Airflite40

I think I need to adjust the ignition timing, because when I start my car, it has no idle at all. It will run if I keep my foot on the gas, but will die otherwise. I know that I connect the timing light to #1, then I remove both vacuum hoses from the distributor, but how do I get it to 3000 rpm's? I just gotta use a helper? Once I check it, I know that I adjust it by turing the spark distributor, but which way will do what?

Garth S

Have you moved or removed the distributor? Timing settings are normally rock solid. I scribed a line on mine many years ago - and reinstall the distributor to that mark whenever it has been removed. The timing has never changed. There are a variety of things that could kill your idle, like an open vacuum line, oil fill cap, .....
Anyway, the 23 deg @ 3000rpm ( marked on the harmonic balancer) is the target. If you do not have a helper, look for an indication where the distributor had been bolted tight - and start there. This is usually in the middle of the range of the curved slot.
In on your own, move it 1/4" either way and restart - play around until it idles, then warm it up and set to spec.

GlenL

Sounds like bad vacuum advance. Either the lines or the diaphrams are leaking.

Get 3000 RPM? Reach under the manifold and open her up. I get the RPMs "by ear" also, the mechanical advance maxes out there so going to 3500 or 4000 doesn't change the timing.

Like Garth, I've got marks for where the distributor should be set. Running three more advance to get some extra ponies out of it. Engine still runs cool on the track. Tempgauge never gets to the second white line.

BrianG

Unless someone has been messing around with the timing, there's no reason for it to change. With electronic ignition there are no points to wear, and that's what used to make the timing drift, on older cars.
I'd look to the vacuum leak theory, or the idle valve if yours has it.

mark kibort

nahh, our cars idle fine with the vacuum disconnected. timing on the old cars are in the 8-10 dbtdc and without advance(vaccum) it goes to 20ish degrees.
(due to centrifugal advance)

if it isnt idling right, it could be due to a lot of things. leaks in the intake for one, spray with gum out or chemtool around the intake and see if it makes the idle raises. (ie idle leak sourse)

next, does it run full throttle well? if so, and its just an idle issue, you should be able to start testing stuff to see what the problem is. our cars should idle like champs. (even on 7 cylinders)

MK

GlenL

When stock, my car idled poorly with vacuum disconnected. Borys has the same engine.

mark kibort

why would it?? vacuum advance is not seeing any vacuum at idle that line is on the back side of the throttle plate and sees normal atomospheric pressure at idle speeds. put a light on your flywheel and disconnect the vacuum line, you will see no change in timing. you do get a very very slight change in false air as it not has a slight bypass around the AFM, but thats like opening up your mixture screw on the AFM. small changes dont do much there either (at least you cant hear anything change, although your emissions can change slightly)

mk

mark kibort

you may have a cold start valve that is not working. how does it run when its hot?
your euro is CIS, so it is slightly different than the AFM cars ive worked with, but the advance system is still close to the same, although you have a vacuum retard hose too. only remove the top vacuum line (vacuum advance) when you check the timing .

Mk

Airflite40

Thanks for the help guys. There was a mark on the distributor already, but it's almost all the way to the front (of car)

GlenL

No. No. No.

The advance line is not "ported" it is getting the manifold vacuum.

I've done this a dozen times. C'mon over, I'll show you.

mark kibort

Ok, im confused. so, the advance line on the side of the distrib, mounts to the intake and gets vacuum. this means, full advance (as far as the vacuum portion of it) at idle, and even more advance on decel. sounds backwards can you show me a picture of this?

Im trying to understand. Plus, i have a hard time understanding how the retard vacuum line works. I guess it works against advance by always having vacuum and it would pull back tiiming on decel and idle, but at full throttle it would have little vacuum. I think on scots 82 US, we just disconnected the bottom vacuum line to the distrib. advance was attached to the bottom portion of the throttle body, and on the head side of the throttle body, the vacuum line goes to the fuel regs. (they have vacuum and pull back pressure at idle, and release on part and full throttle)

mk

GlenL

Mark,

Can't find a pic or a reference, so I'll tell you what I know and what I think.

(Know) Pulling the advance hose at idle reduces the advance and the engine runs slow and rough.

(Know) Pulling the retard hose at idle doesn't do anything.

(Think) The advance hose, which attaches at the back, gets manifold vacuum from below the throttle plate.

(Think) The retard line gets vacuum from above the throttle plate.

(Think) As the throttle opens, the retard works against the advance to reduce vacuum advance while mechanical advance occurs.

(Think) This would allow the spark advance to follow the opening of the throttle better then just having advance and a stiffer spring. It take out some of the effect on manifold vacuum of engine RPM by using the pressure difference above and below the throttle and not just the manifold pressure alone.

G Man

IF I pull the vacuum line off the dist of my 84' I can feel no vacuum until I give it a little throttle. Is there some sort of valve that only allows vacuum to the dist above a certian rpm?

BrianG

Yes, Jim, there is a HUGE valve that controls this vacuum signal. It's actually the throttle body that performs this function. It's called "ported vacuum or timed vacuum" and it refers to the distribution or location of the vacuum source.

The "main" vacuum source is between the engine and the throttle plate (on the throttle body or the carb) and generally is taken right off of the intake manifold, somewhere. The "timed" vacuum source is taken from a port just barely ahead (on the air filter side) of the throttle plate so that it only "sees" vacuum when the throttle plate begins to open.

Hence, no vacuum at closed throttle........... max vacuum at partial throttle......decreasing toward...... nominal atmospheric pressure at WOT

G Man

Grasshopper says " thank you, oh wise one"