360 dying at idle???

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Chained_360

Chained_360

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Indianapolis, IN
Alright, so my '68 notch has more problems than I initially accepted. After a still unsolved escapade here: Running rich/stumbling after replacing spark plugs
the problem has now gotten worse. Starting yesterday, the car would refuse to idle. It's a slightly warmed over 360 that I didn't build, I've only put a new carb, cap, rotor, plugs, and wires on it (fuel and now vacuum line too). It was strange because yesterday morning (7:20), I started it right up to go take my SAT. It was a sunny and decently warm day for Alaska, and the car warmed up fine. It then started to do what it's been doing for the past few weeks. Every time, on the first drive of the day, for the first couple minutes of driving, it would have trouble idling. When cruising, it ran fine, but for the first few minutes again, if I tried to give it gas, it would stumble a little. It never died, but sometimes it would backfire. After a couple minutes of driving, the problem would go away and it would idle fine, I could drop a gear and punch it no problem. And it only would do that on the first drive of the day.

That was happening for the whole past week. Then yesterday, after driving the car home from my SAT (again fine), and gave my dad's buddy a ride in the thing. The car drove perfectly fine, and of course, it would get right down to business when I got on the throttle. The car sat for about two hours before I had to drive it again, and when I started it, it fired up and then died. I kept firing it up, and it would keep running so long as I kept my foot on the gas. As soon as I let up, the car would die again. Looking under the hood, I saw that the old vacuum PCV line was falling apart. I threw some new line on quite a while later in the day, started it up, and it ran fine.

Then this morning, again, the car started up and warmed up normally despite the rain, and then on the way to work it was doing the exact same thing it normally does on the first drive of the day. After a few minutes, the car was driving normally and idling fine, until it stalled at a stoplight. After some difficulty, I got it fired back up, and into a parking lot, where it absolutely refused to run at idle. I would give it gas and it would backfire and cough and sputter, and then die if I tried to put it into gear.

I don't really exactly know where to start. I have to get the car home before I can start looking at it. In the thread I linked to, it was discussed that the car was running rich and possible had a bad power valve, which wouldn't surprise me. Despite it having a brand new holley 650 4 barrel (vacuum secondaries, electric choke) with PV blowout protection., it's suffered some nasty backfires out the carburetor. You can imagine the look on my face when I pulled the plugs out saturday to see that it was running leaner than an anorexic supermodel (slight exaggeration). I thought it may have been a vacuum leak, but I replaced all of the vacuum line in the car later in the evening.

Apologies for the wall of text, I'm just very puzzled. Any help is greatly appreciated.
 
If you're sure of the firing order, and the timing, check the rotor. A friend of mine was having alot of issues, and was sure it was his new carb. It turns out when someone put the distributor cap on, they caught the metal contact on the rotor, bending it so it didn't line up with the distributor cap contact. I would take anything I could out of the situation, like the pcv, an vacuum advance, and any other vacuum lines. Go back, and check the basics, then maybe a different coil. Look in the carb when running, and when it's stopped. You shouldn't have any fuel wetting the inside of the carb,or intake.
 
furyus2 said:
If you're sure of the firing order, and the timing, check the rotor. A friend of mine was having alot of issues, and was sure it was his new carb. It turns out when someone put the distributor cap on, they caught the metal contact on the rotor, bending it so it didn't line up with the distributor cap contact. I would take anything I could out of the situation, like the pcv, an vacuum advance, and any other vacuum lines. Go back, and check the basics, then maybe a different coil. Look in the carb when running, and when it's stopped. You shouldn't have any fuel wetting the inside of the carb,or intake.
Click to expand...
I'm sure of the firing order, and the rotor is new too. I'm not so confident in the timing. I can't check it right now, and I'm not that great with it to begin with. It hasn't been checked in a long while
 
I had this exact problem last week. Look for " fuel problem thread" on 67 Dart.

I had one of my linkages in the wrong place. The pics are on the thread. Anyway, I could not get it to idle for anything. There were theee places that were spaced just millimeters apart. Moved it to the lowest point, and boom, it started purring like a kitten. Who woulda thunk?

I bet I did the timing thing three or four times, removed the timing cover to make sure it did not slip, adjusted the carb countless times. All to no avail.

Not sure this will help, but I hope you work it out
 
Thanks, I took a look through your thread, but my throttle linkage isn't that style. It may/may not be a little more jerry-rigged (piece of 1/2 flatbar steel with a couple a holes drilled in it :rolleyes:), but it ran fine just last week. I don't think it would be a linkage issue, but I'll double check when I get the car home.
 
Points ignition= replace the condenser inside the distributor.

Also do this.
Count the turns it takes to bottom the idle metering screws and then pull them out.
Shoot a shot of WD40 in the holes they came out of and give them each a blast of compressed air.
Put the idle screws back in all the way and back them out the turns they were.
 
What are the chances your fuel is contaminated with water?
Then the entire slow-speed circuit will be lean,every time It is asked to work. Then after first start, the water gets sucked up and it is fine.
The same could be happening with a very low fuel-level in the bowl. Pull-over gets harder and harder. This is particularly troublesome on a cold engine, as at this time the AFR needs to be rich. I would go here first. I would check the fuel-pump output over 30 seconds and compare it to the spec. At this time you can also check for water, just route the pump output into a clear mason-jar.
But I don't think this is a pump issue, strictly a low-speed circuit and possibly the choke coming off too early as well.
 
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Pretty low chances of contamination. I just filled it to the brim on friday. It was running fine then, and was sunny the whole weekend. I did raise the float just a little bit, but still the same thing
AJ/FormS said:
What are the chances your fuel is contaminated with water?
Then the entire slow-speed circuit will be lean,every time It is asked to work. Then after first start, the water gets sucked up and it is fine.
The same could be happening with a very low fuel-level in the bowl. Pull-over gets harder and harder. This is particularly troublesome on a cold engine, as at this time the AFR needs to be rich. I would go here first. I would check the fuel-pump output over 30 seconds and compare it to the spec. At this time you can also check for water, just route the pump output into a clear mason-jar.
Click to expand...
 
Chained_360 said:
Pretty low chances of contamination. I just filled it to the brim on friday. It was running fine then, and was sunny the whole weekend. I did raise the float just a little bit, but still the same thing
Click to expand...
In that case, I would remove the front metering block, strip it down and soak in carb-cleaner. In the morning a good soap and water washing and blow out the low-speed circuit. Then blow some brake cleaner through every circuit to prove none have a problem.
But if your ignition timing is too far advanced it is easily possible that you have slammed the throttles shut on the curb-idle screw, and now the low-speed circuit is more or less shut off by that smooth move.

So here's a possible cure; screw the curb idle screw in one complete turn.Then if the idle-speed is too high, just grab the dizzy and push it towards the firewall until the speed seems right to you. Finally, adjust the mixture screws for best idle, then crank them back out(more fuel), 1/4 turn. Try it and see. If it works, then we have some tuning to do.
 
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Alright, I finally got around to messing with the car again. I took apart the primary side of the carb and looked at it. I didn't clean it out because everything was very shiny and no visible gunk was there. I also replaced the power valve with an identical one I had laying around. I checked the fuel pump and it checked out okay, I got blasted in the hand with a nice, solid jet of gas.

So I pushed the idle screw all the way in and fired it up, let it run for a bit, and then started to back the idle screw down until it stalled. I got it idling at around 1000 RPM, maybe 900, but the motor wasn't too happy. Lots of small chuffs and pops out the tailpipes, sooty-smelling exhaust, and the motor was noticeably shaking. I tried putting it into gear a couple times, and every time it would cause the engine to stall.

I hooked up a timing light to check the timing, and then realized how big of a pain in the *** I was in for. I have a 360 with a pre 73(?) water pump (whenever they switched the coolant return side), but the timing mark is still on the driver's side of the motor. Basically, the radiator return hose blocks the degree marks on the block (which are almost illegible anyway), and so I can't adjust the timing. This next weekend I'll go ahead and fix that, but if y'all have any other tips that would help too. I don't know why the timing would have changed, I never messed with the ignition system prior to the current problem.

The next thing I'll do is check for vacuum leaks elsewhere in the motor using a paint can smoker. Again, the engine runs fine with some throttle, but dies below ~900-1000 RPM at idle.
 
Here's the degree mark plate

20170610_182955.jpg
 
I tell you what, just loosen the dist, and crank some advance into it, til the idle smooths out. Disable the VA. Adjust the mixture screws to 3/4 turn out on Holley types and 2 turns out on all others.then back out the curb idle screw, until the idle approaches 850. the pull in some more timing, then crank out the curb idle screw until the idle approaches 750 for cams smaller than 233*@.050, or 800 for cams smaller than 243, and 850 for cams smaller than 253.
Now, pull in a little more timing. if she smooths out pill in a little more. But if not, then put the timing back a bit.
At this point your T-port sync is getting close to where it needs to be.
So begin to cover the carb with a rag, starting with the secondaries. If the rpm goes up close the secondaries up tight.If the rpm goes down,she wants more bypass air in the front. Get that sorted, then re-index your balancer. After that is done, you can begin to work on your power-timing. Until that is sorted do not run WOT, and listen carefully for detonation. There is no telling where your power timing has ended up with all the distributor twisting I promoted.
Secure the D,hook the VA back up, and go for an easy cruise.
 
AJ, I followed you about halfway through your post before you lost me:D. I tried tweaking the dizzy a little bit, but it didn't seem to do much. I did raise the idle and then lower it to a point where it ran semi-smoothly, the engine wasn't shaking so bad and there weren't any big backfires. It kept chuffing though, like not pops, but small little chuffs out the tailpipes. I really don't know what the hell I'm doing here, I;ve never done any sort of tuning before on a carb/distributor setup before. I'm gonna see if anyone at the local hotrod club can help me out. I would take the car to work and have my boss help me out, but of course the issue is that it stalls when I put it in gear :(

I did check a couple other things, small things that seem more likely to fail in a matter of two hours of the engine being off. I replaced the PCV valve (needed it anyways), but no change in the way the engine ran. I checked the coil resistances, and they checked out (although the primary resistance was about 0.5 ohms above spec). I checked the ballast resistor as well, and it was about 1 ohm over spec as well. I tried bridging it, but again nothing changed with the way the motor ran. These issues are probably unrelated, but I'm kind of taking swings in the dark here. Any other things I should try? Sorry if I'm being dense :p
 
I tell you what, if advancing the idle-timing did little or nothing, then I would suspect the cam-timing is off. I would do a compression test to start with. It won't tell you if the cam timing is off, but it will indicate what direction to move in, and it may help to determine if the valves are closing.
 
So, as it turns out, apparently Holley installs a 3/8 vacuum port BEHIND the carburetor, facing the firewall...

I'm kicking myself so hard right now... I only noticed that the plug was blown off because I was in the middle of doing a compression test... Man, I feel so stupid.

519283300.jpg
 
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