Backfiring through carb
Thread Starter
Cruising
Joined: Apr 2008
Posts: 10
Likes: 0
From: Valparaiso Indiana
Backfiring through carb
I just did a head job on my 76' L-48 stock. I had to replace one the heads because the #6 intake valve sucked up into the valve seat.
So I just put everything back together and when I turn in over I get backfiring through the carb. I found TDC on #1 and turned the dist. 180 and still the same backfiring through the carb.
My questions are:
What could be causing this?
Could the valves be to tight?
Could the dist. be off a tooth or 2?
I adjusted the valves as stated in Chiltons.
I am up for any help possible.
Thanks.
So I just put everything back together and when I turn in over I get backfiring through the carb. I found TDC on #1 and turned the dist. 180 and still the same backfiring through the carb.
My questions are:
What could be causing this?
Could the valves be to tight?
Could the dist. be off a tooth or 2?
I adjusted the valves as stated in Chiltons.
I am up for any help possible.
Thanks.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Sometimes if you don't know where you went wrong it's best to take out the distributor, and start over.
First, unplug the IGN and take out the #1 spark plug. Hold your finger over the hole, and watch the balancer TDC mark on the timing tab. have someone bump the starter until you feel air pushing out from under your finger and have them stop when the TDC mark is at 0.
Then, pull the distributor. Make a mark on the housing under the cap, directly under where the #1 spark plug is.
With the vacuum can facing forward on the passenger side, and the shaft notches aligned, point the rotor to the last intake bolt to the back on the driver's side and drop the distributor in.
It might fall right in the first time, but you're wanting it to seat all the way, and still have the rotor pointing to the mark you made on the case.
If the balancer is at TDC mark is at the 0 on the timing tab, and the rotor is point to the mark, then you have it in right. It may take a few stabs. Make sure the hold down is back on and tightened enough to hold it but still loose enough to be turned for adjustment.
Now, while it's still at TDC #1, loosen all the rocker nuts. In the following order, tighten them till you're at zero lash, and then follow it with a 1/2 turn on that nut.
Exhaust Valve Rockers: 1 - 3 - 4 - 8
Intake Valve Rockers: 1 - 2 - 5 - 7
Now, put your finger back on the #1 plug bore, and have someone bump it around to TDC one full revolution from where it was. This will be TDC #6. With the timing mark at 0 adjust the following rocker nuts the same as above.
Exhaust Valve Rockers: 2 - 5 - 6 - 7
Intake Valve Rockers: 3 - 4 - 6 - 8
So long as you stopped when you hit zero lash, and went one 1/2 turn further, then your rockers are adjusted.
Now is when you can button everything back up, start it, and time it.
First, unplug the IGN and take out the #1 spark plug. Hold your finger over the hole, and watch the balancer TDC mark on the timing tab. have someone bump the starter until you feel air pushing out from under your finger and have them stop when the TDC mark is at 0.
Then, pull the distributor. Make a mark on the housing under the cap, directly under where the #1 spark plug is.
With the vacuum can facing forward on the passenger side, and the shaft notches aligned, point the rotor to the last intake bolt to the back on the driver's side and drop the distributor in.
It might fall right in the first time, but you're wanting it to seat all the way, and still have the rotor pointing to the mark you made on the case.
If the balancer is at TDC mark is at the 0 on the timing tab, and the rotor is point to the mark, then you have it in right. It may take a few stabs. Make sure the hold down is back on and tightened enough to hold it but still loose enough to be turned for adjustment.
Now, while it's still at TDC #1, loosen all the rocker nuts. In the following order, tighten them till you're at zero lash, and then follow it with a 1/2 turn on that nut.
Exhaust Valve Rockers: 1 - 3 - 4 - 8
Intake Valve Rockers: 1 - 2 - 5 - 7
Now, put your finger back on the #1 plug bore, and have someone bump it around to TDC one full revolution from where it was. This will be TDC #6. With the timing mark at 0 adjust the following rocker nuts the same as above.
Exhaust Valve Rockers: 2 - 5 - 6 - 7
Intake Valve Rockers: 3 - 4 - 6 - 8
So long as you stopped when you hit zero lash, and went one 1/2 turn further, then your rockers are adjusted.
Now is when you can button everything back up, start it, and time it.
Instructor
Joined: Mar 2005
Posts: 104
Likes: 0
From: Perkasie PA
Your timing is still off. Lots of people have their method and every one should work. Here is what I would do:
1) Take of the drivers side valve cover.
2) Pull the coil wire out of the top of the distributor so the car will not start
3) Have someone (or long arms) tap the igntion key to slowly crank the engine around. Watch the intake valve of the number one cylinder (cylinder farthest forward on driver side, valve is second in from end). Once this valve has opened (gone down) start looking at the harmonic balance
4) While your partner taps the key watch for the timing mark to come around to the timing tab. Once it gets to around 10 degrees stop tapping. If you miss you need to go all the way around twice to get back here. If you are close use a breaker bar and socket on the balance pulley to hand crank the engine.
5) Put a little tape on the base of the distributor where the number one spark plugs wire is and put a line on it. Take the cap off. The rotor should be pointing to where #1 spark plug wire was according to your tape line. My guess is it is pointing back toward the firewall not toward the front of the engine where your mark is.
If it is pointing to the back remove the distributor and rotate it 180 degrees or so to get it back up front. It may not drop back in all the way. If not you need a long thin screw driver to move the oil pump tang waaaay down in the bottom of the distributor hole. Point it to #5 exhaust then it should drop in.
If it is pointing close to your location it is just off "a tooth" as some say. It may be pointing to the next post over. You can solve this by moving all the wires around one post to line up #1 on the cap with the position of the actual rotor.
If it is very close then it should start and have more or less timing than 10 degrees in which case you may have something else wrong but unlikely. Over tight valve will make it idle and run aweful but it should not back fire unless you tightened them like they were solid lifters.
Durango and I submitted at the same time....
1) Take of the drivers side valve cover.
2) Pull the coil wire out of the top of the distributor so the car will not start
3) Have someone (or long arms) tap the igntion key to slowly crank the engine around. Watch the intake valve of the number one cylinder (cylinder farthest forward on driver side, valve is second in from end). Once this valve has opened (gone down) start looking at the harmonic balance
4) While your partner taps the key watch for the timing mark to come around to the timing tab. Once it gets to around 10 degrees stop tapping. If you miss you need to go all the way around twice to get back here. If you are close use a breaker bar and socket on the balance pulley to hand crank the engine.
5) Put a little tape on the base of the distributor where the number one spark plugs wire is and put a line on it. Take the cap off. The rotor should be pointing to where #1 spark plug wire was according to your tape line. My guess is it is pointing back toward the firewall not toward the front of the engine where your mark is.
If it is pointing to the back remove the distributor and rotate it 180 degrees or so to get it back up front. It may not drop back in all the way. If not you need a long thin screw driver to move the oil pump tang waaaay down in the bottom of the distributor hole. Point it to #5 exhaust then it should drop in.
If it is pointing close to your location it is just off "a tooth" as some say. It may be pointing to the next post over. You can solve this by moving all the wires around one post to line up #1 on the cap with the position of the actual rotor.
If it is very close then it should start and have more or less timing than 10 degrees in which case you may have something else wrong but unlikely. Over tight valve will make it idle and run aweful but it should not back fire unless you tightened them like they were solid lifters.
Durango and I submitted at the same time....
Racer
Joined: Sep 2007
Posts: 382
Likes: 0
From: CT
Your timing is still off. Lots of people have their method and every one should work. Here is what I would do:
1) Take of the drivers side valve cover.
2) Pull the coil wire out of the top of the distributor so the car will not start
3) Have someone (or long arms) tap the igntion key to slowly crank the engine around. Watch the intake valve of the number one cylinder (cylinder farthest forward on driver side, valve is second in from end). Once this valve has opened (gone down) start looking at the harmonic balance
4) While your partner taps the key watch for the timing mark to come around to the timing tab. Once it gets to around 10 degrees stop tapping. If you miss you need to go all the way around twice to get back here. If you are close use a breaker bar and socket on the balance pulley to hand crank the engine.
not something i'd recommend. crank pulley bolt is only ~ 60# ft
5) Put a little tape on the base of the distributor where the number one spark plugs wire is and put a line on it. Take the cap off. The rotor should be pointing to where #1 spark plug wire was according to your tape line. My guess is it is pointing back toward the firewall not toward the front of the engine where your mark is.
If it is pointing to the back remove the distributor and rotate it 180 degrees or so to get it back up front. It may not drop back in all the way. If not you need a long thin screw driver to move the oil pump tang waaaay down in the bottom of the distributor hole. Point it to #5 exhaust then it should drop in.
If it is pointing close to your location it is just off "a tooth" as some say. It may be pointing to the next post over. You can solve this by moving all the wires around one post to line up #1 on the cap with the position of the actual rotor.
you can walk the rotor around too. basically i drop the distributor in in the orientation i want and let the rotor aim where it needs to drop in. then if you pull the distributor up ~1/2" you can turn the rotor clockwise about 5-10 degrees. drop distributor back down and rotor will point at next position
If it is very close then it should start and have more or less timing than 10 degrees in which case you may have something else wrong but unlikely. Over tight valve will make it idle and run aweful but it should not back fire unless you tightened them like they were solid lifters.
Durango and I submitted at the same time....
1) Take of the drivers side valve cover.
2) Pull the coil wire out of the top of the distributor so the car will not start
3) Have someone (or long arms) tap the igntion key to slowly crank the engine around. Watch the intake valve of the number one cylinder (cylinder farthest forward on driver side, valve is second in from end). Once this valve has opened (gone down) start looking at the harmonic balance
4) While your partner taps the key watch for the timing mark to come around to the timing tab. Once it gets to around 10 degrees stop tapping. If you miss you need to go all the way around twice to get back here. If you are close use a breaker bar and socket on the balance pulley to hand crank the engine.
not something i'd recommend. crank pulley bolt is only ~ 60# ft
5) Put a little tape on the base of the distributor where the number one spark plugs wire is and put a line on it. Take the cap off. The rotor should be pointing to where #1 spark plug wire was according to your tape line. My guess is it is pointing back toward the firewall not toward the front of the engine where your mark is.
If it is pointing to the back remove the distributor and rotate it 180 degrees or so to get it back up front. It may not drop back in all the way. If not you need a long thin screw driver to move the oil pump tang waaaay down in the bottom of the distributor hole. Point it to #5 exhaust then it should drop in.
If it is pointing close to your location it is just off "a tooth" as some say. It may be pointing to the next post over. You can solve this by moving all the wires around one post to line up #1 on the cap with the position of the actual rotor.
you can walk the rotor around too. basically i drop the distributor in in the orientation i want and let the rotor aim where it needs to drop in. then if you pull the distributor up ~1/2" you can turn the rotor clockwise about 5-10 degrees. drop distributor back down and rotor will point at next position
If it is very close then it should start and have more or less timing than 10 degrees in which case you may have something else wrong but unlikely. Over tight valve will make it idle and run aweful but it should not back fire unless you tightened them like they were solid lifters.
Durango and I submitted at the same time....
