Timing Light and other Qs

[RainMoore]

Hello all,

Just got my first timing light to use on my 74' 2002 Automatic, and I've got some questions.

Finally got the thing running after some rewiring and replacing the points and condenser. Haven't checked the actual 'quality' of the spark, need an extra set of hands for that. The engine is running somewhat smoothly just by trial and error, turning the dizzy and messing with the main mixture screw and idle screw (its a weber 32/36). I've read to start out at 2 full turns out but its happier at 1-1.5 turns (which would mean it likes a lean mixture, right? I'm at 7,500 ft by the way).

 

Trying to set it to manufacturer recommendation, but it doesn't idle well below 950 (recommended is 900 -/+ 50), and the idle rpms fluctuate within a range of about 50-75 constantly, so somethings not working smoothly here.

Also, once I hooked up the light I found it was idling best at 0 degrees advance, and every time I tried to set it to 25 degrees advance it dies. 

 

First time for all of this, so I'm assuming I'm using the light correctly. Found that I had, by ear, set the timing pretty much dead on at 0 degrees advance. The little metal ball is easily seen, though it fluctuates as though the timing wanes in and out of being correct, is this normal?? The idle doesn't sounds particularly "even" but I don't have a trained ear for this so maybe its fine.

Dwell is at 60-62, point gap at 0.016, and voltage on the light meter across the battery terminals is reading about 13.9 V.

 

Also after running for a while, the coil is quite hot. Didn't burn me but couldn't touch it for more than a couple seconds. I don't know much yet but I know that can be a bad sign. I had run a wire from the starter motor to the + on the coil as per the universal schematic on this site, but just noticed that specifically on the automatic schematics there isn't one. Just the green wire from the fuse box and starter switch. So I've disconnected it and will see what's what tomorrow. Could it be getting too much voltage while running?

Its a Bosch Blue coil, which I understand has a resistor built into the coil itself, tho I've read a lot of confusing advice suggesting there is supposed to be a small resistor in the green wire somewhere, which there definitely isn't now.

 

Note that the points I first found in the car were burnt and pitted pretty badly.

 

The PO told me it had developed a problem where after running for a while it would sometimes falter and die when stopped at a light, guess no one could figure out what the problem was.

 

On a side note, tried to pull the car outside to run it and let the gas treatment do its thing (lots of gunk on the plugs) and the gear shifter doesn't seem to be functioning...forward or reverse does nothing when I push the gas. It does allow me to roll it by pushing tho. Any ideas on where to start with that? I know most of you have sticks...

Found a terminal underneath the body, around the middle where the gear shift is, which has two green/white wires which have been cut and are just hanging there. Cant figure out what those are. Is there any part of the shifter that's electronic or is it all mechanical?

 

Thanks!

['76mintgrün'02]

Congratulations.  That is a nice timing light and it is going to teach you a lot about timing and how your distributor is performing.  

 

1.5 turns out on the idle mixture screw is okay, but the fluctuating idle may be due to it running too lean.  Mine starts to do that if I am up over 13 on the AFR gauge and it is smoothest down around 12.25-12.5ish.  Without an AFR gauge, you just follow the Weber "best lean idle" instructions; but before messing with the carburetor, you need to get the dwell and timing set. 

 

Dwell first and then timing, followed by idle mixture/speed.

 

Your dwell reading should be steady and at the low end of the 59-64 range.  (as the points wear, the number tends to rise, due to the little rubbing block wearing down).  I use 60 because it is a nice round number, but 62 is fine also.  Saying it is set at 60-62 makes it sound like it might be fluctuating.  Hopefully not. 

 

Once the dwell is set, you move on to timing.  Changing the dwell changes the timing, since the degrees of rotation that they're closed (dwell angle) affects when they open (fire the spark) and that is the event described by "timing".  You are setting the spark to give time for the gas to ignite and push the piston down.  Too much advance and it pushes down on the piston while it is still coming up and that is pre-ignition, or pinging, or pinking, etc.  That's what you want to avoid.

 

The BB that you see on the flywheel is 25 degrees before top dead center.  TDC is marked by a thin line stamped in the flywheel and the letters OT.  (It is to the passenger's side of the BB on the flywheel).  It can be hard to see, so it may be helpful to clean that area off and carefully put some paint in that line with the tip of a bamboo skewer or something.  (If you use the search feature, you'll find some nice photos in the archives, where guys like Ed have painted theirs).

 

If you are seeing the BB with the light's advance feature set to zero, you have 25 degrees of advance at idle.  Mine runs well over about six degrees and is set at nine degrees now.  It would tolerate more, but doesn't seem to need it.

 

To see where yours is idling, you need to press the "function" button on the light until you see zeros on the left side of the screen with the light flashing.  Then you can use the up/down arrows to advance/retard the light.  Point the light down the hole and bump the up arrow and see how high you have to go until you see the OT line.  That will be the amount of advance at idle.  From what you've described, it might be 25 degrees.  (which is too much).

 

Once you see the line, rev the engine and let it drop back down, to see if the line comes back to the same place.  Dirty old distributors can get sticky and not come back to "zero".  Then, you'll be chasing your tail trying to set the timing.

 

This is a thick topic.  My fingers are tired.

Tom

 

 

[RainMoore]

Wow ok, I thought the BB was zero. This makes more sense now. I’ve already run the light from 0-25 while looking at the flywheel, but didn’t know what I was looking for.

With the advance screen on, at 0 degrees I see the BB. That seems to be where it’s running best.

I misspoke about the dwell, I don’t think it’s fluctuating. Just the rpms and the steadiness of the BB. It’s dead center then vanishes for a moment then reappears.

I read another post which described this as “hunting”, and like that example the idling isn’t consistent, so I think I’m still a little off. It sort of surges and abates. Lots of inconsistent shaking of the engine block.

 

I’ll try your idea tomorrow. Thanks once again for the super clear breakdown. You’re right, this is complicated stuff to explain.

[dlacey]

The timing ball on the flywheel is to set the timing at a certain RPM, given in the manual depending on spec/ model year. Usually something like 2700rpm.

The logic is that timing at the top of the rev range, when the centrifugal advance is well activated, is a lot more critical to performance. The timing at idle revs can be anywhere in the 2-12 Deg BTDC , doesn't really matter in terms of starting/idling.

 

By what you describe your static timing is well advanced...now you have the light, set it to zero, get a friend to hold revs at 2xxx RPM and twist dizzy so you can see your ball with the light. This all assumes the dizzy is working somewhat how Bosch intended and is not completely worn out or rusted solid.

['76mintgrün'02]

Based on a photo you provided in another thread, you have the 'early style' distributor with smaller springs than the 'late style.'  Those springs rub against lobes on the underside of the center post and that wears flat spots on the sides of the springs, which weakens them.  There are other contact points within that mechanism that wear down and add slop to the equation; so the puny springs are not working with the geometry they were designed for.  Add dirt or corrosion to the equation and things get pretty funky in there.

 

I could type until breakfast about how these things wear, but it'd still leave a lot to your imagination, since you have yet to take one apart.  I'd still like to discuss it though.

 

You have the vacuum line to the distributor disconnected and capped at the carb, right?  You don't want to use the vacuum retard feature.  That was smog stuff.

 

When you see the timing marks on the flywheel moving, even though the rpms are constant, that is visible evidence of slop in the mechanism.  One of the most consistent problems is that play develops axially (up and down) in the shaft and because the gear that drives it has skewed teeth, that up and down motion translates to rotational motion, which translates to timing variation.  To gauge the wear, you remove the distributor and measure between the gear and body.  The center post is not part of the shaft, so pulling up on it is misleading.

 

 

There are (or were) two fiber washers on the shaft, with one between the gear and the body of the distributor and the other one up inside the body.  They both tend to wear thinner, but the one inside often tends to crumble, leaving .035" of play.  That is a problem, because it will  not give steady timing, which will not give a steady idle.  That one is pretty easy to fix though, with a couple mail order washers.  

 

Parts for these things are not easy to come by, aside from those washers.

 

Now that you have the proper tool for the job, you can pull that distributor out and inspect it, to see what you're working with.  That $110 timing light just bought you HOURS of fun... but be careful.  Distributors can be hobby forming.

 

Tom

Edited April 25, 2021 by '76mintgrün'02
added photo

['76mintgrün'02]

Here's a link that'll show you what's inside the distributor and where some of the wear happens.  Making them function "like new" again would be quite challenging, but cleaning and shimming and lubing might keep yours in service.  Hopefully.

 

 

Tom

['76mintgrün'02]

11 hours ago, RainMoore said:

Its a Bosch Blue coil, which I understand has a resistor built into the coil itself, tho I've read a lot of confusing advice suggesting there is supposed to be a small resistor in the green wire somewhere, which there definitely isn't now.

 

Here is a little reading about Blue coils. 

 

https://www.ratwell.com/technical/BlueCoil.html

 

Most have built in resistance, but apparently not ALL of them.  Yours was lower than 3 ohms when you measured it, which is why I suggested checking the number stamped in the bottom of your coil in a previous thread.  Part of the problem of starting multiple threads on the 'same topic' is that useful info/photos are left behind. 

 

When in doubt, add photos to posts.  They add information and entertainment value.  Also add information about what model year you are working on, since things like inline resistor wires are different between '74 and '75-'76 cars and early cars have the resistor block... and stuff.

 

11 hours ago, RainMoore said:

Note that the points I first found in the car were burnt and pitted pretty badly.

 

The PO told me it had developed a problem where after running for a while it would sometimes falter and die when stopped at a light, guess no one could figure out what the problem was.

 

A faulty condenser can do that.  It can also cause pitted points.

 

 

Using the light to measure advance at idle is a good exercise for getting familiar with the light and the process.  Using the BB to set the timing is what's recommended with a basic timing light that does not have built in advance capabilities.  You are now empowered.

 

One of the most important things to consider when setting timing is the total, or all-in advance that the distributor is giving.  Too much advance and you can get pinging, which will damage the engine.

 

A safe number to start with is 36 degrees, so setting it there and then seeing what that leaves at idle is a good way to set the timing.  To do that, bump the variable advance up on the light to 11 degrees and shine it down the hole, while revving the engine to 3k rpm and rotate the distributor until you see the BB.  Then rev a little higher to make sure it does not continue to advance.  That'll be 36 degrees all-in.  Once that's set, let it drop to idle (hopefully it still will) and drop the advance on the light to find the OT line and see how much advance that leaves.

 

Pinging sounds like a slight metallic tapping noise and usually happens when you mash the pedal to the floor.  You need to listen carefully for that while on your test drives.  It's harder to hear at higher rpms, due to engine noise.  Mine was doing it when mashing the pedal between 2k-3k rpm, which is basically bogging the engine, which we know better than to do... but you still want to eliminate that 'feature' with less advance.

 

There should be a tutorial on the FAQ with general instructions/tips for variable advance lights.  Maybe I'll copy/paste some of this stuff into one some day.

 

One last tip before I get on with my day.  When using the variable advance I find it much more pleasant to set the number on the light and then rev until you see the mark and note the rpm, than it is to set the rpm and hunt with the buttons on the light.  You spend way less time with the engine revved up and your neighbors will thank you.  Also, wear ear protection while doing this.  Your ears will thank you.

 

Tom

[Hans]

38 minutes ago, '76mintgrün'02 said:

 

Here is a little reading about Blue coils. 

 

https://www.ratwell.com/technical/BlueCoil.html

 

Most have built in resistance, but apparently not ALL of them.  Yours was lower than 3 ohms when you measured it, which is why I suggested checking the number stamped in the bottom of your coil in a previous thread.  Part of the problem of starting multiple threads on the 'same topic' is that useful info/photos are left behind. 

 

When in doubt, add photos to posts.  They add information and entertainment value.  Also add information about what model year you are working on, since things like inline resistor wires are different between '74 and '75-'76 cars and early cars have the resistor block... and stuff.

 

 

A faulty condenser can do that.  It can also cause pitted points.

 

 

Using the light to measure advance at idle is a good exercise for getting familiar with the light and the process.  Using the BB to set the timing is what's recommended with a basic timing light that does not have built in advance capabilities.  You are now empowered.

 

One of the most important things to consider when setting timing is the total, or all-in advance that the distributor is giving.  Too much advance and you can get pinging, which will damage the engine.

 

A safe number to start with is 36 degrees, so setting it there and then seeing what that leaves at idle is a good way to set the timing.  To do that, bump the variable advance up on the light to 11 degrees and shine it down the hole, while revving the engine to 3k rpm and rotate the distributor until you see the BB.  Then rev a little higher to make sure it does not continue to advance.  That'll be 36 degrees all-in.  Once that's set, let it drop to idle (hopefully it still will) and drop the advance on the light to find the OT line and see how much advance that leaves.

 

Pinging sounds like a slight metallic tapping noise and usually happens when you mash the pedal to the floor.  You need to listen carefully for that while on your test drives.  It's harder to hear at higher rpms, due to engine noise.  Mine was doing it when mashing the pedal between 2k-3k rpm, which is basically bogging the engine, which we know better than to do... but you still want to eliminate that 'feature' with less advance.

 

There should be a tutorial on the FAQ with general instructions/tips for variable advance lights.  Maybe I'll copy/paste some of this stuff into one some day.

 

One last tip before I get on with my day.  When using the variable advance I find it much more pleasant to set the number on the light and then rev until you see the mark and note the rpm, than it is to set the rpm and hunt with the buttons on the light.  You spend way less time with the engine revved up and your neighbors will thank you.  Also, wear ear protection while doing this.  Your ears will thank you.

 

Tom

How do you get the 11? 

['76mintgrün'02]

Mathematics!

 

The BB is 25 degrees BTDC, so adding 11 degrees to that gives a total of 36.

 

You could also bump the light up to 36 degrees and use the OT line.

[Hans]

22 minutes ago, '76mintgrün'02 said:

Mathematics!

 

The BB is 25 degrees BTDC, so adding 11 degrees to that gives a total of 36.

 

You could also bump the light up to 36 degrees and use the OT line.

I think OT plus 36 is easier. Thanks for lengthy explanation.

['76mintgrün'02]

19 minutes ago, Hans said:

I think OT plus 36 is easier.

 

Thanks for sharing your preference.  There are so many ways to approach this stuff.  

 

On my flywheel, the BB is easier to see than the line and using it saves me fifty clicks of the little button.

 

Imagine how cool it would be if they'd stamped degree lines in the edge of the flywheel, instead of just the two marks.  Then, a basic timing light would be enough to really psyche out the advance situation.

 

Another timing light exercise/equation is to figure out how many degrees of advance the distributor puts out.  It's also fun to see at what rpm it starts to come in and where it stops.  Put those points on a graph and you've got the start of a timing chart.  

 

 

 

 

Tom

Edited April 25, 2021 by '76mintgrün'02

[John76]

2 hours ago, '76mintgrün'02 said:

Imagine how cool it would be if they'd stamped degree lines in the edge of the flywheel, instead of just the two marks.

Always wondered why the TDC line is stamped OT....does this mean "on top" ??

Just stamp the flywheel  TDC with "AA" to be consistent with the "BB" (25 deg.), and follow with a "CC" (total advance).

[Son of Marty]

In German top dead center is oberer totpunkt so OT. But on top is a good way to remember it.

[Mark92131]

What are the last 3 digits on the distributor you are running in your 74 Automatic. "003"?  Each distributor model has a unique advance curve, so knowing what advance curve you should have vs what you actually have can indicate issues like sticky advance plates and worn springs, etc.  According to the blue book, your 74 USA Automatic should be timed to 25 degrees BTDC at 1500 RPM, (footnote #2).  To achieve this spec, just use you idle screw to bump the RPM up to 1500, loosen the 10mm nut on the distributor clamp, remove and plug the vacuum line to the distributor, and slowly turn the distributor back and forth until the "Ball" is lined up with the straight edge of the flywheel port at 1500 RPM, (this may take some adjustment to the idle as the distributor advances or retards the timing).  Once achieved, tighten the 10mm nut and reset the idle screw so the car is idling at 900 +/- 50 RPM.  I would then use that fancy timing light to plot the advance curve for your distributor for the following RPM points (1000, 1500, 2000, 2500, 2700) and then compare it to the factory spec curves for the model of distributor you have.  As our Master Tinker points out, if your dwell is fluxuating or your curve isn't in line with the specification for your distributor, it may need a rebuild, (see Overhauling Distributor PDF I downloaded from the FAQ).

 

If your curve plot falls within spec, plug for vacuum line back in your distributor and set your weber carb using the redline spec for achieving best idle.

 

Have fun!

 

Mark92131

 

 

Overhauling Distributor.pdf Dizzy specs.pdf

[RainMoore]

Ok so I realized I was setting the timing at about 950 rpms (so at idle speed). Knocked it up to 1500 and set it at 0 degrees at the little BB, so that should be a 25 degree advance...I think.

you were right about going between the idle and turning the dizzy, thanks for the heads up there.

 

Tom, I upped the advance on the light and found OT at about 12, so I’m running at...37 degrees advance? I’ve confused myself again. I’m sure this will click but right now it seems I’m running in circles.

It sounds happier where it is now that I’ve “properly” set the timing, faltering less and has a steadier run at idle (900-950).

Tho I’ve noticed in the cabin there’s a strangely defending vibration to everything now.

 

It sounds much happier at anything above 1000, and the idle rpms still fluctuate a bit.

When I bump the throttle it will settle below the original idle rpms, then take 60 seconds or so to catch back up. That sounds to me like I need to yank out the dizzy and do some work there. What do y’all think?

oh and the dwell is rock solid at 61 degrees.

Still haven’t figured out the shifter problem, would be nice to pull it out and let it run for a while, not the best ventilation in my garage...

Edited April 25, 2021 by RainMoore