So, seriously:I'm sure that a carb could be set up for that, but EFI pretty much solved most of those issues. If I lived in a hotter climate I would probably just use manifold vacuum but here in northern Idaho I have to contend with cold weather warmup much more often, the only exception being haying season and I have never bothered to re-tune the engine just for that. I have the BIG radiator in the truck so it never overheats.
Joe
Joe
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Anonymous
Guest
I'm getting more confused with all this talk about differant sources of vacuum.....I spent some more time in the garage last night and here's some more observations;
I pulled the hose off the PCV and plugged it (left in connected to the manifold inlet) - rpm went down 200 rpm. I tried a differant PCV and it did not change things.
I tried running it without the fuel filter- it seemed tad smoother, but not much. I put in a new filter- no differance. Could it be the fuel pump? (I think not as I did not have this problem on the 170, and all parts I'm using except the new carb were on the 170) I wouldn't think the fuel pump going would cause high vacuum advance :roll:
I changed cap, rotor, and condensor- no help. Disconnected vac. line to trans- no help. I'm wondering if it is a fuel or mixture problem.
I have disconnected the vac. advance for the time being- the car does not run better, but at least I'm not going down the freeway with too much advance and risking damage. I can't hear if there's detonation due to the exhaust leak (getting fixed tomorrow since no headers avail. ) but plug tips are white now.
Today I noticed that while at cruising speed, with vac. advance diconnected, if I pull out the manual choke the engine runs and performs smoother- not perfect, but better. Maybe the carb IS too lean- would that cause the timing problem
:
I am going to put the 1100 back on tonight ( had misfiring or "surging" going down the road on this 200 with it but not as bad as with the YF, not at all on the 170) and put the biggest jet I have in it to see if that helps. Doug said not to drill out the jet on the YF or that will ruin it, so if it is running too lean I'll have to figure that one out when I cross that bridge...
Addo said "What if the carb were designed to work in conjunction with a thermo-vacuum switch?" I'm not sure exactly what this means, but I know this is a non-thermactor carb and dist. The distributor that was on the engine when I bought it had two vacuum ports- one was plugged. I am running the single advance dist. (from '68 mustang) that I had in my 170.
I know nothing about an allen screw inside the vacuum port (and there is only one port on this carb) but I will look at that tonight before I put the 1100 back on.
One other thing - The YF has an automatic choke but came without a tube, so I transferred the manual choke off my 2100 to the YF. I assume the choke tube pulls air through into the carb and thought this might act as a vacuum leak with no tube connected to the exhaust manifold, so I plugged it. It had no effect on the current problem, though.
So, the questions are; How do I know if the fuel pump is going, can I adjust the vacuum at the port, and will richening up the mixture (with the autolite 1100) help? I'm going to look at the latter two tonight.
Thor
PS- Is there something that could have been done wrong when the engine was assembled- like the timing gears not being lined up correctly, or something else- that could cause this?
I pulled the hose off the PCV and plugged it (left in connected to the manifold inlet) - rpm went down 200 rpm. I tried a differant PCV and it did not change things.
I tried running it without the fuel filter- it seemed tad smoother, but not much. I put in a new filter- no differance. Could it be the fuel pump? (I think not as I did not have this problem on the 170, and all parts I'm using except the new carb were on the 170) I wouldn't think the fuel pump going would cause high vacuum advance :roll:
I changed cap, rotor, and condensor- no help. Disconnected vac. line to trans- no help. I'm wondering if it is a fuel or mixture problem.
I have disconnected the vac. advance for the time being- the car does not run better, but at least I'm not going down the freeway with too much advance and risking damage. I can't hear if there's detonation due to the exhaust leak (getting fixed tomorrow since no headers avail. ) but plug tips are white now.
Today I noticed that while at cruising speed, with vac. advance diconnected, if I pull out the manual choke the engine runs and performs smoother- not perfect, but better. Maybe the carb IS too lean- would that cause the timing problem
: I am going to put the 1100 back on tonight ( had misfiring or "surging" going down the road on this 200 with it but not as bad as with the YF, not at all on the 170) and put the biggest jet I have in it to see if that helps. Doug said not to drill out the jet on the YF or that will ruin it, so if it is running too lean I'll have to figure that one out when I cross that bridge...
Addo said "What if the carb were designed to work in conjunction with a thermo-vacuum switch?" I'm not sure exactly what this means, but I know this is a non-thermactor carb and dist. The distributor that was on the engine when I bought it had two vacuum ports- one was plugged. I am running the single advance dist. (from '68 mustang) that I had in my 170.
I know nothing about an allen screw inside the vacuum port (and there is only one port on this carb) but I will look at that tonight before I put the 1100 back on.
One other thing - The YF has an automatic choke but came without a tube, so I transferred the manual choke off my 2100 to the YF. I assume the choke tube pulls air through into the carb and thought this might act as a vacuum leak with no tube connected to the exhaust manifold, so I plugged it. It had no effect on the current problem, though.
So, the questions are; How do I know if the fuel pump is going, can I adjust the vacuum at the port, and will richening up the mixture (with the autolite 1100) help? I'm going to look at the latter two tonight.
Thor
PS- Is there something that could have been done wrong when the engine was assembled- like the timing gears not being lined up correctly, or something else- that could cause this?
Thor,
Hang in there, you'll figure it out yet
It seems unlikely that the fuel pump would only cause trouble at low/mid-range. Usually when poor fuel delivery is an issue it won't run well at high speed and you said that it runs fine when pulling hard at higher rpm, which is when it burns the most fuel. Poor ignition usually shows up then too. I think there is something wrong with the carb. Definitely leave the vacuum advance unhooked until the rest of the system is dialed in. Some distributors have an adjustable vacuum advance unit, there is an allen head gizmo inside the vacuum nipple that can be tweaked to modify the amount of advance. I am not aware of any carbs that were adjustable, but then there is a lot that I don't know 
Joe
Hang in there, you'll figure it out yet
It seems unlikely that the fuel pump would only cause trouble at low/mid-range. Usually when poor fuel delivery is an issue it won't run well at high speed and you said that it runs fine when pulling hard at higher rpm, which is when it burns the most fuel. Poor ignition usually shows up then too. I think there is something wrong with the carb. Definitely leave the vacuum advance unhooked until the rest of the system is dialed in. Some distributors have an adjustable vacuum advance unit, there is an allen head gizmo inside the vacuum nipple that can be tweaked to modify the amount of advance. I am not aware of any carbs that were adjustable, but then there is a lot that I don't know Joe
goinbroke2
Well-known member
When I first started reading this thread I thought to myself, too lean. Reading more, and seeing the engine smooth out with the choke pulled a bit confirmed it.
IF, it was too much timing, then by pulling off the vac line and manually setting max mechanical advance around 34-38 and going for a drive would prove/disprove it. I don't think it would. So, if it's not, what else causes surging or light load miss? Lean carb.
Now here's where drag racing experience helps, you also mention you have an exh leak at the manifold? Guess what? Which ever port is leaking will be your leanest port! I think the carb is jetted too lean, and having an exh leak at the head put it over the top and turned it into a misfire situation.
I've seen exh temps on an engine on the dyno go from 1180-1200(average) to one cyl going to 1350 and developing a miss when the header gasket blew on a pull. (yes 1350 is too high)!
Also, white plugs? LEAN!
Just for giggles though, pull your plugs and see which is the whitest. I'm betting it's the same cyl that's also leaking exh.....
Oh yeah, put in a tee fitting in the fuel line and run the guage up under the wiper blade. Then go for a drive and see what your fuel pressure is, at highway speed. shouldn't go below 5lb's or so. Just keep the guage outside the car for safety's sake in case a leak developes. Fuel over the roof messes up a paint job, but a fuel leak in the car at 60mph....
IF, it was too much timing, then by pulling off the vac line and manually setting max mechanical advance around 34-38 and going for a drive would prove/disprove it. I don't think it would. So, if it's not, what else causes surging or light load miss? Lean carb.
Now here's where drag racing experience helps, you also mention you have an exh leak at the manifold? Guess what? Which ever port is leaking will be your leanest port! I think the carb is jetted too lean, and having an exh leak at the head put it over the top and turned it into a misfire situation.
I've seen exh temps on an engine on the dyno go from 1180-1200(average) to one cyl going to 1350 and developing a miss when the header gasket blew on a pull. (yes 1350 is too high)!
Also, white plugs? LEAN!
Just for giggles though, pull your plugs and see which is the whitest. I'm betting it's the same cyl that's also leaking exh.....
Oh yeah, put in a tee fitting in the fuel line and run the guage up under the wiper blade. Then go for a drive and see what your fuel pressure is, at highway speed. shouldn't go below 5lb's or so. Just keep the guage outside the car for safety's sake in case a leak developes. Fuel over the roof messes up a paint job, but a fuel leak in the car at 60mph....
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Anonymous
Guest
hmmm...Hey sedanman...looks like we might have similar problems. only difference is my bored out carb, bigger jet and much tightened accelerater/metering needle screw. my plugs arent showing as white now that i have the timing set at a decent spot (for the setup) but i had em pretty white...although i think it was too hot cause i never had the ash (or is it too hot with the ash?) but i too have a quite leaky manifold but its at the front and rear (last 2 cylinders) so i figgured it was normal because they were normally leaner being the last 2 cylinders. I dont have the vacuum advance hooked up, I'll try having it hooked up to the carb, but i'm not sure how much vaccum i get from it (i'll check it later) right nowthe vac advance is disconnected...I used to have it hooked up todirect manifold vacuum, and that was allright, but it didnt seem as good for power (which is more what i want)...it did run smoother though when it was hooked up to manifold vacuum.
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Anonymous
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Well....i ended up swapping alternators because i didnt like the noise it was making....and it ended up running smoother after...so i think my alternator was on its way out. I also hooked up my vac advance to the carb port, It just so happens that the only allen key I'm missing happens to be the one i need to possibly adjust the screw...is it hallow, i use a smaller one and it goes in all the way, but i can feel around near the front and it feels like i might be able to adjust it....with the next size up....but i need to try it like it is first.
It had no effect because the hot air connection simply provides a heat source for the bi-metallic spring that activates your choke. There is no vacuumm on the carb side, and there should be no exhaust coming from the manifold side.Sedanman":2qutw64o said:
I think I might be inclined to try a single nipple vacuum advance unit, but personally, I still think the root cause of your surging problem is cruise mixture related. The fact your engine ran smoother with the choke partially closed confirms that for me - reduced air flow and increased fuel delivery, in other words, went away from lean.
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Anonymous
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Falcon62":34ac4u25 said:It had no effect because the hot air connection simply provides a heat source for the bi-metallic spring that activates your choke. There is no vacuumm on the carb side, and there should be no exhaust coming from the manifold side.Sedanman":34ac4u25 said:
I think I might be inclined to try a single nipple vacuum advance unit, but personally, I still think the root cause of your surging problem is cruise mixture related. The fact your engine ran smoother with the choke partially closed confirms that for me - reduced air flow and increased fuel delivery, in other words, went away from lean.
Phil,
I thought the heat choke actually used a tiny vacuum line (connection/tunnel) within the carb to draw the hot air into the choke area and then down into the carb. Isn't that what one of the tiny ports on the bottom of an 1100 is for?
Then again I could be way off..
Steve-O
USN and still active....
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Anonymous
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steve...that is my understanding too
heat...with a tube running to choke
water...with a hose running next to choke
electric...self explainitory
manual...same
heat...with a tube running to choke
water...with a hose running next to choke
electric...self explainitory
manual...same
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Anonymous
Guest
Okay,
Last night I took the YF off, and put on my 1100 (for a 170). I swapped the 59f jet that was in it for a 69f- the biggest one I have. The car does not idle as well as it did with the YF, but revs freely and does not misfire. I went for a drive, and with the small carb it’s definitely slower now, but the misfire/hesitation is gone- so this MIGHT mean that the YF is running too lean. Vacuum gauge readings at the intake (not the carb) were a just a bit higher than with the YF, at 20-21.5cm throughout the rpm range
However, things get more confusing from here on. When I did the timing check again with the autolite at 500 rpm intervals, with the vacuum advance hooked up, the timing figures were not any different than they were with the advance disconnected- exactly the same as I reported for the YF with the vac. Advance not connected. I thought that the autolite carbs use ported vacuum at low speeds, and the SCV kicks in at higher rpm. I hooked up my vacuum pump to the vacuum line on the carb and pumped away- I could hear the air sucking through the port in the carb throat, so I know it’s not plugged. I do believe that the SCV is not working as there is not further advance at high rpms, and the piston/ diaphragm in the center does not move when I rev the engine. But why no advance at part throttle?
Being that the autolite is not giving any advance at all (no wonder my 170 seemed so slow!), I don’t know how much vacuum advance is “normalâ€, so it’s really hard to tell what has been “fixed†and what has not. The only thing that is obvious to me is that the YF is running way too lean- but is that due to poor A/F mixture/jetting, or some sort of internal vacuum problem? Can too lean a mixture cause high vacuum? That carb is intended for this engine, so I’d be surprised they jetted it so lean.
I can drive it with the 1100 for the moment, but the problem has not been solved. I’m wondering if there’s something they messed up in the remanufacturing process. Mustang Geezer said not to drill out the jet in a YF (see "Aftermarket air cleaner housings" thread) so changing the mixture will be another ballgame. I tried sticking my smallest allen wrench inside the vacuum port, but did not "feel" anything. Since I did not use this carb before it was rebuilt, I have no baseline to go from. Where do I go from here- exchange the YF for another one, or play with the jetting adjustment?
Thor
BTW- regarding the alternator theory, I've had two differant generators on the engine since I installed it. I plan to do the alternator conversion- but not now! My exhaust leak is where the pipe connects to the manifold- not where the manifold bolts to the head. All plugs are uniform in color.
Last night I took the YF off, and put on my 1100 (for a 170). I swapped the 59f jet that was in it for a 69f- the biggest one I have. The car does not idle as well as it did with the YF, but revs freely and does not misfire. I went for a drive, and with the small carb it’s definitely slower now, but the misfire/hesitation is gone- so this MIGHT mean that the YF is running too lean. Vacuum gauge readings at the intake (not the carb) were a just a bit higher than with the YF, at 20-21.5cm throughout the rpm range
However, things get more confusing from here on. When I did the timing check again with the autolite at 500 rpm intervals, with the vacuum advance hooked up, the timing figures were not any different than they were with the advance disconnected- exactly the same as I reported for the YF with the vac. Advance not connected. I thought that the autolite carbs use ported vacuum at low speeds, and the SCV kicks in at higher rpm. I hooked up my vacuum pump to the vacuum line on the carb and pumped away- I could hear the air sucking through the port in the carb throat, so I know it’s not plugged. I do believe that the SCV is not working as there is not further advance at high rpms, and the piston/ diaphragm in the center does not move when I rev the engine. But why no advance at part throttle?
Being that the autolite is not giving any advance at all (no wonder my 170 seemed so slow!), I don’t know how much vacuum advance is “normalâ€, so it’s really hard to tell what has been “fixed†and what has not. The only thing that is obvious to me is that the YF is running way too lean- but is that due to poor A/F mixture/jetting, or some sort of internal vacuum problem? Can too lean a mixture cause high vacuum? That carb is intended for this engine, so I’d be surprised they jetted it so lean.
I can drive it with the 1100 for the moment, but the problem has not been solved. I’m wondering if there’s something they messed up in the remanufacturing process. Mustang Geezer said not to drill out the jet in a YF (see "Aftermarket air cleaner housings" thread) so changing the mixture will be another ballgame. I tried sticking my smallest allen wrench inside the vacuum port, but did not "feel" anything. Since I did not use this carb before it was rebuilt, I have no baseline to go from. Where do I go from here- exchange the YF for another one, or play with the jetting adjustment?
Thor
BTW- regarding the alternator theory, I've had two differant generators on the engine since I installed it. I plan to do the alternator conversion- but not now! My exhaust leak is where the pipe connects to the manifold- not where the manifold bolts to the head. All plugs are uniform in color.
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Anonymous
Guest
BTW, what is a "thermactor"? I went by the parts store yesterday looking for something else, but asked to check the parts book they ordered the carb from. There was a listing for thermactor and non-thermactor equipped. Since I don't have any emissions controls (besides the PCV) and am running '68 mustang single advance distributor I got the non- thermactor carb.
Thor
Thor
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Anonymous
Guest
To adjust the vacuum advance, the hex key is inserted into the nipple on the distributor not the port on the carb. Some vacuum cans do not have adjustable vacuum diaphrams.
You might try plugging the vacuum port on the carb and then hooking your vacuum pump to the nipple on the distributor. As the engine is running, pull a vacuum with the pump and note any change in the ignition advance with your timing light. This will let you know if the vacuum advance mechanism is working. If it works, then it sounds like the spark control valve may be the problem. I see no reason to run the distributor connected to the spark control valve with a 1968 distributor. I don't believe the SCV was used on 1968 cars with vacuum and centrifugal advance distributors. But I may be wrong. I would hook the distributor up to manifold vacuum and check the timing curve again.
Doug
You might try plugging the vacuum port on the carb and then hooking your vacuum pump to the nipple on the distributor. As the engine is running, pull a vacuum with the pump and note any change in the ignition advance with your timing light. This will let you know if the vacuum advance mechanism is working. If it works, then it sounds like the spark control valve may be the problem. I see no reason to run the distributor connected to the spark control valve with a 1968 distributor. I don't believe the SCV was used on 1968 cars with vacuum and centrifugal advance distributors. But I may be wrong. I would hook the distributor up to manifold vacuum and check the timing curve again.
Doug
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Anonymous
Guest
Doug,
I'm aware that the 1968 up cars do not use an SCV- this is one of the reasons I went to the YF besides my carb being for a 170, as well and that I just have not been happy with the autolite carbs in general. From what others have said, running a carb with SCV with the later distributor should give too much advance.
I should be getting some vacuum from the carb at low rpms even if the SCV does not work, right?
I have put the vacuum pump on the distributor advance - at idle, it took 10cm/26in of air to advance total timing to 40 degrees with the vacuum pump. With the engine not running, looking at the distributor plate and mechanism with the cap off, it took 12cm/20in to advance it all the way until the plate stopped rotating.
I'm aware that the 1968 up cars do not use an SCV- this is one of the reasons I went to the YF besides my carb being for a 170, as well and that I just have not been happy with the autolite carbs in general. From what others have said, running a carb with SCV with the later distributor should give too much advance.
I should be getting some vacuum from the carb at low rpms even if the SCV does not work, right?
I have put the vacuum pump on the distributor advance - at idle, it took 10cm/26in of air to advance total timing to 40 degrees with the vacuum pump. With the engine not running, looking at the distributor plate and mechanism with the cap off, it took 12cm/20in to advance it all the way until the plate stopped rotating.
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Anonymous
Guest
I may not be interpreting what you are asking correctly, but typically, at idle (low rpm) the engine vacuum is nearly at its maximum, because the throttle plates are closed. In the driveway (under no load), you can rev the engine and see the vacuum rise substantially higher than the vacuum at idle. However, when the egine is placed under a load, you will not see vacuum reading nearly that high.
If you are asking whether or not you should see some vacuum at idle via the distibutor line connection with a spark control valve equipped carb, the answer is yes, but not likey that much. The SCV sources both a ported and venturi source vacuum.
With the carb and distributor combo that you are running , I believe you should tie into a vacuum source that is below the throttle plates and plug off the carb's port to the distributor.
You mention that it did not appear that the vac advance was any different than with the YF carb when its line was disconnected. This would indicate you are not getting any vacuum advance from the SCV. If the valve is stuck, you might only be getting venturi vacuum. At low rpm's, not much air is flowing thru the venturi so the vacuum signal is weak. What kind of vacuum readings are you getting from the line that is connected to the carb's distributor port?
Your distributor was calibrated to run on manifold vacuum. In order to respond to venturi vacuum, the diaphram would have to be weaker and be calibrated differently, because the venturi vacuum signal is not as strong as the manifold vacuum signal. Connecting your distributor to the stock distributor SCV controlled port may not provide enough vacuum to move the diaphram in your distributor. Your manifold vacuum readings sound good. Connect the distributor to a manifold source, and adjust the vacuum advance diaphram tension if your total advance is too high.
Doug
If you are asking whether or not you should see some vacuum at idle via the distibutor line connection with a spark control valve equipped carb, the answer is yes, but not likey that much. The SCV sources both a ported and venturi source vacuum.
With the carb and distributor combo that you are running , I believe you should tie into a vacuum source that is below the throttle plates and plug off the carb's port to the distributor.
You mention that it did not appear that the vac advance was any different than with the YF carb when its line was disconnected. This would indicate you are not getting any vacuum advance from the SCV. If the valve is stuck, you might only be getting venturi vacuum. At low rpm's, not much air is flowing thru the venturi so the vacuum signal is weak. What kind of vacuum readings are you getting from the line that is connected to the carb's distributor port?
Your distributor was calibrated to run on manifold vacuum. In order to respond to venturi vacuum, the diaphram would have to be weaker and be calibrated differently, because the venturi vacuum signal is not as strong as the manifold vacuum signal. Connecting your distributor to the stock distributor SCV controlled port may not provide enough vacuum to move the diaphram in your distributor. Your manifold vacuum readings sound good. Connect the distributor to a manifold source, and adjust the vacuum advance diaphram tension if your total advance is too high.
Doug
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Anonymous
Guest
i dont get any readings from the carb port at idle and a tiny bit when i rev it up to about 2000, but i notice that when i drive i get detonation now, which means i'm getting too much advance, thats only when i floor it....could i install a valve to adjust how much vacuum goes through rather than adjusting a hex? i cant retard the timing a whole lot more without it running rougher...right now the timing is in its sweet spot, it idles the smoothest and the exhaust sounds way cleaner...i still have a problem of what seeems like a vacuum leak when the car is cold, but if i warm up the car for 10 min in the morning its fine...not sure why that is, but its pretty much perfect except for the detonation at WOT from the vac advance and the leaky problem when its cold.
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Anonymous
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Dave,
I'm gonna assume your carb does not have the spark control valve and that you do not have a Loadamatic distributor on your '78.
Anyway, when you are at WOT, there is little to no vacuum signal with which to operate the vacuum advance whether it is from a ported source above the throttle plates or a manifold source. If you have pinging at WOT, you have too much initial or centrifugal advance. More than likely it is too much initial advance. If you get pinging at part throttle acceleration, then you might have too much vacuum advance and or too much initial advance. You can get it to idle better by using a manifold source for the vacuum advance at idle conditions. If your distributor has two fitting for vacuum, you might want to try running it without the retard fitting connected to vacuum. Then back off the initial timing. This may give you the smooth idle you want yet reduce the overall advance at WOT by dropping out the vacuum advance component at WOT.
Doug
I'm gonna assume your carb does not have the spark control valve and that you do not have a Loadamatic distributor on your '78.
Anyway, when you are at WOT, there is little to no vacuum signal with which to operate the vacuum advance whether it is from a ported source above the throttle plates or a manifold source. If you have pinging at WOT, you have too much initial or centrifugal advance. More than likely it is too much initial advance. If you get pinging at part throttle acceleration, then you might have too much vacuum advance and or too much initial advance. You can get it to idle better by using a manifold source for the vacuum advance at idle conditions. If your distributor has two fitting for vacuum, you might want to try running it without the retard fitting connected to vacuum. Then back off the initial timing. This may give you the smooth idle you want yet reduce the overall advance at WOT by dropping out the vacuum advance component at WOT.
Doug
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Anonymous
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66 Fastback 200":2ayec9ik said:
hmmm....I never had the pinging before i hooked up the vac advance though. I'll hook it up to manifold vacuum and try that out....my timing is quite touchy. I have the stock electronic ignition that came with my 78 monarch and it only has one vacuum fitting. I dont have the spark control valve either. thanks for the help.
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Anonymous
Guest
Thor,
If you want to try to richen it up, you have to pop the top off the carb and looking at this diagram, http://www.geocities.com/mustang_man_19 ... _carb.html
To richen it up, Tighten the screw that is on the top of the metering rod assy. It in turn lifts the metering rod which in turn pulls the metering rod farther out of the metering rod jet.
On a very few of the YF's there is not a screw to richen it....there is just a tab that you have to bend.
You will probably tear the top gasket so have some thin gasket material on hand to cut another gasket. YF bowl gaskets are obsolete unless you get them with a rebuild kit.
I would tighten the screw in half turn increments, taking a test drive in between to see how its running. Dont tighten it more than 2-2.5 turns max! I would also check the float level while you have it apart just to double check that.
Also, please note where Ford has the vacuum advance hooked up on the carb
A thermactor equipped 6 is shown on this page http://www.geocities.com/mustang_man_19 ... e_six.html so you picked the right distributor. A thermactor was just a early smog control system...
Later,
Doug
If you want to try to richen it up, you have to pop the top off the carb and looking at this diagram, http://www.geocities.com/mustang_man_19 ... _carb.html
To richen it up, Tighten the screw that is on the top of the metering rod assy. It in turn lifts the metering rod which in turn pulls the metering rod farther out of the metering rod jet.
On a very few of the YF's there is not a screw to richen it....there is just a tab that you have to bend.
You will probably tear the top gasket so have some thin gasket material on hand to cut another gasket. YF bowl gaskets are obsolete unless you get them with a rebuild kit.
I would tighten the screw in half turn increments, taking a test drive in between to see how its running. Dont tighten it more than 2-2.5 turns max! I would also check the float level while you have it apart just to double check that.
Also, please note where Ford has the vacuum advance hooked up on the carb
A thermactor equipped 6 is shown on this page http://www.geocities.com/mustang_man_19 ... e_six.html so you picked the right distributor. A thermactor was just a early smog control system...
Later,
Doug
