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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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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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Discussion Starter #67
Car is running like a scalded cat!!! Long story short there were several issues masking each other... Timing is at 12 initial, 22 with vacuum and 30 total... used new weights, new vacuum can and two different springs, all as suggested earlier.

I'll detail the all the issues on my main thread...

It's almost not fair to my B.F. Goodrich tires... I can burn rubber without a brake stand and keep it going as long as I can (I have an automatic) until she shifts into high gear...

Thanks for all your help!!!

Dan
 

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I would turn that base timing up 4 to 6 more degrees......giving you 16 or 18 base and 26 or 28 at idle.....with total timing then at 34 or 36.....it will run even better...

just make sure that your total numbers are accurate and you get no pinging.......
 

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Discussion Starter #69
Thanks for the information Lemans Guy... I'll try to make the change my riding season ending very soon and fall/winter hobbies are poised to fill the slot. ;)

Question: If it pings is it only timing related or fuel etc??? If timing just back out the timing? I've had "three" pings in the past and it goes away as I accelerated "through it". I assume you mean pinging all the time under heavy load.

Thanks again and in advance, Dan
 

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Dan, yes pinging is the sounds detonation makes in the cylinder when the fuel/air mixture fires oof at the wrong time. Here we are talking about too early as you advance the timing.

it is basically the piston wobbling in the cylinder and the mixture fuel air explosion “ringing the bell” of the metal engine. When timing is set right the spark ignites at the right millisecond and powers the piston down without a wobble and without an inefficient power stroke.

so folks say what is perfect timing on our 60’s V8’s.......optimal for most power and efficiency and cooling......is two degrees below detonation!.....that is the most for power and efficiency and smooth running.

so I set distributors to start with at 36 total timing.....and go from there. Most engines take it, but if any pinging retard the base timing 2 degrees and recheck. If still there retard two more degrees and recheck, until the pinging is eliminated.

Now some Pontiac can even take 38 or 40 but be careful as that could cause detonation. Some guys like 34 degrees to start. But if you set it at 36 for street performance and no pinging that is agood place to be with your numbers.

also as that total comes in it can ping as you accelerate. This happens when there is too much advance as you sweep up the power. It happens from too aggressive a spark curve, trying to get it all in real low and or a vac can with too much timing in it. Many I see have 20 or 25 in a vac can way too much.

your number sound ok just be sure of the goal and just dial it up a bit, and test. I don’t recall when you said your total was all in but 3000 or 3200 is good, you don’t have to have 2500..

that is real aggressive and will mean light spring and sometimes centrifugal advance coming in on top of your idle timing. You don’t want that.
 

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Discussion Starter #71
Great info thanks LG! That helps a ton.

I may have to change out the weight springs - I think the timing may be advancing too fast (I remember all-in at 2,750 so I'll have to double check). I used one light and one medium as you suggested previously.

Hopefully I can bump increase the timing a bit and test it but they are calling for temps in the 30s here this week. :(

I also have to wait until my vacuum system repair parts arrive - hose, check valves, etc... Should be here in the next few days. I need to fix the vacuum so I don't chase the timing setting - like I did before I fixed what I've done so far. I suspect I am still getting erroneous or inconsistent timing values because of the leaks - for example, after a long run the engine idle changes (rises) between warm up and return (about 2 hrs later). I want to fix all vacuum issues so I can set the timing with no "outside" influences.

Thanks again.
 

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Discussion Starter #72
P.S. Guy that helped me set timing says total timing came in at 2700.
 

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You can leave it at 2700,......just drive and make sure it does not ping.......Younare looking for somewhere between 2500 to 3500...with no pinging....lower is more aggressive but ok as long as no pinging and it does not bring centrifugal in on top of idle...

in other words it ends at 2700 but when does it start,..this is centrifugal advance....so something to look for
 

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2700 is very quick with today's gas. It's great if it doesn't ping, otherwise change the lighter springs on the advance weights for heavier ones.
 

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Discussion Starter #76
Thanks OMT, much appreciated! I have to find the box/specs to see what springs bring it in later so I know what I have. Between family stuff and such I have a short memory when it comes to the car stuff. :)

If it runs as good as it does now I can't wait to make it run even better!! Hope winter holds off a few more weeks. ;)

Dan
 

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Discussion Starter #77
Found it...

RPM 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
Spring
LIGHT (Copper) 0º 10º 20º 22.5º 23º 23º 23º 23º 23º 23º 23º 23º 23º 23º 23º 23º
MEDIUM (Silver) 0º 0º 6º 13º 19º 23º 23º 23º 23º 23º 23º 23º 23º 23º 23º 23º
HEAVY (Gray) 0º 0º 0º 6º 10º 16º 21º 23º 23º 23º 23º 23º 23º 23º 23º 23º

I'm in the middle of the highlighted zone...

I'm using one LIGHT and one MEDIUM spring hence being between 2500 and 3K.
 

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Right a good place to start, it gets you close but you need to make sure it does not ping and you also need to verify it with a timing light. Then you will know what it actually is

those springs vary a lot, the chart is not a super accurate measure.
 
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