Questions on adjusting Timing

[cobra3073]

Joe,

This is a LITTLE bit off topic but I want to take advantage of what I see as a "teachable moment."

One of the MAJOR thing I believe we are striving for on this site is our being dead set against flaming or making other members uncomfortable to the point that they are reluctant to post. I assure you that as long as I am a Moderator, this type of stuff will not be tolerated. I see shop manuals as a guide or a good starting point - - they are not necessarily the only way to get a job done.

If you (or anyone else) has a certain way or different approach towards an issue relevant to a thread, please do not hesitate to bring it forward. The individual members can make the decision to try it or not.

Again, this is a bit off topic but I wanted to bring forth the point sooner rather than later.

THANKS for giving me the opportunity to address it!

BT

 

[73vertproject]

The fact that your idle increased when you hooked up the vacuum advance indicates that your vacuum lines are not in the original configuration. There should be no vacuum present at idle, as the advance should be connected to ported vacuum on the carb. That being said, many experience better performance running the advance off straight manifold vacuum, which is how I have it set up on my '65, and plan on doing on my '72 soon. It sounds like that is how yours is already configured. I know how I time it set up like this, but I won't go into it, simply because I don't feel like having to defend my methods when other posters disagree. Any deviation from the Shop Manual always seems to spark a heated debate (at least this is my experience on other forums).

Hi Joe -

It is my sincere belief that the members of this forum not only "tolerate" but actually encourage individualism when it comes to modifying our cars. I, for one, would sure like to hear how you time and tune your motor, because it may be useful to me down the road. I say share your experiences and ideas, and if some people disagree, I believe they'll do it respectfully. You should not feel like you have to defend anything. That's how we do things around here, anyway.

Doc

 

[f117rt]

OK, Back to the Timing/Idle question.

THis manual is driving up the wall!

The manual says to have the lights ON and carin in DRIVE while adjusting the idle. to 600rpm

When timing is set I am assuming that the car is now in PARK and I will need to adjust the idle DOWN to 600 again since when you place the car in park the idle will rise.

1. Remove the vacuum from the distributor and plug up the hose

2. Adjust timing to 0 (TDC)

3. Bring idle to 600 again

4. Adjust timing and idle until I reach 10 deg advance at 600 rpm.

5. re-connect vacuum to distributor ( at this point what should happen? should the idle increase or decrease?

Is my procedure correct or am I doing somthing wrong?

Thanks

 

[Joe]

Using the factory hose routing for vacuum lines, the idle should not change at all when you hook up the vacuum line to the distributor. This is because the distributor uses ported vacuum from the carburetor for advance.

Ported vacuum is when the vacuum source is a port inside one of the primary venturis. It is physically located above the throttle plate position at idle. Because of this, there is no vacuum present at idle. Once the throttle plates are advanced past idle, they move above the port inside the venturi, exposing it to manifold vacuum for advance.

The whole purpose of using ported vacuum instead of manifold vacuum is to reduce emissions at idle. Because your idle speed increases when you hook the vacuum advance line back up, it sounds as if your vacuum advance line is connected directly to manifold vacuum. As I said before, many, myself included, get better performance this way in the form of a much smoother and more powerful idle.

I run my '65 advance this way. If I connect it to ported vacuum, the idle is very rough and I have to increase the idle speed to keep it from stalling out in gear. It is set at 9* BTDC, never pings, and is very smooth. I plan on trying this on my '72 sometime soon.

 

[Joe]

I hate to post twice in a row, but I thought of more stuff. You say that right now you are at 10* BTDC. That seems just a bit high to me, but every engine is different. What I would do is to hook the vacuum advance line back up, and then reduce the idle speed back down to where you want it using the idle speed adjustment screw only at first, then fine-tuning the mixture screws if necessary. If it still fluctuates, though, you might try retarding the timing a degree or two. Once you have it idling where you want it and (hopefully) not fluctuating... ROAD TEST! If it runs satisfactorily, you are good to go. If you are like me, though, you will continue to fool with it until it runs worse, then put it back where it ran best. I have to use a vacuum gauge and tach to time mine, as the harmonic balancer slipped a long time (at least 17 years) ago.

 

[f117rt]

I hate to post twice in a row, but I thought of more stuff. You say that right now you are at 10* BTDC. That seems just a bit high to me, but every engine is different. What I would do is to hook the vacuum advance line back up, and then reduce the idle speed back down to where you want it using the idle speed adjustment screw only at first, then fine-tuning the mixture screws if necessary. If it still fluctuates, though, you might try retarding the timing a degree or two. Once you have it idling where you want it and (hopefully) not fluctuating... ROAD TEST! If it runs satisfactorily, you are good to go. If you are like me, though, you will continue to fool with it until it runs worse, then put it back where it ran best. I have to use a vacuum gauge and tach to time mine, as the harmonic balancer slipped a long time (at least 17 years) ago.

What do you mean by Harmonic balancer slipped?

I am have a problem now that I can't see the timing.

No matter which way that I turn the distributor I can't read the timing.

Anyone have any ideas why I can't read the timing?

Timing light is connected to #1 plug wire, idle set to 600 and dist vucuum line unplugged and plugged.

I would hate to take it to a shop if I am doing somthing stupid.


The harmonic balalancer Has the timing markings correct?

With the engine Off, can you turn it by hand?

 

[machman_73]

My harmonic balancer also slipped. The balancer is made up of an outer ring with timing marks on it. Then a rubber seal and inner hub.

The rubber drys out and causes the outer ring to slip moving your timing marks way out wack. You need to get the engine on TDC and see where your timing marks are. I think I used a 1 inch deep well socket and long racket to turn the crank. MAB

 

[72HCODE]

is the timing light actually firing?

even if the balancer slipped it should read something unless the thing slipped 180 degrees and the light is firing on the balancer with no timing marks.

or did the marks sticker fall off?

lets assume worst case scenario, your balancer slipped and now you have no idea the timing, but the engine is running.

First disconnect and plug off the vacuum advance. you just want to run on mechanical advance.

now you can vacuum tune the engine.

Bring the idle screw down so the engine is just about to stall but running steady. The reason you do this when you set ignition timing is to make sure 100% that the mechanical advance is NOT coming on at all.

hook up your tach so you can see the rpms.

next install a Vacuum gauge on full manifold vacuum, NOT ported vacuum.

What you do now is Tune for Max vacuum reading.

Here is the tricky part. As you advance the timing the Rpms will go up and the Vacuum will go up. You have to keep adjusting the idle rpms to remain constant with the rpms you set when you first started. So if you started at 525rpms, then you must maintain that rpm as you adjust the distributor and watch the vacuum gauge for the highest reading.

Remember you advance the distributor and vacuum will go up, because rpm is going up, so always reset the rpms back down, so you can compare one reading to the next.

So lets say after you fart around with the distributor for 20 minutes you find your highest reading at 525rpms is like 14HG, now you back off the distributor 1-2 HG.

lock the distributor down. Reset Idle rpms to Spec, i find spec can be too low for some engines 650rpm is a good range.

Remember to set the idle rpms with the headlights on, and the car in gear with somebody inside on the brake, you have to set the idle rpms under transmission load and electrical load.

Ok now your ready for test #1.

shutdown the motor, wait 1-2 minutes, and try to start it again. This will test for a hot start problem, if the engine will not fire, then you will need to retard the distributor slightly. even though you just went through all that you will have to compensate for the ability of the starter to actually start the engine when its hot.

Now if you shutdown the engine, and she keeps on trying to run, that is called dieseling, that means you need to retard the timing slightly.

Test #2 go for a drive, with the vacuum advance still disconnected you will need to drive the car, look for a really huge long straight hill, and punch it up the hill.

you will need to listen for a notable change in the exhaust tone, if you hear marbles rolling around in a metal tube, back off the throttle and head for home your engine is pinging and you will need to retard timing slightly. keep going back and forth from the garage to the road until the pinging stops. if the car starts to hesitate that could be another problem with the fuel system. if advancing the timing makes the hesitation go away but the pinging starts then you have to start looking at the carburator for problems or the mechanical advance for problems.

if the pinging never stops that is a lean condition and you could have other problems with the ignition system.

ok so now your car isn't pinging, and its not hesitating. Time to hook up the vacuum advance. if you have a tunable vacuum advance great! if not don't worry yet.

go for a drive check for pinging. if you have none, and you have an adjustable vacuum advance then you can keep tuning in more and more vacuum advance timing until she pings then back off 1-2 turns. if you don't have a adjustable vacuum advance then you run what you broung.

So that is how you would set timing using a vacuum gauge.

if your balancer slipped then you will need somebody to fix it, because its involved, you have to take most of the stuff off the front of the engine, pull the rad fan and belts.

pull the valve covers, pull the #1 plug. pull the crank pulley. then you need a piston depth gauge and refinance the Valves opening and closing, and i think a degree wheel, to figure out the position of the new balancer on the engine and set TDC again.

as you can see vacuum tuning the ignition timing is a tedious balance between different conditions somewhere in the middle is your sweet spot and the engine runs the best at that ignition timing.

its more scientific when you have a metered gauge telling you where you are but even after setting timing to an exact point you find you need to bump it here and there a little.

like the manual says 6 BTDC for inital but you find it better at 12 BTDC or another person likes 18 BTDC.

 

[f117rt]

Is replacing the Harmonic balancer difficult?

What is the precedure?

Anyone have a link on how to do this?

 

[72HCODE]

well you have to take pretty much everything off the front of the engine just to get to the balancer.

you have to get the rad out, you may need to remove the a/c condenser.

then you need to take the front of the engine apart, fan comes off belts, pulleys,

unbolt the main crankshaft bolt that is in the center of the balancer

your most likely going to need a harmonic balancer puller.

then you need to check the new balancer and it should be keyed like the original. Then depending on the balancer you may need to heat it up its tight fit to get one on.

so people boil the balancer for 30 minutes in water. then with heavy gloves you take it over to the engine and line it up and push it on(not easy)

then you torque down the crankshaft bolt to spec, and put everything back together.

if everything goes right you can do it over a weekend.

 

[f117rt]

well you have to take pretty much everything off the front of the engine just to get to the balancer.

you have to get the rad out, you may need to remove the a/c condenser.

then you need to take the front of the engine apart, fan comes off belts, pulleys,

unbolt the main crankshaft bolt that is in the center of the balancer

your most likely going to need a harmonic balancer puller.

then you need to check the new balancer and it should be keyed like the original. Then depending on the balancer you may need to heat it up its tight fit to get one on.

so people boil the balancer for 30 minutes in water. then with heavy gloves you take it over to the engine and line it up and push it on(not easy)

then you torque down the crankshaft bolt to spec, and put everything back together.

if everything goes right you can do it over a weekend.

I guess for now i'll be doing the "vacuum method" for setting the timing!

 

[72HCODE]

Really make sure that it has slipped, check that 1 is firing , maybe try another timing light to confirm.

Check your ignition wires make sure the firing order is correct.

Check the balancer does it still have the timing marks on it?

See if the outter ring on the balancer really is moving, try turning it by hand.

You could plug in a compression tester gauge, bump the starter so the piston in on the compression stroke and see if you get a high reading when the timing marks get close to 0

You could also turn the crank by hand with a breaker bar and check with a gauge or a piston depth gauge, just to make sure you really have a balanacer that slipped.

Could also see if the engine jumped the timing chain a few teeth.