so, i posted that the idle issues with my truck are over. there was something clogging the main jet - one or both.
this brings up another thing. now that it's running right, i figured i'd double check the timing, dwell....etc.
i hooked up the diagnostic tool, made sure the dwell, points gap, rpm were all correct. dwell at 31, points gap at .017, rpm at 650...........when i hooked up the vacuum gauge, it reads late ignition timing. i can't seem to get it to move from that reading.
i blocked off the vacuum advance and set the timing where it idles best.....about 10 degrees btdc. also, i turned the screws at the base of the carb in and out to get the highest vacuum reading. the left screw (pass. side) turned all of the way in will make the truck stumble. however, the right side had no effect at all.....in or out. i wonder why.
so, why won't that screw affect vacuum?
and why can't i get the vacuum gauge to read in the green? it reads late ignition timing?
any ideas?

 

Is your vacuum gauge factory? I would try hooking up another gauge and see what the vac is reading.

 

How many inches of vacuum is the gauge reading? Is it steady or pulsating?

Also, you definitely have a problem with the right-side idle screw & passage if it has no effect on the vacuum reading or the idle! Sounds like you're only idling on the left-side circuit.

 

the gauge is not factory. it's new, purchased a few weeks ago.
i have to check on how many inches it is reading. i'm just guessing (but, i will verify) that it is right about 19 inches. i think on that gauge the "normal" reading is 20 to 22 inches.
definitely not pulsating. holds steady.
yeah...that right side idle circuit has me puzzled. because the left side reacts fairly quickly when i turn the screw. the wierd thing is: it does idle and respond very well.

 

When you start a thread like this you need to say exactly what you have, engine, carb etc.
If you look in your shop manual the normal idle vacuum for a stock 352 at normal operating temp is 18 inches with 6 degrees initial timing at 550-575 idle rpm.
Providing you haven't over tightened the mixture screws and ruined the seat, if there is no response from one of the screws you likely still have something restricting the Idle and transition circuit. These are very small passages and are easily blocked.
You can sometimes clear a small restriction in that circuit by removing the idle mixture screw and spraying some carb cleaner into the idle air bleed. You should get some fuel and cleaner out of the idle screw hole.
You want the idle screws to be from 1 to 1-1/2 turns out if they are less then 1 turn out it can cause an off idle bog because that circuit also feeds fuel to the transition circuit.

 

[QUOTE=Crop Duster;21224362]When you start a thread like this you need to say exactly what you have, engine, carb etc.


you're absolutely right, crop duster. i totally forgot to do that. i apologize for that.
so, yeah...352 2bbl, 4 speed.
i can tell you that i've never bottomed out either screw, plus i've checked the seats. they're both like new. i was thinking of spraying carb cleaner into that hole to see if it'll change things if this rain stops, i'll get out and do that. they're both set at 1 1/2 turns out. it seems to like it there.
if 18 inches of vacuum is normal, i believe that's about where i'm at. but the gauge does read late ignition timing around that spot. like i said, the needle doesn't flucuate or bounce. i think that's a good sign.

 

Ignore everything on that gauge except the numbers, whoever made that gauge has no idea of what engine you have or what the timing should be.
In my experience if you set the timing on an engine using a vacuum gauge you will get it to far advanced every time.

 

Lol....done. makes perfect sense to me.

 

well, i finally got outside to troubleshoot this truck again. i'm glad i did.
first of all, the vacuum gauge indicates that 17 - 22 inches is a "normal" motor. i will ignore the markings and just shoot for at least 17 inches.
i removed the drivers side idle mixture screw and blew some carb cleaner into the hole. no change when i reinstalled the screw. then i charged up the 6 gallon compressor, put a rubber tip in the nozzle and blew air through it. reinstalled the screw and the vacuum immediately went from about 13 inches to 17 inches. i did the same to the passenger side screw. the vacuum stayed at 17.
so, i now have as close to a factory feel as i ever had. this truck runs really nice (before these issues came up). but i always felt like it was about 95% if you know what i mean.
now, it does, in fact, feel perfect. throttle response is crisp, as it should be. i'm actually surprised at the amount of torque this motor puts out. i can catch rubber in 2nd gear easily.
ok, guys....thank you for the input. i really appreciate the brainstorming and the help.

 

When the carb is in great shape you will find the you don't move too far from the initial 1 1/2 turns outward. Once there I can get my 390-2V to 20" of vacuum at idle by tweaking the distributor. The distributor will give you more leeway so advance it slowly and watch for the peak closely. Once there I dial mine back about 1 degree, with today's gas, and then take a drive on the freeway to listen. To get far more in depth one can pull the distributor and take off the plate to see the advance springs inside and see where they are set. Varies from distributor depending on application. Once you know that then you can see what your total mechanical advance will be when adding what the springs say plus your initial.

As an example and why Ford did this from the factory is beyond me. The 68 Cougar I have was bought from the dealer, by my father, so never tampered with. Ford set mechanical advance at 10L or 20 degrees. Initial was typical Ford of 6 BTDC. giving a total of 26 degrees. The engine should have been around 34-36 total degrees. The car got crappy gas mileage of around 12-13 mpg for a 302-4V. Not till years later did I then know enough to play with a distributor. Since I now had a cam with more duration it made sense to leave it at 10L and move the initial to 15 degrees for a total of 35 now. What a difference! Plus mileage at 17 mpg now. Most likely a 352 has a 13L and 18L plate inside and is set at 13L for 26 degrees mechanical.

 

i just started it again and fussed with the distributor. i advanced it and now i have a pulsation free 18 inches of vacuum. i forgot to mess with it after the carb results.
it bucked against the starter just a bit so i backed it off til it no longer did it.
well, this is where my 50 plus years of shade tree mechanics still shows my inexperience - i know nothing about initial advance, total advance, and how or why to change it. i really never took the time to understand it as i should have.

 

Do you have a dial back timing light with a tach? If you do you can check the curve in the distributor. The shop manual has the specifications for the stock distributor but be aware the rpm and advance numbers for the centrifugal advance are for use on a distributor machine. To check it on a running engine you have to double the numbers because the distributor is only turning 1/2 the crank rpm.
My 65 manual shows a maximum advance of 28 degrees at the crank at 4000 engine rpm for a 352. You add the initial to that for the total. Most Ford engines are happy with 34-36 total. My guess is if your distributor is stock and still working as advertised 10 initial is about your limit.

 

sounds waaay easy. but my timing isn't a dial back. timing lights are basically dinosaurs but 'm gonna ask and see if someone i know might have one. your instructions sound simple enough that even i could do it.