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Discussion Starter #61
Let’s restart. You want total timing to be 36 BTDC. Total timing does not include vacuum timing. Total timing is not tied to any RPM’s.

It is the total amount that your timing can advance at WOT. When no vacuum is present. Total timing is a combination of base timing, set with your hand and timing light, and the centrifugal timing advance by the weights. Springs don’t matter here.

it is how far the weights will advance, and then stop by hitting their hard metal stop.

base timing and centrifugal timing must be matched to achieve 36 degrees. So if your centrifugal total is 24 degrees you set base timing at 12 degrees =36. If centrifugal 26 set base at 10 = 36.

Now vacuum timing, Vacumn timing is a great benefit to make your car run cooler smoother and better accelerate. It adds the necessary advance above total timing, 10 degrees is perfect, for all that benefit.

the reason you need it is at idle and cruise the mixture is leaner and needs spark much earlier to get a complete burn.

use the vac can I told you hooked to full manifold vac.

Now the springs and how everyone talks this advance shorthand wrong. ”I got 36 degrees at 2500 RPM” they say. So I am good. If that is your total timing you are good, but if your timing advances beyond that to 49 degrees at 4000 Rpm.. you are not good.... as you are not reading total timing just springs at various times.

once your total timing is established, then you can adjust when it comes in at what RPM with springs. You want to bring it all in near 3000 or so 32 3400 even for good running.....

springs are meaningless until all other parameters established.

Base Timing is set by hand and locked down. Centrifugal timing is Weights and springs and Operates on RPM’s only.

Vacumn timing is tied to your gas pedal...light load, more timing, pedal down WOT no Vacumn timing.

you will get it, think about the 3 methods of timing at play...base, Centrifigal and Vacumn.

sync em all up and it will run great!
OK, that makes sense now. Thanks for the clarification - not the relationship between the advance types. Thank you very much!

Weights will be here Saturday, vacuum can Sunday and vacuum tubing tomorrow. Found another leak today!! I'm replacing every vacuum line I can.

I will let you know how it goes.

Thanks again! Dan
 

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Check it, it tells you what it really is. That is also the timing when you set your carb idle circuit. So that is where it runs.
I'll probably eventually get to it, once I get it back together. Right now I'm hearing that there's an 8 week lead time on a set of pistons though so it's not going to be soon.
 

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Yeah everything has slowed down, you will get er done eventually...sounds like it will be a great one.
 

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OK, so I understand...

I know the springs control how fast the mechanical timing comes in… Also understand ported versus manifold vacuum.

If I want to get a total timing advance of 32-35 (engine builder said it should like that) I can reach that by using vacuum advance and mechanical methods.

I.E. If I use Ported Vacuum I set the base timing at 12 degrees (idle timing), Vacuum kicks in at a predetermined RPM (current vacuum canister is a 20 degree advance can) so I get 22 degrees then at a predetermined RPM the vacuum drops off and the weights are supposed to take over. Weights are currently setting my advance to 49 degrees which is too high - adding 27 to the vacuum advance. This means I am adding 27 degrees mechanical and the weights are traveling too far out (hitting my old rotor) for what I need - obviously since I’m at 49 degrees in the current setup.

So, if I get the 8-12 degree vacuum can which usually pulls 10 degrees advance and use manifold vacuum which gives me vacuum full time I set my base timing at 12 degrees and the vacuum can pulls 10 more for 22 total…

How many degrees will I get form the new weights suggested?

Thanks for your help!!
Timing is set with the vacuum advance disconnected and plugged. "Total" timing is initial plus centrifugal, and should be in the 32-36 range. The RPM must be high enough that the centrifugal advance is "all in". With stock springs, this may be as high as 4000 RPM. Lighter springs bring the advance in sooner; it may be all in as low as 2000 RPM. Rev the engine while watching the timing; when it quits changing, you're there!

Vacuum advance provides additional advance at part throttle (cruise). At full throttle, vacuum goes away, and vacuum advance goes away. If your car runs smoothly at full throttle, but rattles (detonates) at part throttle, you have too much vacuum advance. Less than stock vacuum advance is probably a good thing with today's gas.

So 40-50 degrees advance with vacuum advance connected is not a problem.
 

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Discussion Starter #66
Timing is set with the vacuum advance disconnected and plugged. "Total" timing is initial plus centrifugal, and should be in the 32-36 range. The RPM must be high enough that the centrifugal advance is "all in". With stock springs, this may be as high as 4000 RPM. Lighter springs bring the advance in sooner; it may be all in as low as 2000 RPM. Rev the engine while watching the timing; when it quits changing, you're there!

Vacuum advance provides additional advance at part throttle (cruise). At full throttle, vacuum goes away, and vacuum advance goes away. If your car runs smoothly at full throttle, but rattles (detonates) at part throttle, you have too much vacuum advance. Less than stock vacuum advance is probably a good thing with today's gas.

So 40-50 degrees advance with vacuum advance connected is not a problem.
Thanks for the info Montreux. Much appreciated!
 
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