Timing wierdness and questions (1 Viewer)

[Pighead]

Many years ago, i discovered that my Pig ran better with more dizzy advance than the FSM called for. Not an uncommon finding, alledgedly.
My BB disappeared behind the bellhousing and i never saw it again until recently. I would time with the vacuum gauge. Get my best vacuum and back off the advance just a bit. I was getting almost 15 in. Hg at a 700ish RPM idle. At about 5k elevation in Denver.
Then relocated to about 3k elevation and started running stupid Ca gasoline (had been running ethanol free). Figured i better tune for both.
Borrowed one of those new-fangled digital reading out timing lights with a tach and advance functions. Just for fun, tried to determine what i was timed at. So, fiddled with it and brought the BB into the light then to the pointer, red numbers showed 37. What the heck? Add the 7 for the BB and i was running at 44 degrees advance?(!). Is that even possible?
So, i wondered how or if this timing light knew i was running a straight 6 and not a v8. Does it?
My tach has a switch to tell it how many cylinders i got. Not this timing light.
Also, figured out that the inner diaphragm on the 60 series dizzy did not hold air, so i was running only mech advance. Checked the weights and springs and they seemed to move freely, the outer diaphragm holds air and moves the breaker plate to oral suction, so i put the vac line from the carb to it.
Currently timed to 18 or 19 degrees advance at 700 rpm idle, getting only 13" vacuum and it does not tach to 3k (it's redline) like it used to.
So, I'm trying to figure out if i can trust this timing light or go back to old-fashioned eyes & ears and SOP testing. This timing light tach does not exactly agree with in-dash tach.
Figure i need to fix advance diaphragm leak and refurbish dizzy guts too.
Oh, pics. Cuz it happening

 

[B y r o n]

Tach is normally hooked up to coil so it needs to know if connected to 4, 6, or 8 cylinder hence the selector switch. The timing light is normally hooked up to the #1 cylinder and that is all it knows so no need to tell it how many cylinders.

 

[Steamer]

oops, Byron got there first.

I think I have an answer to part of your question. A tach reads the pulses at the coil, so it has to divide the total pulses by the number of cylinders. The timing light reads the pulse on the # 1 cylinder so it doesn’t matter how many cylinders there are.

 

[Pighead]

oops, Byron got there first.

I think I have an answer to part of your question. A tach reads the pulses at the coil, so it has to divide the total pulses by the number of cylinders. The timing light reads the pulse on the # 1 cylinder so it doesn’t matter how many cylinders there are.

Ok, but can it figure out my timing advance accurately as well with just #1 sparkplug wire?

 

[pithicus]

I recently bought the cheapest ebay timing light possible to avoid this sort of confusion that I keep reading about with fancy timing lights.
Sorry , not much help .

 

[73FJ40]

Off a tooth on the distributor?

 

[B y r o n]

Ok, but can it figure out my timing advance accurately as well with just #1 sparkplug wire?

Simply put, yes.

This might help with your other questions.

 

[whitey45]

Are you checking it with the advance at 0 on the timing light? The up and down arrows adjust up and down so you can check at 0, then adjust manually to see how much total you have.

 

[Honger]

I've used my timing light and tac to tune my 40 numerous times.

On this last time I was working on it, after having pulled the distributor completely and having done a valve adjustment, etc; I just timed it by ear/feel. Have been thrilled with the way it's running.

 

[4Cruisers]

The inside of your distributor looks about as clean as any I've seen (that is, before one of my refurbishments ). A new advancer will definitely help the situation.

 

[Pighead]

I recently bought the cheapest ebay timing light possible to avoid this sort of confusion that I keep reading about with fancy timing lights.
Sorry , not much help .

That's the type of light I'm used to, except i didn't get the cheapest one, mine is chrome colored plastic. They kind of lose usefulness after the BB disappears out of the window...

 

[Pighead]

Off a tooth on the distributor?

Nope. One thing i am very familiar with is clocking different dizzys to fit.

 

[Pighead]

Are you checking it with the advance at 0 on the timing light? The up and down arrows adjust up and down so you can check at 0, then adjust manually to see how much total you have.

Yup. Turned the light's advance down to zero, retarded dizzy to get the BB back to the pointer, then advanced the dizzy until the BB eas just on the edge of the window (15ish degrees?) Then trusted the light to set advance about 18 degrees. Now earballing it to advance 2 degrees at a time and running it up a hill or two and listening for pinging. It didn't ping in Denver but sure did here.

 

[Pighead]

I've used my timing light and tac to tune my 40 numerous times.

On this last time I was working on it, after having pulled the distributor completely and having done a valve adjustment, etc; I just timed it by ear/feel. Have been thrilled with the way it's running.

Yup, I'm thinking this is gonna be a long, trial & error tune up.

 

[pithicus]

I tried timing via the timing hole and tdc/bb marks and found it virtually impossible to see properly.
I made a mod . I put timing marks in the harmonic balancer and a pointer made out of tin screwed to one of the timing cover bolts. It makes it SO much easier.

 

[Pighead]

The inside of your distributor looks about as clean as any I've seen (that is, before one of my refurbishments ). A new advancer will definitely help the situation.

Gosh, thank you. High praise indeed. But, in all fairness, i did give it a squirt or two of pb blaster last weekend when i pulled it to check the weights & speings.
Probably more an attestation of the superiority of the large cap dizzy.
I will be needing an advance device of some type, perhaps we can further discuss that elsewhere.

 

[Dizzy]

You can also fire a timing flash with it connected to #6 because that is also on the flywheel mark. That might tell you about the overall precision of the distributor if it is the same as when firing on #1, or not.

 

[fjc-man]

So, who remembers the Jim C thread about the disintegrating, travel limiting, (not metal), bushing that needs to be on the pin I’m pointing at in the bottom of this big cap distributor? If I remember correctly, without it you get way too much centrifugal advance and too quickly to boot. Any of you guys remember where to find this? I’m thinking this could be contributing to Pighead’s problem.

 

[peesalot]

Surprised you didn't have it marked from when you had it here. And no offense, but the tip of your rotor looks like doo - doo. IMO more advance

 

[Pighead]

So, who remembers the Jim C thread about the disintegrating, travel limiting, (not metal), bushing that needs to be on the pin I’m pointing at in the bottom of this big cap distributor? If I remember correctly, without it you get way too much centrifugal advance and too quickly to boot. Any of you guys remember where to find this? I’m thinking this could be contributing to Pighead’s problem.View attachment 2868084

Not me, but I'm gonna take a look at that