And more troubles....timing?

[Orangecrush]

And yet another problem I'm having: Hard stumble on light acelleration. Usuallly right around 1500 rpm, while lightly to moderately acellerating, the engine really stumbles. If it's cold, it will usually stall.

I used to think it was lack of spark or carb related (and it could be); but now, I am leaning towards a lack of initial timing (I think it's 12 now.....or at least that's what's scratched on the vacuum advance unit). If I floor it, it is fine and doesn't stumble. If I acellerate hard, it doesn't stumble. It's just light to moderate acelleration tht makes it die for a second.

I know NOTHING about how to adjust my timing. Is it easy? Can anyone walk me through?? I think 14 of initial may be best. Or, maybe the vacuum advance isn't working properly altogether?? Oh yea, I'm running a brand new Petronix distributor .

Any suggestions??

Thanks!!

 

[BLADE262US]

I would look closely at your accelerator pump . /emoticons/[email protected] 2x" width="20" height="20" />

 

[STLKIKN]

I second a possible carb problem.

Either accelerator pump, or if the Demon has "tuneable" needles and seats like an Edelbrock, you may try and find a slightly smaller set and try them.

 

[Orangecrush]

I second a possible carb problem.Either accelerator pump, or if the Demon has "tuneable" needles and seats like an Edelbrock, you may try and find a slightly smaller set and try them.

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Hmmmm, well two votes for fuel related.....there is a problem with the carb. No question about it. The front float is always full right to the top. This causes a flooding problem on the highway at cruise. I thought the off-idle stumble was something else though.

As for the acellerator pump, when I manually operate the carb, both jets seem to squirt fuel right away with no slack or anything. When I stomp on it, there is no stumble also.....which leads me to think the acel. pump is okay. But, I'm really not an expert.

I'll download the Demon manual and see if there is some way I can adjust the float level......I'm a carb novice.

Thanks

 

[Broncoholics]

I hope you have a clean fuel filter first.

Sounds to me like you need a new carb or a rebuild.

If you think its timming you can always play around with it tithout a light. Loosen the base bolt and turn it by hand, you will hear the motor change. You will have to adjust the idle on the carb accordingly. Drive around, see what works. You will have more power by advancing it but you can get overheating problems and even burn a hole in a piston. Make small changes and drive around.

 

[Orangecrush]

I hope you have a clean fuel filter first.Sounds to me like you need a new carb or a rebuild.

If you think its timming you can always play around with it tithout a light. Loosen the base bolt and turn it by hand, you will hear the motor change. You will have to adjust the idle on the carb accordingly. Drive around, see what works. You will have more power by advancing it but you can get overheating problems and even burn a hole in a piston. Make small changes and drive around.

21108[/snapback]

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Yea, it's got to be air:fuel ratio that's causing the stumble. I would guess, too lean on the primary side as it also sometimes get's and STAYS in a stumble/surge situation on the freeway. The other thing that's going on is the carb float (primary) is full to the top and then some when you look at the site window. I wonder if this situation is causing the highway stumble or is it just lean and dying at cruise.

What a PITA! This is exactly what I was trying to avoid when I decided to pay a little more for the BG Demon carb. Nice choice :angry:

 

[BLADE262US]

LOL thats what falls into the shit happens now you have to wipe and move on . Im not sure but I think those carbs adjust the float level like a holley so if theres a big ***** on top of the float bowl then crack it loose and I think the nut under it you have to turn in to lower the float level then tighten the ***** again to lock it in position . Im thinking that if you look down the carb and crack the throttle wide open fast and hold it there it should take like 2 or 3 seconds for the squirters to quit squirting if there done in a sec or under there is not enough volume or something is out of adjustment be like if you had a mouth full of gas and were trying to keep a fire going if you spit it all at once there is a big flash and its all over the fire goes out but if you keep a steady stream going it will burn the fire longer till the rest catches up to keep it burning . LOL how do you like that for an analogy and I wouldnt suggest trying that at home . Or anywhere else for that matter . If you decide to try another carb I would suggest an edelbrock 600 cfm electric choke I have used 2 brand new ones and have no problems my plow truck starts like a fuel injected vehicle in the dead of winter I have been wanting to try one of the new thunder AVS carbs maybe on my next project . I would really think about trying a new carb though , What kind of distributor do you have ? /emoticons/[email protected] 2x" width="20" height="20" />

 

[Orangecrush]

LOL thats what falls into the shit happens now you have to wipe and move on . Im not sure but I think those carbs adjust the float level like a holley so if theres a big ***** on top of the float bowl then crack it loose and I think the nut under it you have to turn in to lower the float level then tighten the ***** again to lock it in position . Im thinking that if you look down the carb and crack the throttle wide open fast and hold it there it should take like 2 or 3 seconds for the squirters to quit squirting if there done in a sec or under there is not enough volume or something is out of adjustment be like if you had a mouth full of gas and were trying to keep a fire going if you spit it all at once there is a big flash and its all over the fire goes out but if you keep a steady stream going it will burn the fire longer till the rest catches up to keep it burning . LOL how do you like that for an analogy and I wouldnt suggest trying that at home . Or anywhere else for that matter . If you decide to try another carb I would suggest an edelbrock 600 cfm electric choke I have used 2 brand new ones and have no problems my plow truck starts like a fuel injected vehicle in the dead of winter I have been wanting to try one of the new thunder AVS carbs maybe on my next project . I would really think about trying a new carb though , What kind of distributor do you have ?  /emoticons/[email protected] 2x" width="20" height="20" />

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Man, that's so helpful. I really appreciate it. First, yes the Demon is exactly like a HOlley and there is a big hex head hut or something on top of both ends (see what a carb expert I am?). I will ***** with it and see if I can lower the fuel level. It should be like half full right?? I have heard from MANY people tht Demons are machined and that little pieces of metal can stick the float open and thus flood. ****, I'll just start f*$ing with stuff and see if I can fix it. If you have any advice on opening and cleaning the float, lay it on me so I don't pull my hair out tonight.

The goofy thing with this carb is that it doesn't die at all when you go stratight to WOT. It's just the type of acceleration you'd do in normal, everyday situations that screws it up. And don't get me started on how it likes to die when cold......so embarassing having this very sweet Bronco that stalls and then doesn't want to start 3 times leaving my own driveway. :blush:

As for Edelbrock....I've had 2 mechanics tell me they wouldn't even put them on my car??? They said they are not like the old style Carters (which they said were the best). I had an old Carter AFB 600 (I think) on my '65 Stingray. I never had to ***** with it and it ran like fuel injection.....and that was with a serioius cam. I wish I could get my hands on one of those.

 

[BLADE262US]

I have a couple of those AFB,s sitting on the shelf I ran them forever . There a good carb pretty much the edelbrock is the very same carb only real difference that I have found is that on a carter the 2 big screws in the front are air bleed screws so the farther out you back them the more air it lets in thus leaning the idle mixture on an edelbrock they work just the oposite there fuel metering screws so the farther out you back them the more fuel it allows to enter the mix richening it . After running the 2 of them Id say either of them is a very good choice I would stick with the electric choke version of whatever one you choose and for the mechanics that are telling you that there junk . HE HE are they helping you with your demon ? /emoticons/[email protected] 2x" width="20" height="20" />

 

[BLADE262US]

Another thing you never said what kind of distributor your running I kinda need to know this I have another thought as to what you may be experiencing . /emoticons/[email protected] 2x" width="20" height="20" />

 

[Orangecrush]

Another thing you never said what kind of distributor your running I kinda need to know this I have another thought as to what you may be experiencing .  /emoticons/[email protected] 2x" width="20" height="20" />

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It's a brand new Pertronix Ignitor. I'm using a pertronix coil as well. I have vacuum advance set at 12 degrees initial (or so it says). The manifold is Edelbrock performer. I'm using a 2" spacer on the manifold. What else....it's a 351W. I'm running a 230/230@050 cam on a 110 lsa. The manifold vacuum seems good (16" at idle). Fuel pressure is good. The fuel filter is good (just replaced to be sure). The choke is electric and seems to work perfectly. All wires and plugs are brand new. The last time I pulled a plug, it wsa nice and even tan. Could that 2" spacer be causing any problems??? It should make things better if anything, I would think.

The guy who originally did my restoration (a/c, leather dash, gauges, etc) insisted that this go in. Well, he meant well;but, I know much more about being a mechanic than he does. He could have screwed up anything. However, it ran so poorly after getting the truck back, I took it to my old tuner who used to do my Corvette. He monkied with it but the bigger job was the new cam. So, he ended up focusing on the cam and must have forgot about the stumble issue. I just don't have the patience to bring it back over to him and be without it for a couple more days and also have to pay him again (for the same job). I'm just sick of it and would really like to solve this on my own. Plus, that will feel so good, right?

 

[BLADE262US]

HMMMMM I think I would check for leaks around that spacer . The spacer shouldnt hurt anything it will keep the fuel cooler as the carb isnt sitting on the intake cooking . Im not familiar with that distributor on the stock ford distributors theres a mechanical advance under the plate you see when you take the cap off . They sometimes well most of the time corrode up and dont move anymore or the bushings will break out of them and it will do all kinds of stupid stuff . Im not sure how the one you have works . Do you have it on a timed vacuum port ( only has vacuum when throttle is open ) or a full vacuum port ( vacuum on it all the time ) Im thinking that it should be on a full vacuum port so check that . Did the guy degree the cam in or did he just toss her in the hole and send it on the way ? If its holding steady vacuum at an idle like that it should be ok . Check that vacuum line to the distributor because you said it takes off good from a dead stop when you crack the throttle wide open the vacuum falls to nothing which if you have it on a full vacuum port it would ****** the timing and if you eased into the throttle the vacuum drop would be differnt . Hmmmmm need to know timed vacuum line or full . /emoticons/[email protected] 2x" width="20" height="20" /> Gotta go to work

 

[Orangecrush]

HMMMMM I think I would check for leaks around that spacer . The spacer shouldnt hurt anything it will keep the fuel cooler as the carb isnt sitting on the intake cooking . Im not familiar with that distributor on the stock ford distributors theres a mechanical advance under the plate you see when you take the cap off . They sometimes well most of the time corrode up and dont move anymore or the bushings will break out of them and it will do all kinds of stupid stuff . Im not sure how the one you have works . Do you have it on a timed vacuum port ( only has vacuum when throttle is open ) or a full vacuum port ( vacuum on it all the time ) Im thinking that it should be on a full vacuum port so check that . Did the guy degree the cam in or did he just toss her in the hole and send it on the way ? If its holding steady vacuum at an idle like that it should be ok . Check that vacuum line to the distributor because you said it takes off good from a dead stop when you crack the throttle wide open the vacuum falls to nothing which if you have it on a full vacuum port it would ****** the timing and if you eased into the throttle the vacuum drop would be differnt . Hmmmmm need to know timed vacuum line or full  .  /emoticons/[email protected] 2x" width="20" height="20" />  Gotta go to work

21139[/snapback]

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Okay, and the latest excitement is........I adjusted the floats by turning the nut as to lower the brass threaded rod. I then put the ***** back in. The float looks slightly lower; but, I need to check further.

Here's another twist, I hogged on it just a few minutes ago...ran it up to 5500 rpm at WOT, then let off the accelerator and turned into my office building. It immediately started stumbling and running REALLY ROUGH, and wanted to stall. If I didn't keep my foot in it, it would have stalled; but had ZERO power. I then shut it off, waited 10 seconds, and restarted. All seemed fine again.

What do you think this is? It seems simply flooded to me, which would bring us right back to the float issue, right?? Man this is fun :huh:

Checked for vacuum leak at base of carb and spacer to manifold but found none. I used a propane torch to see if I could **** some propane into the engine, but no elevated rpm was noticed.

Vacuum lines: there are only 3 hooked to the carb. 1) hooked to power brakes and I think this one is full vacuum 2) hooked to a/c switch...I think this is above the plates 3) hooked to the vac advance unit....pretty sure this is also above the throttle plates.

Good lord, for $250 I could just bolt on another stupid carb......this is nuts.

 

[Broncoholics]

You might look into the Edelbrock. I never had problems with mine unless off road. Steep angles would load up the carb like most. But Q-jet, like I run now works well at all angles (for off road rigs). The downside is they can puke on you as well and need to be adjusted here and there. The best carb I found was the Carter 600. Ran like a million bucks on my old K5 blazer that always ran bad. Passed emmissions without tuning. Can't argue with that!

 

[Orangecrush]

Okay, just got off the phone with another old school carb. guy....been doing it for 39 years. I described my setup to him. He immediately said "get rid of that stupid spacer. It's you problem." I told that I though a spacer created better mixture, velocity and signal??? He said "no, an open spacer just creates a dead spot where there is no signal. I guarantee that if you take off the spacer, the stumble will disappear."

??? Can this be true. He didn't say "well....it coulld be Or, it might be. He was very quick to say the only problem is absolutely the spacer and to never use one. He did say the 4-hole variety are okay; but never to use an open one unless you're a circle track racer.

I'm still 100% sure the carb needs work as it keep flooding; but, I'm hoping that his advice will solve the off-idle stumble.

[-o<

 

[BLADE262US]

Hello I didnt know your spacer was the open one yeah that could be your problem there more for high rpm . I would take it off and see very well could be try to get a 4 hole one if it is the problem . /emoticons/[email protected] 2x" width="20" height="20" />

 

[Bully Bob]

Just a side thought....a leaking power brake booster has simular symptoms. Sometimes can be heard inside cab at the firewall.

 

[Bully Bob]

Just a side thought....a leaking power brake booster has simular symptoms. Sometimes can be heard inside cab at the firewall. B)

 

[Orangecrush]

Just a side thought....a leaking power brake booster has simular symptoms.  Sometimes can be heard inside cab at the firewall. B)

21203[/snapback]

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Well, took off the spacer. It turned out to be a 4-hole after all. I just bolted the carb to the manifold.....same thing ( No change at all. Low rpm just has zero power to the point of wantig to die....once it gets to 1400 rpm, the stumble comes in and the revs drop back to 1200 before catching again and then the engine comes to life and starts pulling. What goes on before 1500 rpm??

Well, I'll fiddle with advance a little next. I'll also pull the vaccum line to the power brakes, plug the port and see if things clear up. Then, I'll drop the truck off with the carb. guy.

Which way do you turn the distributor to advance the initial timing?