Engine Backfire - Impala Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools
post #1 of 5 (permalink) Old 04-10-2016, 09:25 PM Thread Starter
Member
 
Join Date: May 2010
Location: California
Posts: 89
Blog Entries: 1
 
Engine Backfire

I have what appears to be stock 350 SBC with shorty headers, HEI distributor, 1405 Edelbrock carburetor. Not sure of the internals because I purchased the motor as is. I have it mated to a 350 trans and they are both sitting in a 1964 Impala SS HT.

While driving up a hill one day, I began to hear the engine backfire in rapid succession. I figured the carb was the cause so I inspected it and found nothing. I checked the time and made sure that it was where it needed to be and still nothing, engine kept back firing.

A friend if mine suggested that I check the rocker arms so I did. I found that the number 8 was extremely loose. Its the one closest to the back of the motor on the passenger side. I went ahead and tightened it up until it felt like the rest of the other ones and the backfiring stopped.

Thinking I fixed the issue, I drove the car like that for about 50 miles and it has started to do the same thing again. I popped the valve cover and the same rocker arm is now loose and backfiring again.

What do you gentlemen think is causing the rocker arm to come loose to the point where it is cause the 8 piston to backfire? All recommendations are welcome.


Hector,

Semper Fi,

Hector

1964 Impala SS HT
2007 Tahoe LTZ
2006 Kawasaki ZX10
2003 Yamaha R1 (sold)
1995 Impala SS
1993 Tahoe GT (sold)
1978 Buick Regal (sold)
sandiegohat is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 04-11-2016, 01:28 PM
Member
 
Join Date: Aug 2014
Location: Netherlands
Posts: 51
 
It's possible that the rocker arm stud is working itself loose from the head, don't know if it's pressed or a screw in stud though.
Dennis J is offline  
post #3 of 5 (permalink) Old 04-11-2016, 03:11 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,840
 
It could be a cam lobe going bye bye as well as a a pressed in stud pulling loose. If it is a loose stud a straight edge laid across the top of the studs will tell you quickly enough. They should all be the same height. A cam lobe dying will keep loosening up until it stops moving all together.


Back firing is usually a timing issue, but it can also be caused by your engine running too lean.


Big Dave
Big Dave is offline  
 
post #4 of 5 (permalink) Old 04-12-2016, 04:09 PM Thread Starter
Member
 
Join Date: May 2010
Location: California
Posts: 89
Blog Entries: 1
 
Quote:
Originally Posted by Big Dave View Post
It could be a cam lobe going bye bye as well as a a pressed in stud pulling loose. If it is a loose stud a straight edge laid across the top of the studs will tell you quickly enough. They should all be the same height. A cam lobe dying will keep loosening up until it stops moving all together.


Back firing is usually a timing issue, but it can also be caused by your engine running too lean.


Big Dave
Big Dave, I'm going to lay a straight edge on it tonight and see what that tells me. I tightened down the nut and she stopped back firing. How do I check if she is running to lean?

Semper Fi,

Hector

1964 Impala SS HT
2007 Tahoe LTZ
2006 Kawasaki ZX10
2003 Yamaha R1 (sold)
1995 Impala SS
1993 Tahoe GT (sold)
1978 Buick Regal (sold)
sandiegohat is offline  
post #5 of 5 (permalink) Old 04-12-2016, 08:24 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,840
 
Read the plugs. They should be a light tan with a brown "fire ring" on the porcelain where the flame front stops. There are pictures showing the many maladies and a picture is worth a thousand words in this instance. The plugs were the only way to know what was going on inside the engine before Knock sensors and Oxygen sensors where used with EFI cars.


These sensors can be adapted to non-computer controlled cars but the information won't do much good as you could loose an engine before you reacted to the signal. Computers (the engine's electronic control unit is usually one of many computers dedicated to keeping your car running and not polluting) check the engine to see what it is doing tens of thousands of times a second. I use an oxygen sensor to tune my car's engine but when I was trying to adapt a knock sensor to my MSD ignition box I was unable to rig up the knock sensor to retard my timing the way a computer does it in a modern car (as I have only three wires to play with which when programing an analog computer doesn't result in too many lines of code).


I think the best plug reading info (pictures) were on NGK's web site, but I haven't looked in a while.


Big Dave
Big Dave is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Impala Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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

 
For the best viewing experience please update your browser to Google Chrome