83 5.0 vacuum advance

[zac_f83]

need some schooling on the whole subject... what is factory base timing for 5.0? is it...

A. 10* BTDC (before top dead center)
B. TDC
C. 10* ATDC (after top dead center)
D. none of the above

i just about an hour ago made some marks on my balancer i can finally see..(TDC/ 5* ATDC/ 10* ATDC/ 15* ATDC)

it is currently at TDC no clue on total timing my guess is somewhere in the high 30s/ low 40s

here is what it does- has more power at full throttle until 3500-4000rpm then it falls on its face

engine bucking it down to a minimum but id like the vacuum advance to come in around 2200-2500rpm rather than basically off idle

i have been messing with the vacuum advance can also and currently have it in 3 turns(3 full right turns) WHAT i want to know is- does turning the can screw in(right turn) add or take how much it advances the timing?

if anyone local can come help me set this thing up for a afternoon that would be awesome

[JACook]

Base timing should be 10 degrees BTDC, with the vacuum advance disconnected. Also, total
timing, in the way it's normally stated, does not include vacuum advance, because vacuum
advance is only supposed to be there at part throttle.

[zac_f83]

ok well its at TDC right now and i just made more marks on my balancer and at idle with the vacuum advance connected it has like 15*

please elaborate more on what total timing is... only real experience i have with this stuff is my old 340 dart that didnt have vacuum advance as the cam didnt produce enough vacuum to need it... that was timed to 10* BTDC but it was all in at around 36* at like 2500-3000 rpms

[JACook]

Actually, it might be argued that an engine with a big cam needs vacuum advance the most,
at least on the street. The vacuum that is typically used for vacuum advance, does not
come from the intake manifold, it comes from a velocity port just above the throttle blades
when they're at idle. This ported vacuum will usually be low or nonexistent at idle, will peak
with about 7-10 degrees of throttle, and will be zero at WOT. Vacuum advance is not
controlled by RPM to any real degree.

The Mustang 4180C has a sort of hybrid ported vacuum that will show about 5-7" of vacuum
on the advance line at idle when the engine is warm. When the engine is cold, a ported
vacuum switch at the back of the intake will apply manifold vacuum, to assist with cold idle.

When checking base timing, or total advance, the vacuum line should be disconnected and
plugged. Your total advance should be in the ballpark of where it was on that Dart, or less,
depending on your cylinder heads and quench clearance. With a fast-burn chamber, such
as Twisted Wedge heads, a Ford Windsor will typically want closer to 32 degrees total.

Turning the adjustment screw clockwise normally decreases spring tension on the vacuum
advance unit. (More advance per inch of vacuum.)

[Bailey28]

Jeff,

I was reading your post above and was interested in the manifold to ported vacuum switch for the vacuum advance. I do not have any of the factory emission stuff but I would like to try the vacuum switch that supplies the manifold vacuum when the engine is cold, and switches to the ported source when the engine is warm.

I have seen the screw in type switches that install in the thermostat housing. I also have a cast iron thermostat housing (Stant) which has the threaded bung on top which will accept such a switch.

Can I order one for the 1983-85 GT or does something different control this function? Is there a switch for a different model Ford that you know of that can be mounted to the thermostat housing? Maybe around 140* or so would be helpful for the switch to ported

If you can help, (as always) I would appreciate it!!

[JACook]

The factory used a ported vacuum switch in the rear of the intake manifold, that switches
around 125-130F. Usually green. Motorcraft DY-173.

Putting one in the water outlet will work, but not as well. A ported vacuum switch that
is in the water outlet is usually meant to provide manifold vacuum to the advance when
the engine coolant is over 225F, to raise the idle speed and help cool the engine.

[Bailey28]

Ok, now I see the difference, however I don't have a rear water crossover on my Weiand 8124, and the front water crossover already has a mechanical temp and an electrical temp gauge connected to them. The only other place I could put something is in the thermostat housing.

[zac_f83]

Actually, it might be argued that an engine with a big cam needs vacuum advance the most,
at least on the street. The vacuum that is typically used for vacuum advance, does not
come from the intake manifold, it comes from a velocity port just above the throttle blades
when they're at idle. This ported vacuum will usually be low or nonexistent at idle, will peak
with about 7-10 degrees of throttle, and will be zero at WOT. Vacuum advance is not
controlled by RPM to any real degree.

The Mustang 4180C has a sort of hybrid ported vacuum that will show about 5-7" of vacuum
on the advance line at idle when the engine is warm. When the engine is cold, a ported
vacuum switch at the back of the intake will apply manifold vacuum, to assist with cold idle.

When checking base timing, or total advance, the vacuum line should be disconnected and
plugged. Your total advance should be in the ballpark of where it was on that Dart, or less,
depending on your cylinder heads and quench clearance. With a fast-burn chamber, such
as Twisted Wedge heads, a Ford Windsor will typically want closer to 32 degrees total.

Turning the adjustment screw clockwise normally decreases spring tension on the vacuum
advance unit. (More advance per inch of vacuum.)

ok so ive been turning it the wrong way? i have mine turned CW 4 turns... under WOT it falls on its face but if you ease into it dont miss a beat... i dont have a ported vacuum switch just the line coming off the front of the carb

if it wasnt raining id go find out what it has for total timing

[cb84capri]

yes. if you want to decrease vacuum advance turn it counter clockwise.

i don't have to ease into the throttle in my car at all..

cale

[zac_f83]

yes. if you want to decrease vacuum advance turn it counter clockwise.

i don't have to ease into the throttle in my car at all..

cale

ok then i must have to much vacuum advance

[zac_f83]

ok another problem.. when i slam on the brakes like say coming to a stop light the car will idle down to like 800 and then while im still stopping it dives to like 250 and it actually stalled on me today

[RickFury]

The factory used a ported vacuum switch in the rear of the intake manifold, that switches
around 125-130F. Usually green. Motorcraft DY-173.

Putting one in the water outlet will work, but not as well. A ported vacuum switch that
is in the water outlet is usually meant to provide manifold vacuum to the advance when
the engine coolant is over 225F, to raise the idle speed and help cool the engine.

I don't understand. What's the difference?

Why won't it "work as well" putting the green ported vacuum switch in the water outlet?

And why is it that a ported vacuum switch that is located in the water outlet is usually meant to provide manifold vacuum to the advance when the engine coolant is over 225?

[JACook]

A ported vacuum switch that's in the water outlet will only see actual coolant temperature when
the thermostat is open. A ported vacuum switch that's rated to switch at 125F-130F can't
do it's job as well when it's sitting on the other side of a device that opens at ~190F. A bleed
orifice in the thermostat would help, but it's just better to have it in constant contact with the
coolant inside the engine.

One possible solution is to use a heater hose elbow that has provision for an ECT sensor, and
put the PVS there. Fox HVAC systems do not have a valve that turns off coolant flow in the
heater loop, so a PVS there would work fine.

A PVS that is intended to raise idle speed when the engine cooant is over 225F can do it's job
when it's sitting on the other side of the thermostat, because at 225F, that thermostat had
better be open. It could also do it's job screwed into a manifold coolant passage, but what
to do if you don't have any of those ports available is probably why it's commonly found in
a water outlet. Those PVSs were in use back in '68, when manifolds had fewer places to put
one than they do now.

[RickFury]

Thanks for explaining that, JACook. If you said it, I knew it must be true, I just didn't quite understand why.

Is the purpose of the manifold vacuum to the vacuum advance when the engine is cold due to the fact that the carbureted Mustangs used a fully "electric" choke that comes off a bit too soon for emissions reasons, and not a thermostatic "hot air" choke that comes off slower as the engine heats up?

[Walking-Tall]

Thank you for linking me here, Sir xctasy, but six years later, I would LOVE to hear an answer that makes any realistic sense at all to the ^^^ above question. Sorry, but I've never found any requirement for a temperature-dependent vacuum switch, or sensor of any kind to be necessary between manifold vacuum and the distributor's vacuum advance to make an engine function acceptably when started and cold and then warming up...

[xctasy]

"Why won't it "work as well" putting the green ported vacuum switch in the water outlet?"


My answer is that the manifold VS to Ported VS interplay is the same one Ford has decided to use from the 1969 model year on its CA 351C's. Its just the way Ford did things around Here. 100% emissions sniffer test related, and to warm the engine up quicker. Two birds, one stone. Thermatic heat soak takes time to play between intake temperature and intake manifold or water neck temperate. Ford Australia didn't have the spaces for TVS valves like the rear crossover equipped 5.0 HO does.


You've got outside ambient temp, inside cooling water temp, manifold thermatic temp (different again)

14.4°C = 58°F (Dist-0-Vac)
18.3°C = 65°F (EST/TRSS)



Aussie 302C/351C 4V
35°C = 95°F
55°C = 131°F
107°C = 224.6°F

Both Red non manifold TVS switches are on the inlet water hose neck


http://vb.foureyedpride.com/showthre...83#post1838914

Dist-O-vac, (Distributor Modulator [Dist-0-Vac] System)
Electronic Spark Control System
Transmission Regulated Spark System


Same distorted quasi Load-o-matic philosophy.


Links were in the "Carb Tuning amp Drivability Need Some Guidance" post.

http://1bad6t.com/Maverick/repair/em...ntrols_02.html

&

http://1bad6t.com/Maverick/repair/em...ntrols_03.html

Ford's Aussie non catalyzed 79 to 85 Cleveland engines still copied the IMCO system, and used high ignition advance against a retard the peak advance when cold system. So under 65 deg F, its peak advance is locked out by some kind of wacko spark port advance like the old Load O matic.


That's just how they did it in the 83 5.0. Wacko, but Worko....


People have to see that the Spark Advance port is just like the old days of Autolite Load-o-Matics, with a new wrinkle...emissions reduction when cold. They did it on purpose to reduce idle emissions on higher compression engines, or where IIRC, NOx reduction was required due to engine design.


In the same way, Holley would (at Fords request)

1. reverse Idle an emissions era replacement carb, and

2. totally change the air bleed drillings and

3. Electric Bowel Vent drilling on the 4180C (Depending on who owned the patent, although it became a After market non Chevy sanctioned option through Holley's aftermarket supply for a few years).

4. EGR and Spark control port on 1984 passenger 5.0 HO carbs, and

5. the older Bowel Vent "power valve vacuum well is fed to the manifold through a restrictor and is also plumbed through the throttle shaft up to the top of the carb. The throttle shaft is drilled so that at full throttle it opens the power valve vacuum well to atmosphere. Again, this was done to prevent the manifold vacuum on a heavily loaded truck from closing the power valve at full throttle".

6. Four corner idle on the 5.0, not on the 460 4190c/4190ec. Look the same, but aren't.

7. Add annular discharge venturis or Economaster venturis or truck booster venturis (depending on who owned the patent).

With just a few hoses or a few changes, you can totally change the priority drilling and porting. Since Ford authorizes it, it can change it. Willy nilly to others, easy for Ford. Just like the side oiler block in the FE, or the hydraulic cam in the Falcon 170 verses solid cam in the 170 Bronco truck, Ford can change anything.

Same with wiring, Fords production expediency knows no bounds. Its easy when your making them, hard to follow when you have to service them....

I've said it before, but one wire different on an automatic trans earthing schedule for my 1998 Explorer XLT 4.0 means the difference between the overdrive working or not. Your not going to know until you attempt fitting another model year trans into it, and then discovering it won't work, and you have to go into another 18 hour drive-train pull out just to swap it over. That's modern production line. And it doesn't matter if your a race engineer doing the work, you don't know whatcha don't know. Same applies to the 1992 vs 1993 A4LD. Major bummer if you don't realize it.


That's why Ford always says things will always change without notice...even Tech Service Bulletins are in lag...

[erratic50]

If your timing marks are questionable there are ways to tune without

some guys use interference in the spark plug hole and barring over the engine to approximate TDC pretty closely and this works well.

You may want to just check the weight of the mechanical advance vs springs and make sure things work correctly and tune by ear.

tuning by ear goes like this

- warm up the car
- turn it off
- disconnect the vac advance temporarily
- loosen the holddown tab on the distributor
- start the car
- turn the distributor until the motor just starts to slow down
- while looking at where your dizzy is (relative to the hold down) advance until the motor just starts to speed up then back just a little.
- turn off
- tighten down
- reconnect the advance
- try to start it

if the car kicks against the starter and cranks hard it's just a little too advanced. If it doesn't repeat until you find this spot then back it off.

This will find where your motor likes to have the base timing set.

now check how many degrees advance you see on the light when you rev it up. You don't want more than about 38-40 degrees total including base advance generally. That means you want to see about 25 degrees of vac plus mechanical

listen for signs of detonation or pinging, back off advance accordingly

good luck !!

[ashley roachclip]

I use a vacuum gauge, and with the vacuum advance disconnected and plugged , I set the idle as low as it will run smoothly.
Then looking at the vac. Gauge , I aim for the most vacuum I can get , then back the timing off 2 inches of vacuum .

[JACook]

Thank you for linking me here, Sir xctasy, but six years later, I would LOVE to hear an answer that makes any realistic sense at all to the ^^^ above question. Sorry, but I've never found any requirement for a temperature-dependent vacuum switch, or sensor of any kind to be necessary between manifold vacuum and the distributor's vacuum advance to make an engine function acceptably when started and cold and then warming up...

In the Fox Mustangs, the reason manifold vacuum was applied to the distributor when the engine is cold,
is because of the rapid electric choke opening rate these cars had. During the period when the choke has
just come all the way open, and the idle has dropped off the fast idle cam, manifold vacuum is routed to
the distributor, to raise the idle speed a couple hundred RPM, and to aid part-throttle driveability until the
engine is closer to normal operating temperature.

I have found this to be a useful strategy on some non-emissions engines as well, from time to time.