I'm stumped - backfiring
Thread Starter
Race Director
Joined: Dec 2007
Posts: 14,345
Likes: 4
From: Hartselle AL
St. Jude Donor '09
I'm stumped - backfiring
Just completed the hydroboost & Borgeson mod. That all went relatively smooth.
Start it up and I've got an intermittent backfire at idle and higher rpms. It primarily (95%) is backfiring through the exhaust with the odd pop through the carb.
What I've done/checked so far:
- Put vacuum gauge on several locations. Holds a rock steady 15hg at idle. No fluctuation at all.
- Sprayed carb cleaner everywhere - absolutely no change in idle speed.
- Installed new plug wires.
- Double checked timing.
Can an exhaust leak at the headers cause this type of backfire? I ask because I pulled the left headers for the above install and reused the old header gasket (I know....)
It ran fine prior to the disassembly/reassembly.
Details: '78 L-82, stock carb, intake, HEI. Headers with true dual & x-pipe.
Start it up and I've got an intermittent backfire at idle and higher rpms. It primarily (95%) is backfiring through the exhaust with the odd pop through the carb.
What I've done/checked so far:
- Put vacuum gauge on several locations. Holds a rock steady 15hg at idle. No fluctuation at all.
- Sprayed carb cleaner everywhere - absolutely no change in idle speed.
- Installed new plug wires.
- Double checked timing.
Can an exhaust leak at the headers cause this type of backfire? I ask because I pulled the left headers for the above install and reused the old header gasket (I know....)
It ran fine prior to the disassembly/reassembly.
Details: '78 L-82, stock carb, intake, HEI. Headers with true dual & x-pipe.
Burning Brakes
Joined: Oct 2007
Posts: 816
Likes: 107
I am unfamiliar with the mod you have done..... what did you have to do to install it?
Reusing header gaskets is no big deal I have done it plenty and no a leaking header gasket will not cause your issue.
Double check your plug wires to make sure they are all correct........I have crosed 3-5 before it is an easy mistake to make and will cause an issue as you describ.
Reusing header gaskets is no big deal I have done it plenty and no a leaking header gasket will not cause your issue.
Double check your plug wires to make sure they are all correct........I have crosed 3-5 before it is an easy mistake to make and will cause an issue as you describ.
Thread Starter
Race Director
Joined: Dec 2007
Posts: 14,345
Likes: 4
From: Hartselle AL
St. Jude Donor '09
I am unfamiliar with the mod you have done..... what did you have to do to install it?
Reusing header gaskets is no big deal I have done it plenty and no a leaking header gasket will not cause your issue.
Double check your plug wires to make sure they are all correct........I have crosed 3-5 before it is an easy mistake to make and will cause an issue as you describ.
Reusing header gaskets is no big deal I have done it plenty and no a leaking header gasket will not cause your issue.
Double check your plug wires to make sure they are all correct........I have crosed 3-5 before it is an easy mistake to make and will cause an issue as you describ.
That's exactly the bonehead thing I did. #2 & #4 were crossed. My brother stopped over for a visit and a second set of eyes helped.
Now to figure out why my clutch won't adjust & work correctly. Its like it is not traveling far enough to completely disengage. I hope I don't need to do a clutch & throw out bearing job right now.
Thanks for the response.
