Is Centrifugal timing set with vac. can. disconnected and plugged? I keep reading all these articles, and I see where initial timing is set disconnected and plugged, but I'm confused on centrifugal.

 

Centrifugal timing is not "set"
It is checked, and or changed with weights and springs.

I.E.

700rpm 0 cent advance
1600 10 deg adv
3200 24 degs /all in, meaning the plate has advanced as far as it can.

 

Centrifugal advance is not "changed" with weights and springs. It is curved. You can re-curve it to come in later or sooner in the RPM range with weights and springs, but the total amount of advance is fixed. To "change" it, you will need to shorten the slots with welding or buttons to reduce the total amount, or grind or file the slots longer to increase the total.

 

I think when you say the centrifugal you mean the combination of initial AND centrifugal which is usually referred to as the Total timing.
So yes disc and plug the vac line on the dist vac can.
Set your total ;( for instance 36 degrees all in by 2800 rpm.)
When you bring the rpms back down to idle the timing light will now show you your initial timing.

 

Guy has no knowledge about setting cent adv timing and you give me the
"its called curve" speech?

 

I think we found out who has no idea about setting "cent adv timing". Didn't you [I]JUST[I] say it wasn't set? Are you for real?

 

Thanks guy's, now I have a better understanding of how it works. I set the initial at 14* and adjusted the vacuum canister to add 16*. I changed the springs to 1 blue and 1 white Accell. I didn't have anyone around to watch the tach. so I'll be testing it out. What do you thick?

 

No, are you?
All in timing?
I bow to your master skills.

Curved

Please school us about it.

 

Please clarify your question, I'm having a little trouble with your gibberish.

 

No doubt, try adding to the OPs question.
You found it necessary to correct my explanation about CT.

Now, what is wrong with my post to the OP?
I did not use the term curved?
I did not tell him what All in timing is and pick a advance number
for him?
I gave a simplistic explanation about CT.
He now can use that info to do whatever he wants.

You chose to nit pick at my post.

How does he know what he has unless he checks it?
You post to show how smart you are and how wrong I was, so I ask you to school me.

 

 

Still adding to the OPs question I see.

 

And you are? Another self righteous asshat.

 

Still waiting for your expert reply to the OP.

 

Right there in post three, feel free to read it when you grow up.

 

Centrifugal (aka mechanical) advance is determined by distributer rpm. It is generally 0* at low rpm (500-800) and increases as rpm increases. The amount of cent advance is fixed in each distributer; it is modified by physically changing the size of the slot. Most stock "curves" are good but a little slow. One lighter advance spring will bring it in quicker. In CA we have crappy 91 octane premium ($3 per gal); with high compression and iron heads I have to watch spark lead!
Vacuum advance is based on vacuum, either ported (zero @ idle) or manifold (full @ idle). As the carb throttle plates are opened, they operate the same. High vacuum equals low engine load, which can tolerate more spark lead and leaner mixtures. Low vacuum equals high load conditions which does not tolerate as much lead and needs richer mixtures.
Treat each as separate systems. Total advance is (centrifugal + initial). For example, my 68 L36 stock distributer has 32* mechanical, and the stock initial timing is 4* btdc. So it has 36* total. I bring it in quicker with 1 lighter spring. And I limit vacuum to about 12*. It is kinda hard to have full vacuum and full centrifugal at the same time, because you would need low engine load and sufficient rpm. Curise on the freeway will do it, though.
I suggest getting a timing tape and plot your curve at each 500 rpm or so. Start with centrifugal only (vacuum plugged). Then add in vacuum. Do some testing; that's what hot rodding and Corvettes are all about. Anyways that's what I do...

 

In answer to the poster's question: Pull the hose to the vacuum can and plug the hose. Then you can evaluate the mechanical advance system in the distributor. You either need a "degree tape" to put on your harmonic damper (so that you can measure timing advance/retard) or you need a dial-back type timing light. With vacuum advance OFF, check initial timing at idle and record that along with the engine rpm. Now increase throttle at various rpm levels (i.e. measure timing and record it at every 500 rpm increment) until the mechanical advance no longer changes...that is where the mech advance is "all-in". What you would like to obtain is 32-36 degrees of mechanical advance for the "all-in" condition when your engine is turning 2800-3000 rpm. You can change the 'slope' of the mechanical advance curve [or line] by swapping out the springs on the distributor flyweights. Softer springs allows the "all-in" condition to occur at a lower rpm setting. {Note: There are other adjustments that can be performed with the distributor mechanisms, but that's too much to discuss here.} Once the proper mechanical advance is achieved, re-plumb the vacuum advance, run rpm up to full mech advance setting and measure "total" advance. If it is under 54 degrees you should be good-to-go.

 

Thanks again.

 

Engine is runing great, sounds good, and I'm smiling.