69 BB Backfire through exhaust - Corvette Forum : DigitalCorvettes.com Corvette Forums
 
 
Go Back   Corvette Forum : DigitalCorvettes.com Corvette Forums > C3 Corvette Forums > C3 Corvette
Register Forums Garage Garage Mark Forums Read Auto EscrowInsurance Advertise

Notices

C3 Corvette
C3 Corvette General | Technical | Performance | Aftermarket | Discussions

Other sections:
Corvettes Classifieds
Corvette Detailing & Car Care
Corvette Audio/Video/Radar
General Automotive/Shop/Tools
Corvette Performance Driving/Racing

( Sponsored by: Zip Corvette Parts )

Shops/Tuners
Custom Image Corvettes
A&A Corvette
Corvette tuner

Interior
Corvette aftermarket products

Insurance



Parts & Products
Race Ramps
Edelbrock
ATI/Procharger
Corvetteguys.com
Melrose Motorsports
Parts Taxi
Airaid
Pfadt Racing
Madvette Motorsports
Hi-tech Custom Concepts
Corvette Garage
Corvette Parts and Accessories
Corvette Car Care Products
Corvette HID

Tracks/Schools
Bob Bondurant School of High Performance Driving
Corvette driving school

Wheels/Tires
Cray Wheels

Services
BADWERKS.com
Reply
 
Thread Tools
Old 07-14-2019, 11:55 PM   #1
NJAus
DC Crew
 
Posts: 4
Member #181186
Member since: Mar 2019

Thanks: 1
Thanked 0 Times in 0 Posts
69 BB Backfire through exhaust

Hi All,

I have a 69 BB that was running fine with the exception that when the throttle was blipped and it idled down, the car would stall.

Turns out the car was running lean and the mixtures were adjusted to richen it up a tad using a gas analyzer.

As soon as I got the car back I noticed loud noises in the rear and hesitation under partial and full throttle, most likely backfire (after fire) out the exhaust. I think there was a backfire out the carburetor also but no where as loud as out the exhaust.

I have taken the car back to the engine tuner to have a look at, what should he be doing (I am not an expert but I want to make sure I ask a few questions to ensure the problem is sorted)?

I think he mentioned increasing primary jet size? When this is done does the car need the timing adjusted again?

The car has an aftermarket cam and does not run vacuum advance.

Thanks.
NJAus is offline   Reply w/quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 07-15-2019, 11:23 AM   #2
7TRoadster
DC Crew
 
7TRoadster's Avatar
 
Posts: 1,773
Member #106320
Member since: May 2010
Location: Kennewick, WA

My Corvette(s)
1970 Roadster, Mast Motorsports LS7, TKO 600, SS Frame, C4 suspension

Thanks: 44
Thanked 162 Times in 144 Posts
Under normal conditions there is usually some fuel that isn't completely burned in the exhaust. The first half of a backfire out the exhaust is caused when this fuel gets ignited. The second half of the backfire is oxygen, this unburnt fuel has to have oxygen to ignite.

If running lean there is more air than fuel in the mix, the engine will burn all the fuel and expend left over oxygen into the exhaust. Don't overlook the possibility of a vacuum leak, very typical on these cars and can wreak havoc on the way the engine runs.

Ritchen the mix and you compensate for the leak but only at low engine rpm. They then usually run like crap until you get enough rpm to overcome the leak.

Just an old man's $0.02
7TRoadster is online now   Reply w/quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Corvette Forum : DigitalCorvettes.com Corvette Forums forums, you must first register.
Please enter your desired user name (12 CHARACTERS MAXIMUM), 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:
City / State / Country?
Where you live
What kind of Corvette(s) do you own?
This field is not required.
Insurance
Please select your insurance company (Optional)

Log-in


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

Forum Jump

Powered by vBadvanced CMPS v3.2.2

All times are GMT -6. The time now is 02:23 PM.




Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
2003-2011, DigitalCorvettes.com - All Rights Reserved