Backfiring Problem...any suggestions?
Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
Backfiring Problem...any suggestions?
I was wondering if anyone could help me out. I'm not the greatest mechanic and cant seem to fix this. I get backfire through the carburetor, i've just about have no power on the road (especcially up hills) and the engine diesels real bad when i try to shut it off. 
so far i've changed the spark plugs, checked the timing, all plug wires are wired correctly, the distributor, wires, and ignition coil are new. is it a carb tuning or something??? I'm all ears if anyones got a suggestion. 
so far i've changed the spark plugs, checked the timing, all plug wires are wired correctly, the distributor, wires, and ignition coil are new. is it a carb tuning or something??? I'm all ears if anyones got a suggestion.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Backfiring through the carburetor is a lean condition. Check to see if the accelerator pump is supplying fuel. No power on grades could also be a lean condition. The power piston could be stuck, float level could be low, could have trash in jets. The run on could be timing related. Retarded timing contributes to run on.
BigBlockk
Later.....
BigBlockk
Later.....
Pro
Joined: Nov 2004
Posts: 659
Likes: 0
From: Flower Mound Texas
Originally Posted by kaymonster
I was wondering if anyone could help me out. I'm not the greatest mechanic and cant seem to fix this. I get backfire through the carburetor, i've just about have no power on the road (especcially up hills) and the engine diesels real bad when i try to shut it off. so far i've changed the spark plugs, checked the timing, all plug wires are wired correctly, the distributor, wires, and ignition coil are new. is it a carb tuning or something??? I'm all ears if anyones got a suggestion.
so far i've changed the spark plugs, checked the timing, all plug wires are wired correctly, the distributor, wires, and ignition coil are new. is it a carb tuning or something??? I'm all ears if anyones got a suggestion. 
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
If the distributor were 180 degrees off, the engine wouldn't run.
Backfiring through the carb is likely a timing issue. If you've checked your timing and it appears to be set to specs, you may have a harmanic balancer with a spun outer ring giving you bad readings. Also, I'm assuming your plug wire are properly routed,..right?
For now, retard the initial timing until you eliminate the backfiring problem (turn the distributor clockwise).
The dieseling is likely caused by the throttle blades being open too much at idle. But if you retard your inital timing you'll have to open the TB's further to maintain your idle speed which will aggravate the dieseling prob.
So, I'd switch to manifold (full-time) vacuum (if not already) which will mean you'll need less of a throttle blade opening at idle. If this is q-jet carb, use the port on the passenger's side of the carb.
Also, if this is an old, tired engine with poor compression, your throttle blades will be need to open more and dieseling will be hard to eliminate,..or if you have a snotty cam that idles at a higher idle speed, sometimes it's hard to eliminate dieseling.
Good luck!
Backfiring through the carb is likely a timing issue. If you've checked your timing and it appears to be set to specs, you may have a harmanic balancer with a spun outer ring giving you bad readings. Also, I'm assuming your plug wire are properly routed,..right?
For now, retard the initial timing until you eliminate the backfiring problem (turn the distributor clockwise).
The dieseling is likely caused by the throttle blades being open too much at idle. But if you retard your inital timing you'll have to open the TB's further to maintain your idle speed which will aggravate the dieseling prob.
So, I'd switch to manifold (full-time) vacuum (if not already) which will mean you'll need less of a throttle blade opening at idle. If this is q-jet carb, use the port on the passenger's side of the carb.
Also, if this is an old, tired engine with poor compression, your throttle blades will be need to open more and dieseling will be hard to eliminate,..or if you have a snotty cam that idles at a higher idle speed, sometimes it's hard to eliminate dieseling.
Good luck!
Last edited by 73, Dark Blue 454; Jul 11, 2006 at 02:48 PM.
Safety Car
Joined: May 2003
Posts: 3,814
Likes: 105
From: Dearborn Heights Michigan
Double check the plug wires and check #1 at TDC and recheck the wire order. I had a similar problem with my 70 L46 and it turned ot to be 2 plug wires switched. Worth a double check.
Fred
Fred
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Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
Originally Posted by 73, Dark Blue 454
If the distributor were 180 degrees off, the engine wouldn't run.
Backfiring through the carb is likely a timing issue. If you've checked your timing and it appears to be set to specs, you may have a harmanic balancer with a spun outer ring giving you bad readings. Also, I'm assuming your plug wire are properly routed,..right?
For now, retard the initial timing until you eliminate the backfiring problem (turn the distributor clockwise).
The dieseling is likely caused by the throttle blades being open too much at idle. But if you retard your inital timing you'll have to open the TB's further to maintain your idle speed which will aggravate the dieseling prob.
So, I'd switch to manifold (full-time) vacuum (if not already) which will mean you'll need less of a throttle blade opening at idle. If this is q-jet carb, use the port on the passenger's side of the carb.
Also, if this is an old, tired engine with poor compression, your throttle blades will be need to open more and dieseling will be hard to eliminate,..or if you have a snotty cam that idles at a higher idle speed, sometimes it's hard to eliminate dieseling.
Good luck!
Backfiring through the carb is likely a timing issue. If you've checked your timing and it appears to be set to specs, you may have a harmanic balancer with a spun outer ring giving you bad readings. Also, I'm assuming your plug wire are properly routed,..right?
For now, retard the initial timing until you eliminate the backfiring problem (turn the distributor clockwise).
The dieseling is likely caused by the throttle blades being open too much at idle. But if you retard your inital timing you'll have to open the TB's further to maintain your idle speed which will aggravate the dieseling prob.
So, I'd switch to manifold (full-time) vacuum (if not already) which will mean you'll need less of a throttle blade opening at idle. If this is q-jet carb, use the port on the passenger's side of the carb.
Also, if this is an old, tired engine with poor compression, your throttle blades will be need to open more and dieseling will be hard to eliminate,..or if you have a snotty cam that idles at a higher idle speed, sometimes it's hard to eliminate dieseling.
Good luck!
Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
The fuel pump is working fine and the wires are correctly (verified twice) installed. The carb backfires bad, often throwing flames up. i can only get up to about 40 mph on a flat road...and it takes a while
Drifting
Joined: Jan 2006
Posts: 1,832
Likes: 38
From: Cedar,BC
Pull off your rocker covers and look for an obvious pushrod or rocker arm problem,or even worse you may have lost a cam lobe or two.A compression and or leakdown test might be a good idea to help diagnose your problem.
Drifting
Joined: Jul 2002
Posts: 1,254
Likes: 1
From: Edinburgh
Originally Posted by kaymonster
It is 8 degrees.
Pro
Joined: Sep 2004
Posts: 595
Likes: 0
From: Boston MA
Originally Posted by kaymonster
It is 8 degrees.
Do you have an adjustable timing light?
Pull the vacuum advance off the carb.
Plug the vacuum port on the carb temporarily.
Check the timing at full advance.
It should be 36.
Thanks,
Joe
Burning Brakes
Joined: Jun 2005
Posts: 769
Likes: 0
From: NorCal 71 Lt-1
may i ask how was the car running before you replaced all the parts? how does she idle, shakes, misfires? are running points or electronic / hei? have you tried to advance the timing to see what she does?
Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
yes i have. It ran fine..... it had been garaged for 15 years when I aquired the car through a death in the family. it looked perfect but i had a mechainc friend do a full inspection and had things fixed/replaced (gas tank, plugs, distributor, cooling system flush, etc, etc,) so i could fire it up. it ran fine for about 300 miles. one day i tried to start it and it just had all of these symptoms. i expected problems, but i cant seem to find the source of this one
Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
yes i have. It ran fine..... it had been garaged for 15 years when I aquired the car through a death in the family. it looked perfect but i had a mechainc friend do a full inspection and had things fixed/replaced (gas tank, plugs, distributor, cooling system flush, etc, etc,) so i could fire it up. it ran fine for about 300 miles. one day i tried to start it and it just had all of these symptoms. i expected problems, but i cant seem to find the source of this one
Thread Starter
Intermediate
Joined: May 2006
Posts: 44
Likes: 0
From: Spring Valley California
yes i have. It ran fine..... it had been garaged for 15 years when I aquired the car through a death in the family. it looked perfect but i had a mechainc friend do a full inspection and had things fixed/replaced (gas tank, plugs, distributor, cooling system flush, etc, etc,) so i could fire it up. it ran fine for about 300 miles. one day i tried to start it and it just had all of these symptoms. i expected problems, but i cant seem to find the source of this one
Intermediate
Joined: Jun 2006
Posts: 31
Likes: 0
You can check the ignition timing by finding top dead center on the #1 cylinder, and checking the position of the distributor rotor. It should point in the direction of the #1 cylinder. To verify this, check the repair manual for your corvette year and engine. The firing order will be in there, so you verify what position the distributor rotor should be pointing when #1 cylinder is in top dead center.