas (last fall). I am using regular with 10% ethanol. I am going to try adding some premium or toluene.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 06-16-2009, 03:21 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 Mertz
That may be the problem. I had older gas in it for a few years but have since added new gas (last fall). I am using regular with 10% ethanol. I am going to try adding some premium or toluene.
I would stick to premium. It will be as good as it needs to be, short of good ol' 100 octane from "BITD".
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 06-22-2009, 02:17 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 666
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
I added toluene to the gas and tried tuning it again. I discovered that my Qjet doesn't have a vacuum port that doesn't have manifold vacuum at idle. Disconnecting the vacuum advance the base timing was at 4 BTDC. With vacuum it was at 10. I am reading about 15 in of vacuum. I tried setting the timing by vacuum and managed 17 but but that put the readings of the mark on the balancer. It ran better and no backfire or afterfire when I rev'd it. The idle would drop off quickly if I retarded it past a certain point. The was a small range that it ran well in. The cap and rotor are new. I thought I had solved the problem until I got in and rev'd the thing with the pedal and the backfire and after fire were back in a big way. Vacuum is steady but I still think it might be valves.

The Qjet in one made by Carter that starts with 170. (I forgot to bring in the number this morning) Is something wrong with the carb if it doesn't have a port without vacuum at idle. There is no choke on it so I rigged a manual choke of the lever on passenger side. The engine starts good. but had a bit of trouble with the restart after the timing change indicating I went to far. I set it back a little and it started better.
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 thru carb airraptor Engine 11 06-12-2009 02:30 PM
Engine backfire fred56 Engine 3 06-04-2006 11:01 AM
Small backfire from Carb...Chevy 350 interro1 Engine 7 07-15-2005 02:00 PM
Backfire geostang351 Engine 4 05-28-2005 09:17 PM
4.3L V6 1986 Chevy- bogging and backfire firebird_red Engine 12 05-03-2005 03:34 PM


All times are GMT -6. The time now is 08:52 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.