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Discussion Starter #1
If anyone can figure this out, this group can! PLEASE forgive my lack of knowledge in this subject as I've only set 8-10 degrees on most engines with the vacuum plugged off. I've built many, many engines (mostly Chevrolet) but never set total timing on any of them. I've never understood it but never took the time to "learn". Fast forward to the last two weeks and I WANT to know total timing. I read every forum until I'm blue in the face. I print out Lars timing procedures as well as Rocky Rotella's. I buy a the Moroso 72310 advance kit (based of off Rocky's reviews and to have on hand just in case) and buy a new adjustable timing light with RPM readout (kinda nice actually).
I unplug my vacuum advance and cap it at the carb.

Start the car and let it warm up. I hit the light on and I'm showing 19 degrees at idle. (?)... 30 degrees at 2k and 40 degrees at 3600 rpm. It just keeps rising and I never did continue with seeing where total timing came in. I should have stopped there.
Due to the advance climbing past 3600 rpms, I change out the distributor springs from stock to the Moroso silver (lightweight). Bolt everything back and hit the timing light to it....30 degrees @ 830 rpms and the total timing peaked at 2600 rpms with 36 degrees set. I know none of this means a lick without my numbers being proper at idle but...?

Another thing I noticed....at 3600 rpm, the balancer mark jumps back and forth slightly (plus/minus 4 degrees). I would think that would stay right still without fluctuations.

My timing gun lead is on #1 ...why is this so off so much on initial timing? I change my timing lights to my old adjustable Craftsman and it reads the same. I am at a loss as the car drives beautiful! It had a tendency last summer to get warm in traffic, hence the crash course in timing and the jump into a part that I've always shyed away from (total timing).

Please don't destroy me with 'you're-an-idiot' comments but help me get a clue into what is going on! Thanks everyone!!!

This is a rebuilt (maybe 400 miles on it) stock '67 400 Pontiac with an 068 cam, points distributor (new stock replacement) with Petronix installed.
 

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"...40 degrees at 3600 rpm. It just keeps rising and I never did continue with seeing where total timing came in...
Due to the advance climbing past 3600 rpms, I change out the distributor springs from stock to the Moroso silver (lightweight). Bolt everything back and hit the timing light to it....30 degrees @ 830 rpms and the total timing peaked at 2600 rpms with 36 degrees set..."


Yeah, I can see why you'd be puzzled. I can't see any reason why using lighter springs would decrease your total mechanical advance. I did read that you should never use the lightest springs that come in those spring assortments. You can experiment with the others. Some say they used one stock spring, and one of the kit springs, to get their desired advance curve.

But, I can say I think 30 degrees is too much advance @ 830 rpm. Most seem to like somewhere between 12 & 18 degrees, at idle, then begin to increase above 1000, with all the mechanical being in by 3000 or a bit less. Most(but not all) engines seem to like around 34-36 degrees total mechanical advance.

I've read that some dist, especially the HEI, can seem to be through advancing, but then advance a little more as rpm increase. Sometimes this can be caused by worn advance weight pivot posts, among other things.

If when the initial advance is where you want it, the total is too high, you can install a positive advance stop of some kind, which will limit the amount the advance weights can increase timing. I made a stop for my HEI with just a simple screw, in one of the extra holes in the bar which the rotor attaches to. There are several ways to make stops.

Hey, good luck with your tuning ! Maybe some of these other guys can help solve your problem.
 

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Discussion Starter #3
Thanks BigD. I will change out the light springs and experiment around with all in at 3500. I'm guessing the new initial timing is due to the mechanical advance having those light springs and advancing early. But...is it normal for initial timing to be at 19 degrees? Seems awfully high in comparison to my past cars (8-10 initial).
 

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lil65,..I think you are doing pretty good don't be so hard on yourself....

1) base timing you set with your hand at timing mark,.... fixed
2) Centrifigal from weights RPM dependent
3) vacumn from vac can

OK so you say you got 36 total, what was base and what was centifigal?

you want to find centrifigal and it can be reduced by turning the points dist upside down on the workbench and lookin at the little slot that moves back and forth when you move the weights....

a brass collar on that pin usually in the curve kit will reduce it.

so say you have 24 centrifigal....then set base with your hand to 12...total 36

if you have 26 centrifigal set base to ten.....

if you have 30 or 32 centrifigal, then reduce it with the brass collar.

once that set, you can use a silver and blue spring to get your curve in say to 3000 to 36....

get a B26 vacumn can auto parts store; a BWD 375..... would work, and then get a vacumn corrector from Lars.....put that can in and the corrector ...

google...."How to optimize the centrifugal advance in Pontiac"....

you can then check your centrifigal advance with a protractor.....

make sure to connect your vac advance to full manifold vac so you are getting 20 to 22 advance at idle with vac connected after all said and done..

that will give you 46 to 48 timing at light throttle cruise.....smooth and run cool....

I put dist on my Sun Dist macjine, they are all off even new out of the box ones..... not unusal to see 32 degrees even more on centrifigal...from wear. and some were set that way from factory to have 32 and set timing at 4 degrees...ggreat for emissions, bad for driving!

good luck you will get it!:nerd:
 

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Discussion Starter #5
Thanks Lemans guy. They say this isn't rocket science but there most definitely is a science to it! :)
I thought you achieved 36 total through total timing and combo of advance springs and didn't concern yourself with initial timing after that. I will keep at it and see what I can do tonight!
 

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it is confusing......

here is how I do it....forget the springs in this early part....

I find the most critical unknown......"Total Centrifigal advance"....

once you know that, you subtract that number,....say 26 from 36 to get your base setting number....you set base with your hand....

in this example 10...........................then .....26 + 10 = 36 Total timing.

Total timing is really shorthand for "Total Mechanical Timing" that is

Base + Centrifigal....vacumn advance is not considered part of it.....

with your timing light, you can do this....

vac removed and plugged set base timing to 10....

turn off car...

remove dist cap and take off one spring, replace cap...

hook up timing light....start car and rev up to timing stops...

it will come in early with one spring....say before 3500 rpm's or so....

now subtract your 10 base, and what you have is your centrifigal....the starting point...

so if you got 40......-10.....your centrifigal was 30.....you adjust that down with the brass collar.....

don't forgret to replace the spring......

springs do not effect total advance, only the rate it comes in....:nerd:
 

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Discussion Starter #8
OK...Good changes here!

I immediately pulled out the lightweight springs (which were actually gold in color) and the stock weights. I then replaced them with the Moroso weights and went to the medium springs (silver). This is what I got:
8 degrees @ 750 rpm
15 degrees @ 1500 rpm
19 degrees @ 2000 rpm
24 degrees @ 2500 rpm
27 degrees @ 3000 rpm
30 degrees @ 3500 rpm

I am guessing that my weights were sticking or binding? I went from 19 degrees at idle to 8 degrees after changing the weights.

I then removed 1 medium spring (silver) and installed 1 light spring (gold). This is what I got:
8 degrees @ 750 rpm
18 degrees @ 1500 rpm
22 degrees @ 2000 rpm
27 degrees @ 2500 rpm
30 degrees @ 3000 rpm
33 degrees @ 3500 rpm

I then adjusted the distributor, at idle, from 8 degrees to 10 degrees and this gave me 38 degrees at 3500 rpm. I also noticed that my vacuum gauge was registering 15....I've never known either of my Pontiac engines to register that high. Woohoo.

Do these numbers look acceptable or should I be trying something/changing something else?

Thanks again!
 

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That is improvement,...so it appears you have Centrifigal advance of 28 degrees.....you should set your base then to 8 to give you 36 total. You can try 38.... but you have to make sure you have no spark knock. I would go with 36......8. + 28...

Your spring curve looks fine, that will really make the car run good and you have a smooth curve. Other guys try to get it lower, but you can get spark knock through the range at different RPM's if you want to spend hours doing that. I would leave it there.

Next I would get rid of the vac can that came with the distributor, get A BWD 375 marked on the can B26. That has a tattoo vac timing of 16....still too much. So email Lars and get one of his Vacumn correctors, put the B26 and the Vacumn corrector in. It limits it to 10 to 12 advance from vac.

You will then have 46 to 48 at light throttle cruise, perfect for today's gas.

So 8 Base,....28 Centrifigal = 36 total mechanical. 10 to 12 more from the vac as described....46 48

The light springs bring you all in by 3500.

Lastly make sure you hook Dist vac to Full manifold vac,....that way you will get 8 Base and 10 to 12 vac advance at idle.....18 to 20....

That will give you great idle cooling, 8 degrees won't and that is what you will have if you use ported vac.....

Nice work....you will notice the difference especially when you barely touch the gas to go,....try light pedal gradual acceleration....really nice fast and smooth....

Timing is everything!
 

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Ps 65,.... make sure you don't confuse your springs with total Centrifigal advance........

For example you could have 36 total at 3500, but if it went up as you go to 5k or 6k, .....then 36 is not total Centrifigal.....

Total Centrifigal is when the weights stop advancing, minus the base setting. If you are sure that is 28....you said it was 38 when you had Base at 10......then that is the end...no spring will make it go past 28....it is the end.....

The springs then just determine how fast it gets to the end,.....say it gets there at 3500.

Also two silver springs and all in at 3000 would be a great curve. I would use that first, and as long as no knocking would prefer it....

Either spring combination will work as long as total is right,...total is critical.....so make sure that it stops, I outlined a way to do that in earlier post

Good work, you will really appreciate it when you are driving, better gas mileage more power, better cooling, better throttle response....
 

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"...so make sure that it stops..."


This is important !!!

According to your 2 sets of figures, the weights apparently had not stopped advancing the timing, at 3500 rpm, with the 1st set of springs you tried.

So, with the last set of springs you tried, did the timing quit advancing past 3500 rpm ? Or did you even check it past 3500 ? The weights must hit a positive stop, at some point. The point at which the weights hit the positive stop is your max mechanical advance. The springs only determine the rpm at which the weights hit the stop.

As mentioned earlier, you can remove one spring entirely, for testing. This will allow the weights to reach max advance at a much lower rpm(assuming they move freely without any binding). When you set the max advance where you want it(usually between 34 & 36 degrees), THEN you can try different spring combos to get that max advance to come in at the rpm you desire(usually around 3000rpm).

If the weights have hit the stop, then the timing will not advance any more, as the rpm increase past that 3000 rpm mark. Or, in other words, when your engine revs up to 4000 rpm, the max total mechanical advance will still be exactly what it was at 3000 rpm. And the same is true for 5000 rpm. The advance should hit the stop at the rpm you set, with the springs, then not advance any farther, regardless of how high you rev the engine.
 

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Discussion Starter #12
As I lay in bed last night I got thinking, "I never did see where the total stopped". I'll try again tonight and repost what those numbers were. Thank you all again, I truly appreciate your patience!
 

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65...you are close. Big D is spot on......I put those curve kits on distributors and spin them on my sun Distributor machine, sometimes I keep original weights, they are very good ...sometimes need a change

this is on both originally points dist,...yours,...and HEI's.

So if your posts are not warn I would not be surprised to see the curve kit give you 28 or so. So as we said you have to start all this process with the foundation.....

What is the max Centifigal advance?........without that number, everything else is messed up.

once known you adjust accordingly by weight changes, as from curve kit, or collars underneath, or some stops above like Petronix Distributors (not petronix insert kit like you have)

then easy subtraction for base, get your vac can right, one that pulls in below your idle vac, yours is 15 hg, the B26 can will work great with the vacumn corrector...

you can have much less if you are using full manifold vacumn, vac advance will be all in at idle....what you want

springs, I have put them in Corvettes all in by 2500 RPM.....3500 is ok.

shoot for 3000, but you might hit 3200, the spings and weights all vary a tad as does the distributor.....2500 is usually too quick and can cause knocking thru the RPM range,.....stay closer to 3000 and you will run great, but a little over or under is ok.

Total is critical, 36 perfect on today's gas.....range could be 34 to 38....but make sure no knocking at 38. or even 36....you want it at peak just below knock.....

I think you are doing great, once you get it right you will know....good to have a new dist also, many have too much play in the shaft and that effects timing.:nerd:
 

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Discussion Starter #14
It is a new distributor (Cardone?) so posts should be good. I will remove 1 spring and see where it maxes out and make adjustments with springs from there. I will post results once I do. Again, thank you!
 

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"...get your vac can right, one that pulls in below your idle vac, yours is 15 hg, the B26 can will work great with the vacumn corrector..."



I know very little about the vac cans. My engines were mostly race only. So, I didn't hook up the vac can. But, I have seen the Crane adjustable cans recommended. My thought about vac advance is that it is probably better to err on the low side. With today's gas, its real easy to get detonation. Would be a shame to have the mechanical curve just right, then have too much vac advance cause damage.

https://www.summitracing.com/parts/crn-99601-1
 

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Discussion Starter #16
Ok...here is what I did tonight.

1) I pulled 1 spring from the distributor and it is all in @ 4400 rpm
2) With the spring still removed, I set and lock the distributor down at 36 degrees with the timing pegged
3) I reinstalled the spring and timed again:
4 degrees @ 750 rpm
12 @ 1500
16 @ 2000
20 @ 2500
23 @ 3000
26 @ 3500
4) I reset timing back to 8 degrees due to hard start condition with 4 degrees.

I will install a new vacuum canister but that'll take a bit to get my hands on and I'm struggling now without tossing in another monkey into the mix. Am I close enough with this combo? The white flag is being raised.
 

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Yeah, something don't sound right.

(1) I'd think that with only one spring, unless that spring is excessively strong, the weights should move out to max advance, well below 3500 rpm.

(2) So, I'm thinking there has to some logical reason why it takes til 4400 rpm. So, I'd remove both springs, and check the movement of the weights, by hand. They should move smoothly ALL THE WAY to full advance, without any binding. Obviously, if there is binding or any type of stiff resistance, without springs, it will be even harder for the weights to achieve full advance, with the springs connected. If there is stiff resistance, find out why & fix it.

(3) If there is no stiff resistance, then some combination of heavier weights and or lighter springs should achieve max advance by 3500 or lower. If there is no stiff resistance, you might first try no springs at all. This SHOULD result in max advance well below 3000 rpm. If not, there is not much use in adding springs, since they will only raise the rpm at which max advance is reached. Heavier weights SHOULD advance to max, at a lower rpm--assuming they can move freely, all the way to the max advance position.

(4) But, if using no springs at all does achieve max advance below 3000, then you can try adding one light spring, and checking that. Keep adding spring pressure IN SMALL INCREMENTS, til max advance is reached at around 3000 or no more than 3500.

(5) NOW, only AFTER max advance is set where you want it(usually 34-36), can you set initial advance(advance at idle). This is where the POSITIVE STOP comes in. If you want 36 degrees, all in by 3000, and 12 @ idle, then you MUST have a positive stop of some kind, which will limit the total amount of mechanical advance to 24 degrees. 12 initial @ idle + 24 mechanical advance = 36 degrees total advance. There are several ways to make a positive stop. The actual type of stop is not that important. The important thing is that you DO have a stop, and that it is adjusted to allow the exact amount of mechanical advance you want. This is all involved in what is called "dialing in your curve".
 

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I agree, something's not right here.
Couple things come to mind. Are you positive the timing light you're using is good? If the light is lying to you, you don't stand a chance.
Thing 2: Cardone is going to be a rebuilt unit, not new. In my mind rebuilt parts are always suspect because you never really know what kind of work the guy did that day. If you've got "too much" mechanical advance in the unit, then my first suspicion would be that the guy either used the wrong bushing on the limit pin, or left it out altogether. To check that, the distributor has to come out again. Drive out the rolled pin that holds on the drive gear so you can pull the shaft out (be mindful of the thin washers/spacers so you can put them back as they were). When you look at the "bottom" side of the advance mechanism you should see a pin sticking through an oval shaped slot. It should have a small bushing on it. This pin and the size of the bushing on it together control how much the advance mechanism can move. The larger the bushing on the pin, the less travel it has in the slot, and the less mechanical advance you'll have. The pin also provides a positive stopping point in both directions of travel so that your timing can be consistent. I've seen it happen before where these pins get broken off. When that happens, there's nothing to limit travel in either direction and you'll see some very strange things happening when you try to adjust your timing.
You can see what I'm talking about in this photo, along with samples of different sized bushings.


Bear
 

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Bear beat me to it. You don't lock down the distributor to set/limit your total mechanical advance as you did when you locked it down at 36 degrees. This affects your initial timing as you found out. Then moving it back to 8 degrees advanced the total an additional 4 degrees putting it up to 40 degrees total.

"A timing slot in the mechanical-advance mechanism limits total engine timing advance by using a pin inside a slot. In order to increase an engine’s total timing, this slot must be elongated with a carbide cutter. If the total timing needs to be limited, the slot will have to be welded shut. Many aftermarket distributors (such as MSD) supply offset bushings that allow the total timing to be increased or decreased without any cutting or welding."

The photo Bear provided comes from an internet article. You can see the limiting pin sticking through the oval slot. These pins can have a rubber bushing from the factory and do deteriorate and break off. I suspect your rebuilt distributor may not have had this bushing replaced, but you won't know until you look. I am no expert, but have also read that the slot in the plate can also be application specific to whatever engine came in the car to adjust total mechanical advance. An LS-6 454 will need a different timing curve than grandma's 195HP 283 engine.

So, to limit the total advance, you need some type of stop. So set your initial timing (idle) where it seems to start/idle the best. It may be 8 or as high as 12 degrees. From there you then will adjust your total mechanical advance as has been already well explained, using the assorted springs & various weights to bring in a timing curve that works for your application, but limiting total mechanical timing in the 32-36 degree range. "A good rule of thumb is that the higher the engine’s compression ratio, the less total timing it can use before detonation occurs. Also, a higher octane fuel is required for the engine, to help control detonation. Low octane fuels ignite faster, thus require less timing advance. Conversely, high octane fuel can handle slightly more timing advance."

bigD has already mentioned this in checking total mechanical advance, but here is another mention of doing this, "1-remove advance weights and reinstall the springs with no weights. run ening at idle and mark actual timing . 2-remove springs and install weights and run engine up with no springs. Degrees shown on balancer would be your maxim timing advance"

Once you know what the total mechanical advance is, which you may find to be 40-44 degrees as I believe you may have mentioned earlier, you then want to use some form of limiter stop that will prevent the total advance from going past the 32-36 degree range. As seen in the photo, one form of stop is to use a replacement bushing which is larger in diameter than the original rubber bushing as the larger diameter then limits the amount of travel within the slot (which is what limits your total mechanical advance through the weights/springs as the distributor spools up to higher RPM's). The bushings come in assorted diameters to fine tune your total mechanical advance. From what I have read, never doing this myself, is that the down side is that the bushing is under the plate as shown in the photo and this requires you to disassemble the distributor in order to insert the push-on bushing (which I have read needs to be additionally Lockited into place). I am sure each sized bushing diameter has a known effect on limiting the total movement of the pin based on its diameter size chosen. Aftermarket distributors make this much easier as they design for this and provide easy access for doing this as well as the assorted bushings to dial in the distributor. Most of the bushing kits seem to be for the HEI distributor, so I don't know if these will work or can be made to work for your points distributor.

There are other ways to limit the total mechanical advance which can be found on the internet, but the bushings seem to be the best way to go. Found this neat article on setting the total on a Pontiac points distributor. It also has photos to show how to do this: How to Optimize the Centrifugal Advance in Pontiacs - High Performance Pontiac - Hot Rod Network

Once you get your mechanical advance squared away, then you can tackle the vacuum advance part of the timing.
 

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right..you don't lock down 36......you ste timing at 10 base vac removed...

remove spring and read timing from light to when it stops advancing....forget RPM's for now

you just want to know when it stops advancing..what is the timing number there?

say it is 40....then subtract the 10 you have 30 centrifigal....

you can do nothing without knowing this number.....
 
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