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Discussion Starter · #1 ·
I'm trying to get my dad's d350 chasis truck w/flatbed running good. I have rebuilt the trash carb it has (carter AFB performance series), made sure all the vac lines are hooked up and in good condition, new fuel filter, and it even has an electric fuel pump to help out. I wanted to check the timing, but I can't see the timing marks on the balancer because the smog pump is in the way. I have no idea other than to try and set the timing by ear, but haven't tried this ever before, I've always used timing lights..

Anyone have any suggestions? This thing runs jam up until it warms up, and even then it only really acts up when you try pulling a hill...
 

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I usually just run and listen. Advance the ignition til it rattles while lugging, then dial the distributor back enough to stop the rattles. You may need to go a step richer on the metering rods now that all gas has alcohol. What exactly do you mean by "acts up"?
 

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Discussion Starter · #3 ·
Idles rough, dies out when you put it in gear, when you pull a hill it will sputter, hesitate and eventually die, we spent almost 2 hours the other night on a hill waiting for it to cool off so it would pull the rest of the hill without problems. After that happened I had my dad go and get an intake tube from the air filter to the fender air funnel to try and help the carb stay a little cooler, but that hasn't seemed to help as much as I was hoping.

On a side note, I know that this motor can have problems with vibration related to the torque converter, and was wondering if anyone has had the same problem and what the fix was?
 

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Yeah, sounds like a fuel issue. Ditto on the choke, but beyond that, it sounds like vapor lock. you referred to the "trash" carb as an AFB, that means it's not the original, so even rebuilt, there could be problems with it from sheer age if nothing else. The AFB is aluminum, and your average 360 isn't gonna generate enough heat to cause problems, but the fuel line near the engine could be an issue. This really shouldn't be an issue either since the fuel return line was introduced to alleviate this problem. Is the fuel return still plumbed in? If it is, a quick fix would be wrapping the line in a couple wraps with aluminum foil. If that solves it, you can work out re-routing for a permenant solution. Could be fuel delivery, maybe the pump is getting tired. Electric fuel pump to help out? Are you saying there's an electric pump in tandem with a mechanical pump or just an electric pump. I know the mid-80's was a crossover period for going to electrics, but not sure just when it was on every model before fuel injection. The electric pump could be possibly flooding the carb. Check fuel pressure.
Only vibration issue I've ever heard of related to the 360 is when using a zero-balance (318) converter. The lack of the external balance weight (needed by the 360) causes a vibration.
 

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Discussion Starter · #6 ·
Yeah, sounds like a fuel issue. Ditto on the choke, but beyond that, it sounds like vapor lock. you referred to the "trash" carb as an AFB, that means it's not the original, so even rebuilt, there could be problems with it from sheer age if nothing else. The AFB is aluminum, and your average 360 isn't gonna generate enough heat to cause problems, but the fuel line near the engine could be an issue. This really shouldn't be an issue either since the fuel return line was introduced to alleviate this problem. Is the fuel return still plumbed in? If it is, a quick fix would be wrapping the line in a couple wraps with aluminum foil. If that solves it, you can work out re-routing for a permenant solution. Could be fuel delivery, maybe the pump is getting tired. Electric fuel pump to help out? Are you saying there's an electric pump in tandem with a mechanical pump or just an electric pump. I know the mid-80's was a crossover period for going to electrics, but not sure just when it was on every model before fuel injection. The electric pump could be possibly flooding the carb. Check fuel pressure.
Only vibration issue I've ever heard of related to the 360 is when using a zero-balance (318) converter. The lack of the external balance weight (needed by the 360) causes a vibration.

All vacuum lines and return lines related to the fuel delivery and vapor system are hooked up and have helped with performance slightly. The afb has a manufacture date of 10/95. And I live in an area of arizona where the nominal summer temp is mid 90's, so things definitely get hot under that hood.. There is an electric fuel pump assisting the mechanical, under the assumption that the extended wheelbase could be a little more than the mechanical pump could handle (we didn't put the electric pump on it, it came that way from the school district my grandfather bought it from).

We manage mobile home rentals so this truck is essentially perfect for my dad as it has the room to carry all his tools, materials, air compressor, generator, etc. But we don't have the budget to be replacing the carb or anything huge like that, so I'm trying every simple, and essentially cost free ways to get this beast running better.

Oh and as far as the choke goes, it does stick, but after rebuilding the carb and fixing a few vacuum lines, it doesn't seem to be misbehaving, could it be terribly out of adjustment since it has an electric choke?
 

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i have heard running a mechanical and electric fuel pump can cause issues. you pretty much have to choose one or the other and go with it.

did you possibly find any black stuff in the carb when you rebuilt it?
 

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Discussion Starter · #8 ·
i have heard running a mechanical and electric fuel pump can cause issues. you pretty much have to choose one or the other and go with it.

did you possibly find any black stuff in the carb when you rebuilt it?
Nothing more than your average filth of a carburetor. I did however remove quite a bit of sand from the float chambers... Could have come from the fact that grass is a rarity here in Kingman.. I will have to get ahold of a cover plate to remove the mechanical pump. Maybe I'll also pick up an in line fuel pressure gauge
 

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I'd definitely make sure that fuel return line is hooked up (return back to the fuel tank). The mechanical pump will serve as an effective pressure limiter to the electric pump, so it's probably not flooding from excess volume, unless the fuel return line is capped and the fuel has nowhere to go. Possible the idle speed screw bleeds could be fouled. Start at a high idle. There are 2 screws on the front lower section of the carb. Gently flush them down, then unscrew 1.5 complete turns. Start up, get up a high idle around 1500rpm, then take one screw and slowly screw in 1/2 turn. Engine rpm should vary slightly. Then return to original spot. Now unscrew another 1/2 turn, meaning 2 total turns. Better or worse? Leave it where it's best and repeat with the other screw. What you are looking for is where rpm will rise to highest point in response to adjustment. If one or both are bad, you can screw in or out and it'll basically make no difference. One might work, and the other is like being a dumb post, totally useless. If that happens, you have a problem. Could be internal damage, or possibly just crud. If you see improvement, take a test drive on the new settings. I'm thinking you do have a fuel delivery issue. The electric could be failing and needs time to cool off as you indicated earlier. The tandem pump thing was used, usually to help maintain good fuel supply (and combat vapor locking fuel lines), not that it was needed with a healthy factory system. Sounds like they were having issues when they added that. Hate to say it but unless you can verify adequate fuel supply, I'd scrag both pumps for new ones, mechanical first, then electric if needed. I would test a new mechanical with the electric removed and the line spliced, otherwise the possibly dead electric could restrict flow. I'm in South Mississippi. We know hot weather too. Only time I ever experience vapor lock was when I had a temporary 383 in my first car ('69 Charger). It came with a 318 which was being rebuilt, but I needed the car so a well-worn 383 went in. The extra heat from the exhausts was an issue. A little aluminum foil around all the rubber line solved it (no return lines on cars that far back). It'd cut out and I'd have to wait for it to cool off to continue on. Also, once the 318 was back in, it eventually got topped with an Edelbrock 750 AFB. The aluminum body rejects heat several times quicker than steel. Fuel percolation was never an issue. Not to say it can't happen, just sayingit's much more likely a hot spot on a fuel line.
 

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Discussion Starter · #11 ·
I'd definitely make sure that fuel return line is hooked up (return back to the fuel tank). The mechanical pump will serve as an effective pressure limiter to the electric pump, so it's probably not flooding from excess volume, unless the fuel return line is capped and the fuel has nowhere to go. Possible the idle speed screw bleeds could be fouled. Start at a high idle. There are 2 screws on the front lower section of the carb. Gently flush them down, then unscrew 1.5 complete turns. Start up, get up a high idle around 1500rpm, then take one screw and slowly screw in 1/2 turn. Engine rpm should vary slightly. Then return to original spot. Now unscrew another 1/2 turn, meaning 2 total turns. Better or worse? Leave it where it's best and repeat with the other screw. What you are looking for is where rpm will rise to highest point in response to adjustment. If one or both are bad, you can screw in or out and it'll basically make no difference. One might work, and the other is like being a dumb post, totally useless. If that happens, you have a problem. Could be internal damage, or possibly just crud. If you see improvement, take a test drive on the new settings. I'm thinking you do have a fuel delivery issue. The electric could be failing and needs time to cool off as you indicated earlier. The tandem pump thing was used, usually to help maintain good fuel supply (and combat vapor locking fuel lines), not that it was needed with a healthy factory system. Sounds like they were having issues when they added that. Hate to say it but unless you can verify adequate fuel supply, I'd scrag both pumps for new ones, mechanical first, then electric if needed. I would test a new mechanical with the electric removed and the line spliced, otherwise the possibly dead electric could restrict flow. I'm in South Mississippi. We know hot weather too. Only time I ever experience vapor lock was when I had a temporary 383 in my first car ('69 Charger). It came with a 318 which was being rebuilt, but I needed the car so a well-worn 383 went in. The extra heat from the exhausts was an issue. A little aluminum foil around all the rubber line solved it (no return lines on cars that far back). It'd cut out and I'd have to wait for it to cool off to continue on. Also, once the 318 was back in, it eventually got topped with an Edelbrock 750 AFB. The aluminum body rejects heat several times quicker than steel. Fuel percolation was never an issue. Not to say it can't happen, just sayingit's much more likely a hot spot on a fuel line.


Ironically enough after a dump run one day, the truck started sputtering and dying out when we hit a hill, and upon inspection of the hoses under the hood, there was a piece of tubing coming off the fuel filter that was just shot, it was easily pinched by hand, and had basically just collapsed internally. We replaced that and figured out that a couple of vacuum lines that were part of the vapor canister system weren't even hooked up, after hooking all that up, it started up and pulled the last three hills home with almost no problems, but it is back to running like crap once it heats up. I'm going to try wrapping the fuel lines in foil to see if that helps along with the carb tune and ignition coil, I'll be doing that tomorrow.
 

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Couple other things, now that you mention it. Get a pack of caps and plugs. Go through and use the appropriate piece to close off every extraneous port under the hood. Cap the vacuum cannister and every other dinky little vacuum line/port you can find. All you need is the big vacuum lines for PCV and power brakes. If yours has a vacuum advance on the distributor (pretty much gone by mid-80's) make sure it's good. Other than that, the other stuff is garbage. Just all potential leaks. The vapor cannister is part of the purge function (emissions crap). If you notice pressure on the fuel tank on hot days, switch to a vented gas cap. Since you don't have the stock carb, the whole purge function is non-functional anyway.
 

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Discussion Starter · #13 ·
Couple other things, now that you mention it. Get a pack of caps and plugs. Go through and use the appropriate piece to close off every extraneous port under the hood. Cap the vacuum cannister and every other dinky little vacuum line/port you can find. All you need is the big vacuum lines for PCV and power brakes. If yours has a vacuum advance on the distributor (pretty much gone by mid-80's) make sure it's good. Other than that, the other stuff is garbage. Just all potential leaks. The vapor cannister is part of the purge function (emissions crap). If you notice pressure on the fuel tank on hot days, switch to a vented gas cap. Since you don't have the stock carb, the whole purge function is non-functional anyway.
Bonus! I will definitely do that.. It does have a vacuum advance dist. But I don't know if it is working.. Thats why I was asking about the timing as I can't see the timing marks through the goofy little cup on the crank since the smog pump is in the way.
 

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Something else. You want to be sure the vacuum line to the distributor is connected to the ported vacuum port, not the full time port on the carb. On the AFB these two ports are on either side of the two idle screw adjusters. Facing the truck, driver side being to your right side, looking at the carb, the ported vacuum port is on the left side of the front of the carb, directly to the left of that side's idle adjuster screw. Cap the port on the right side. If not hooked up to the ported vacuum it'll never run right.
 

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Discussion Starter · #15 ·
Something else. You want to be sure the vacuum line to the distributor is connected to the ported vacuum port, not the full time port on the carb. On the AFB these two ports are on either side of the two idle screw adjusters. Facing the truck, driver side being to your right side, looking at the carb, the ported vacuum port is on the left side of the front of the carb, directly to the left of that side's idle adjuster screw. Cap the port on the right side. If not hooked up to the ported vacuum it'll never run right.
If i'm not mistaken thats how it is hooked up, but if not, I'll set it right.

More pics and audio clip coming tonight.
 

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Discussion Starter · #16 · (Edited)
Ok here's an update. I went to check the gap on the plugs, and the wires fell apart, so I picked up a set of bosch 7mm wires. Attempted the carb tuning and have almost turned the screws all the way out, it still dies when you put it into gear. The gap on every plug was too small, adjusted that. I swear it still has a miss, I wonder if the ICM is going out/bad? I was told it was replaced by my grandpa (who has alzheimers, not the most reliable source I realize), it is blue, which seems odd for a factory color, but who knows...
 

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If the idle mixture screw adjusters have no effect when being adjusted, sounds like you have a carb problem. The engine should not idle at all if totally screwed down. A setting of about 1.5- 2.0 full turns open should be fine.
While a failing ICM doesn't typically cause a "miss" it is possible that it's failing, requiring time to cool off to run again fits that profile. That will get worse and eventually fail. Also, the ballast resistor needs to be replaced (white ceramic----brittle, delicate....don't over-tighten) on firewall near ICM. Fortunately, they're $20 bucks each, give or take. Blue ICM not uncommon for aftermarket, have had them myself. As the production of these things moved the China, those in the know always kept a spare set in the glove box. Just don't last like in the old days. If you get a good one, it will last years.
Another possible cause of the miss could be a little deeper in the ignition, meaning the distributor (single pickup or dual?) Could be a worn distributor shaft bushing in the block causing a wobble that's dropping a cylinder, but that's something to consider after everything else has been dealt with. You typically see that on very high time engines. It can manifest as a low rpm miss that improves as rpms rise.
It sounds like you're finding the basic issues on your own. It needs a tune-up. The carb is still a concern. Funny how on these relatively simple setups (compared to today) problems can still be difficult to ferret out.
 

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Discussion Starter · #18 ·
If the idle mixture screw adjusters have no effect when being adjusted, sounds like you have a carb problem. The engine should not idle at all if totally screwed down. A setting of about 1.5- 2.0 full turns open should be fine.
While a failing ICM doesn't typically cause a "miss" it is possible that it's failing, requiring time to cool off to run again fits that profile. That will get worse and eventually fail. Also, the ballast resistor needs to be replaced (white ceramic----brittle, delicate....don't over-tighten) on firewall near ICM. Fortunately, they're $20 bucks each, give or take. Blue ICM not uncommon for aftermarket, have had them myself. As the production of these things moved the China, those in the know always kept a spare set in the glove box. Just don't last like in the old days. If you get a good one, it will last years.
Another possible cause of the miss could be a little deeper in the ignition, meaning the distributor (single pickup or dual?) Could be a worn distributor shaft bushing in the block causing a wobble that's dropping a cylinder, but that's something to consider after everything else has been dealt with. You typically see that on very high time engines. It can manifest as a low rpm miss that improves as rpms rise.
It sounds like you're finding the basic issues on your own. It needs a tune-up. The carb is still a concern. Funny how on these relatively simple setups (compared to today) problems can still be difficult to ferret out.

I looked at the dist. and rotor/cap, everything looks good. I do wonder about the ICM. The ballast resistor is something I forgot about, but will be replacing.. The current one definitely looks crispy.. Since the ICM is only $23 I'll be replacing that as well..

Engine Video
Exhaust Video
 

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Man, it's worse than I thought. I'm hearing some mis-firing or something in there, surging too. Still a good idea to replace the ignition stuff like we've discussed. I think you're still having a vacuum leak. Start with the carb as suspect number one. If those idle mix screws are ineffective, you definitely have a vacuum leak, most likely from galling in the carb body around those bleeds. Not knowing the history of that carb it's hard to say, but it happens. The sound coming from the carb is all wrong, even for a stock engine. It just sounds bad. Idling way too high, which can also indicate a vacuum leak. That thing should sit there and purr silky smooth at 650 rpm idle in gear like it's nothin'.
 

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Discussion Starter · #20 · (Edited)
That thing should sit there and purr silky smooth at 650 rpm idle in gear like it's nothin'.
I agree. I will have the money to replace the ICM and ballast tomorrow, so I will do that as well as trash the smog pump and time the engine, see how it runs after that... I wish it had a tach as I can't judge its rpm by ear with all the extra noise that thing makes..
 
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