The thing that gets me is he stated it sometimes spits fire from the carb. I am no expert but doesn't a valve usually have to be open for that to happen. Which to me would mean incorrect valve adjustment or timing issue, weather it be electronic or mechanical. As I stated, I am no expert and please correct me if I am wrong.
Backfiring out carb and wont run right
- Thread starter davalf
- Start date
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65Val
Average Length Member
I mentioned that up there a ways...^^^^^^
davalf
Active Member
Unfortunately no. I thought about that so we can eliminate something.
Stock non-adjustable.
Changed the fuel pump and the problem persists.
Ok time to come clean. I have a basic working knowledge of the mechanicals of a motor but this is by far the most I have done, meaning my first rebuild. My neighbor, who has a lot of experience, has helped me along the whole way. He has been an on and off mechanic as a job for 30+ years so I tend to trust where he has guided me.
We went out there this morning and talked about what it could be. I mentioned the timing chain being off by a tooth and he said know being he is the one who put it on. I mentioned the vacuum leak and he explained to me that we eliminated that by when he covered the carb with it running, it died down rather than rev up. I don't know if that is how it works because I am still learning. :sign3:
We have been constantly adjusting the timing because the car keeps changing the way it runs.
We did discover, if you slowly move the throttle, no fuel comes out for the first 1/8th of travel or so. If you move it quickly you get fuel. I am guessing that could be the float level or accel pump?
The plan: By next weekend, we are going to change the condenser and points to eliminate that. We are going to check the voltage at the coil to make sure it is getting what it needs. Attach a fuel pressure gauge to make sure we are getting the fuel we need. If that doesn't solve it, then I will contact national carbs and ask them if they want me to dive into the carb or if they will send a new one.
The video, I had a lot of trouble getting the motor to fire. I had to advance the timing a little to get it to start. Before this vid, on one start, I had a 3 foot flame shoot out the carb. Scary. I have to do what I did in this vid a few times until it warms up, then it will idle, once I out it into gear, and give some throttle, it dies down unless I give quick short bursts of throttle. Hopefully my explanations are clear and the video helps. Sorry for the lengthy post.
ops:[ame="https://www.youtube.com/watch?v=Rrcd-MB0cd4"]360 run probs - YouTube[/ame]
No one wants to consider this but a back fire thru the carb can also mean-----------here it comes------wiped out cam lobe!
67Dart273
Well-Known Member
Get down to basics
TIMING. Set this and forget it. Wrench the engine around with the timing mark about 10 BTC or a bit more. Loosen the dist. clamp, rotate the dist CW (retard) and put a meter or test lamp on the points (coil NEG terminal). With key in "run" SLOWLY rotate distributor "advanced" (CCW) until the lamp lights or you get voltage on the meter. Snug down the distributor
ESTIMATE whether the advance works. Do this by "springing" the rotor CW. It should spring right back. This is the spring / weight mechanism of the mechanical advance.
COMPRESSION. Run a compression check, and if you can borrow or afford one, a leak down check. Horrid Freight sells leak down testers for 40 bucks
PLUGS. Check the plugs for fowling, and for cracks.
WIRES. Check the plug wires with an ohmeter. It depends on the type of wire, but if they are resistance radio suppressor wires, they will have some resistance. No wire should be greatly different than the rest. Take them one at a time, hook to your meter, and "shake" them. This should show up bad spots in the wires.
AN OPEN PLUG WIRE CAN CAUSE THIS
FIRING ORDER. Make ABSOLUTELY certain you have the firing order correct. It's VERY easy to switch 5 and 7. We have all done it, all of us.
========================================
THEN
========================================
Examine the cam........pull the covers, crank, and examine the valves for "all they all" opening and closing
cam TIMING. You can easily estimate cam timing, read your shop manual...........there's a procecure in there to do that.............
Download a factory shop manual, free, right here.........
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
TIMING. Set this and forget it. Wrench the engine around with the timing mark about 10 BTC or a bit more. Loosen the dist. clamp, rotate the dist CW (retard) and put a meter or test lamp on the points (coil NEG terminal). With key in "run" SLOWLY rotate distributor "advanced" (CCW) until the lamp lights or you get voltage on the meter. Snug down the distributor
ESTIMATE whether the advance works. Do this by "springing" the rotor CW. It should spring right back. This is the spring / weight mechanism of the mechanical advance.
COMPRESSION. Run a compression check, and if you can borrow or afford one, a leak down check. Horrid Freight sells leak down testers for 40 bucks
PLUGS. Check the plugs for fowling, and for cracks.
WIRES. Check the plug wires with an ohmeter. It depends on the type of wire, but if they are resistance radio suppressor wires, they will have some resistance. No wire should be greatly different than the rest. Take them one at a time, hook to your meter, and "shake" them. This should show up bad spots in the wires.
AN OPEN PLUG WIRE CAN CAUSE THIS
FIRING ORDER. Make ABSOLUTELY certain you have the firing order correct. It's VERY easy to switch 5 and 7. We have all done it, all of us.
========================================
THEN
========================================
Examine the cam........pull the covers, crank, and examine the valves for "all they all" opening and closing
cam TIMING. You can easily estimate cam timing, read your shop manual...........there's a procecure in there to do that.............
Download a factory shop manual, free, right here.........
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
Blue Grey Duster
Well-Known Member
I'm Hooked !
Can't wait for the results.
Can't wait for the results.
russhal
Well-Known Member
I had problems with a slant 6 with rough idle. It didn't spit fire through the carb but was a fuel delivery problem. Had a fitting sucking air. When I fixed that, it ran fine. You could have more than one problem. Need a friend with a spare carb. Check the fuel line from tank to carb. Could be a counter weight in the distributer sticking.
Woods74
Broke Senior
Gonna toss this out there, distributor 180 degrees out. :blob:
Ok, now for the "come clean"...
I agree with Del, to do a compression check next. Make sure that you have good compression and that the cylinders are close in compression.
This neighbor who is a "mechanic on and off"...
Not knocking the guy, but the distributor drive gear can be a little tricky for new "mopar" builders. If he is not familiar with SB mopars, the distributor drive gear slot may not point to #1 cylinder when it is at TDC. This is very easy to fix.
1. Make sure that you know where your TDC is. A dead stop tool is the best way to find it.
2. Once you know for sure where TDC is, then put the engine at TDC and remove the distributor cap. Where is the rotor pointing? Make this the #1 spark plug wire location for the distributor cap. Then follow the firing order around the distributor cap in the direction that the rotor spins 1-8-4-3-6-5-7-2.
3. Then manually put the engine at 10° BTDC with the marks on the damper and turn the distributor so that the rotor points at/has contact with the #1 wire position on the distributor cap.
4. Try to start it and adjust the timing from there. You should go for 34° - 36° total advance at 2000 - 2500 RPM.
Positioning the distributor gear is difficult for some beginners to the SB Mopar.
And yes, make sure that you are on the compression stroke when the distributor is at #1, or you may be 180° off as stated above. That is easy to fix by just loosening the distributor and spinning the rotor 180°.
Also a key rule:
If it backfires through the exhaust, you may be too far advanced on your timing.
If it backfires through the carb, then you may be too far retarded on your timing.
I agree with Del, to do a compression check next. Make sure that you have good compression and that the cylinders are close in compression.
This neighbor who is a "mechanic on and off"...
Not knocking the guy, but the distributor drive gear can be a little tricky for new "mopar" builders. If he is not familiar with SB mopars, the distributor drive gear slot may not point to #1 cylinder when it is at TDC. This is very easy to fix.
1. Make sure that you know where your TDC is. A dead stop tool is the best way to find it.
2. Once you know for sure where TDC is, then put the engine at TDC and remove the distributor cap. Where is the rotor pointing? Make this the #1 spark plug wire location for the distributor cap. Then follow the firing order around the distributor cap in the direction that the rotor spins 1-8-4-3-6-5-7-2.
3. Then manually put the engine at 10° BTDC with the marks on the damper and turn the distributor so that the rotor points at/has contact with the #1 wire position on the distributor cap.
4. Try to start it and adjust the timing from there. You should go for 34° - 36° total advance at 2000 - 2500 RPM.
Positioning the distributor gear is difficult for some beginners to the SB Mopar.
And yes, make sure that you are on the compression stroke when the distributor is at #1, or you may be 180° off as stated above. That is easy to fix by just loosening the distributor and spinning the rotor 180°.
Also a key rule:
If it backfires through the exhaust, you may be too far advanced on your timing.
If it backfires through the carb, then you may be too far retarded on your timing.
davalf
Active Member
Thank you all for the input. I have a lot of things to try and solve this problem. Unfortunately, I have to go to work, in LA, for 5 days and I will be back this weekend. I am hoping to fix it then so I can move onto body and paint.
Inertia
Well-Known Member
It won't run 180* out.. it'll flame, cough and fart a whole bunch,, but it won't RUN..
Think about it.. 180* out means the valves on that cylinder are in overlap,, both open in most cases.. The piston has just come up pushing out the exhaust,, and the intake valve is just opening to take a charge of fuel... there is no compression..
hope it helps..
Lonewolf3165
Living the Dream!
Krazy, I thinks you got your keys mixed up.:wink:
I think you meant to say; Backfires through exhaust= ignition timing is too retarded.
Backfires through intake= too far advanced ignition timing.
To the Op: Non adjustable factory rockers doesn't necessarily mean the valves can't be too tight. I would still recommend you verify they are good. Especially if there was a valve job done or pushrods & lifters replaced.
I think you meant to say; Backfires through exhaust= ignition timing is too retarded.
Backfires through intake= too far advanced ignition timing.
To the Op: Non adjustable factory rockers doesn't necessarily mean the valves can't be too tight. I would still recommend you verify they are good. Especially if there was a valve job done or pushrods & lifters replaced.
davalf
Active Member
Ok a quick update. Thanks again to all who have posted some ideas.
I didn't get a chance to mess with it as much as I would have liked to but I did a little. I got a fuel pressure gauge and I am running 6-8lbs. So that takes care of that.
Like I said earlier, if you slowly move the throttle, you do not get any fuel coming out the accel. pump nozzles. Only if you give it a quick burst. So I pulled the top off the carb and checked to see if the accel. pump had any issues. It looked fine so I blew some air into the fuel passage from the accel. pump and it seemed clear. Put it all back together and same issue of no fuel. So I ordered a new accel. pump.
As for the way the car runs, it didn't really have the backfiring issue. It struggled to stay running until it warmed up, and then the idle was high. I didn't mess with the timing or dive any deeper then that. Another week of work and then I will be back problem solving.
Oh, and we put a different condenser in it to rule that out, and we did. Same problem. But for whatever reason, it doesn't seem as bad.
I didn't get a chance to mess with it as much as I would have liked to but I did a little. I got a fuel pressure gauge and I am running 6-8lbs. So that takes care of that.
Like I said earlier, if you slowly move the throttle, you do not get any fuel coming out the accel. pump nozzles. Only if you give it a quick burst. So I pulled the top off the carb and checked to see if the accel. pump had any issues. It looked fine so I blew some air into the fuel passage from the accel. pump and it seemed clear. Put it all back together and same issue of no fuel. So I ordered a new accel. pump.
As for the way the car runs, it didn't really have the backfiring issue. It struggled to stay running until it warmed up, and then the idle was high. I didn't mess with the timing or dive any deeper then that. Another week of work and then I will be back problem solving.
Oh, and we put a different condenser in it to rule that out, and we did. Same problem. But for whatever reason, it doesn't seem as bad.
No sir. You have it backwards.
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